Use ariadne

https://github.com/casey/just/issues/1323

.github/workflows/release.yaml

@@ -110,7 +110,7 @@ jobs:
       shell: bash
 
     - name: Publish Archive
-      uses: softprops/action-gh-release@v2.0.8
+      uses: softprops/action-gh-release@v2.0.9
       if: ${{ startsWith(github.ref, 'refs/tags/') }}
       with:
         draft: false
@@ -120,7 +120,7 @@ jobs:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
     - name: Publish Changelog
-      uses: softprops/action-gh-release@v2.0.8
+      uses: softprops/action-gh-release@v2.0.9
       if: >-
         ${{
           startsWith(github.ref, 'refs/tags/')
@@ -157,7 +157,7 @@ jobs:
         shasum -a 256 * > ../SHA256SUMS
 
     - name: Publish Checksums
-      uses: softprops/action-gh-release@v2.0.8
+      uses: softprops/action-gh-release@v2.0.9
       with:
         draft: false
         files: SHA256SUMS

Cargo.lock

@@ -84,6 +84,16 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "ariadne"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44055e597c674aef7cb903b2b9f6e4cba1277ed0d2d61dae7cd52d7ffa81f8e2"
+dependencies = [
+ "unicode-width 0.1.14",
+ "yansi",
+]
+
 [[package]]
 name = "arrayref"
 version = "0.3.9"
@@ -524,6 +534,7 @@ name = "just"
 version = "1.36.0"
 dependencies = [
  "ansi_term",
+ "ariadne",
  "blake3",
  "camino",
  "chrono",

Cargo.toml

@@ -19,6 +19,7 @@ members = [".", "crates/*"]
 
 [dependencies]
 ansi_term = "0.12.0"
+ariadne = "0.4.1"
 blake3 = { version = "1.5.0", features = ["rayon", "mmap"] }
 camino = "1.0.4"
 chrono = "0.4.38"

GRAMMAR.md

@@ -90,7 +90,13 @@ import        : 'import' '?'? string? eol
 
 module        : 'mod' '?'? NAME string? eol
 
-expression    : 'if' condition '{' expression '}' 'else' '{' expression '}'
+expression    : disjunct || expression
+              | disjunct
+
+disjunct      : conjunct && disjunct
+              | conjunct
+
+conjunct      : 'if' condition '{' expression '}' 'else' '{' expression '}'
               | 'assert' '(' condition ',' expression ')'
               | '/' expression
               | value '/' expression
@@ -116,7 +122,7 @@ string        : 'x'? STRING
 sequence      : expression ',' sequence
               | expression ','?
 
-recipe        : attributes* '@'? NAME parameter* variadic? ':' dependency* eol body?
+recipe        : attributes* '@'? NAME parameter* variadic? ':' dependencies eol body?
 
 attributes    : '[' attribute* ']' eol
 
@@ -128,6 +134,8 @@ parameter     : '$'? NAME
 variadic      : '*' parameter
               | '+' parameter
 
+dependencies  : dependency* ('&&' dependency+)?
+
 dependency    : NAME
               | '(' NAME expression* ')'
 

README.md

@@ -161,7 +161,7 @@ most Windows users.)
     </tr>
     <tr>
       <td><a href=https://nixos.org/nix/>Nix</a></td>
-      <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix>just</a></td>
+      <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ju/just/package.nix>just</a></td>
       <td><code>nix-env -iA nixpkgs.just</code></td>
     </tr>
     <tr>
@@ -268,7 +268,7 @@ most Windows users.)
     <tr>
       <td><a href=https://nixos.org/nixos/>NixOS</a></td>
       <td><a href=https://nixos.org/nix/>Nix</a></td>
-      <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix>just</a></td>
+      <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ju/just/package.nix>just</a></td>
       <td><code>nix-env -iA nixos.just</code></td>
     </tr>
     <tr>
@@ -1290,26 +1290,61 @@ Available recipes:
     test
 ```
 
-### Variables and Substitution
+### Expressions and Substitutions
 
-Variables, strings, concatenation, path joining, and substitution using `{{…}}`
-are supported:
+Various operators and function calls are supported in expressions, which may be
+used in assignments, default recipe arguments, and inside recipe body `{{…}}`
+substitutions.
 
 ```just
 tmpdir  := `mktemp -d`
 version := "0.2.7"
 tardir  := tmpdir / "awesomesauce-" + version
 tarball := tardir + ".tar.gz"
+config  := quote(config_dir() / ".project-config")
 
 publish:
   rm -f {{tarball}}
   mkdir {{tardir}}
-  cp README.md *.c {{tardir}}
+  cp README.md *.c {{ config }} {{tardir}}
   tar zcvf {{tarball}} {{tardir}}
   scp {{tarball}} me@server.com:release/
   rm -rf {{tarball}} {{tardir}}
 ```
 
+#### Concatenation
+
+The `+` operator returns the left-hand argument concatenated with the
+right-hand argument:
+
+```just
+foobar := 'foo' + 'bar'
+```
+
+#### Logical Operators
+
+The logical operators `&&` and `||` can be used to coalesce string
+values<sup>master</sup>, similar to Python's `and` and `or`. These operators
+consider the empty string `''` to be false, and all other strings to be true.
+
+These operators are currently unstable.
+
+The `&&` operator returns the empty string if the left-hand argument is the
+empty string, otherwise it returns the right-hand argument:
+
+```justfile
+foo := '' && 'goodbye'      # ''
+bar := 'hello' && 'goodbye' # 'goodbye'
+```
+
+The `||` operator returns the left-hand argument if it is non-empty, otherwise
+it returns the right-hand argument:
+
+```justfile
+foo := '' || 'goodbye'      # 'goodbye'
+bar := 'hello' || 'goodbye' # 'hello'
+```
+
 #### Joining Paths
 
 The `/` operator can be used to join two strings with a slash:
@@ -1497,8 +1532,8 @@ Done!
 
 ### Functions
 
-`just` provides a few built-in functions that might be useful when writing
-recipes.
+`just` provides many built-in functions for use in expressions, including
+recipe body `{{…}}` substitutions, assignments, and default parameter values.
 
 All functions ending in `_directory` can be abbreviated to `_dir`. So
 `home_directory()` can also be written as `home_dir()`. In addition,
@@ -2059,6 +2094,10 @@ See the [Strings](#strings) section for details on unindenting.
 Backticks may not start with `#!`. This syntax is reserved for a future
 upgrade.
 
+The [`shell(…)` function](#external-commands) provides a more general mechanism
+to invoke external commands, including the ability to execute the contents of a
+variable as a command, and to pass arguments to a command.
+
 ### Conditional Expressions
 
 `if`/`else` expressions evaluate different branches depending on if two
@@ -2363,8 +2402,8 @@ Testing server:unit…
 ./test --tests unit server
 ```
 
-Default values may be arbitrary expressions, but concatenations or path joins
-must be parenthesized:
+Default values may be arbitrary expressions, but expressions containing the
+`+`, `&&`, `||`, or `/` operators must be parenthesized:
 
 ```just
 arch := "wasm"
@@ -2736,7 +2775,7 @@ pass a Windows-style path to the interpreter.
 Recipe lines are interpreted by the shell, not `just`, so it's not possible to
 set `just` variables in the middle of a recipe:
 
-```mf
+```justfile
 foo:
   x := "hello" # This doesn't work!
   echo {{x}}
@@ -2868,7 +2907,7 @@ means that multi-line constructs probably won't do what you want.
 
 For example, with the following `justfile`:
 
-```mf
+```justfile
 conditional:
   if true; then
     echo 'True!'
@@ -3275,7 +3314,7 @@ One `justfile` can include the contents of another using `import` statements.
 
 If you have the following `justfile`:
 
-```mf
+```justfile
 import 'foo/bar.just'
 
 a: b
@@ -3315,11 +3354,37 @@ set, variables in parent modules override variables in imports.
 
 Imports may be made optional by putting a `?` after the `import` keyword:
 
-```mf
+```just
 import? 'foo/bar.just'
 ```
 
-Missing source files for optional imports do not produce an error.
+Importing the same source file multiple times is not an error<sup>master</sup>.
+This allows importing multiple justfiles, for example `foo.just` and
+`bar.just`, which both import a third justfile containing shared recipes, for
+example `baz.just`, without the duplicate import of `baz.just` being an error:
+
+```justfile
+# justfile
+import 'foo.just'
+import 'bar.just'
+```
+
+```justfile
+# foo.just
+import 'baz.just'
+foo: baz
+```
+
+```justfile
+# bar.just
+import 'baz.just'
+bar: baz
+```
+
+```just
+# baz
+baz:
+```
 
 ### Modules<sup>1.19.0</sup>
 
@@ -3331,7 +3396,7 @@ versions, you'll need to use the `--unstable` flag, `set unstable`, or set the
 
 If you have the following `justfile`:
 
-```mf
+```justfile
 mod bar
 
 a:
@@ -3369,7 +3434,7 @@ the module file may have any capitalization.
 
 Module statements may be of the form:
 
-```mf
+```justfile
 mod foo 'PATH'
 ```
 
@@ -3393,7 +3458,7 @@ recipes.
 
 Modules may be made optional by putting a `?` after the `mod` keyword:
 
-```mf
+```just
 mod? foo
 ```
 
@@ -3403,7 +3468,7 @@ Optional modules with no source file do not conflict, so you can have multiple
 mod statements with the same name, but with different source file paths, as
 long as at most one source file exists:
 
-```mf
+```just
 mod? foo 'bar.just'
 mod? foo 'baz.just'
 ```
@@ -3411,7 +3476,7 @@ mod? foo 'baz.just'
 Modules may be given doc comments which appear in `--list`
 output<sup>1.30.0</sup>:
 
-```mf
+```justfile
 # foo is a great module!
 mod foo
 ```
@@ -3553,9 +3618,9 @@ The following command will create two files, `some` and `argument.txt`:
 $ just foo "some argument.txt"
 ```
 
-The users shell will parse `"some argument.txt"` as a single argument, but when
-`just` replaces `touch {{argument}}` with `touch some argument.txt`, the quotes
-are not preserved, and `touch` will receive two arguments.
+The user's shell will parse `"some argument.txt"` as a single argument, but
+when `just` replaces `touch {{argument}}` with `touch some argument.txt`, the
+quotes are not preserved, and `touch` will receive two arguments.
 
 There are a few ways to avoid this: quoting, positional arguments, and exported
 arguments.
@@ -3880,6 +3945,38 @@ fetch:
 Given the above `justfile`, after running `just fetch`, the recipes in
 `foo.just` will be available.
 
+### Printing Complex Strings
+
+`echo` can be used to print strings, but because it processes escape sequences,
+like `\n`, and different implementations of `echo` recognize different escape
+sequences, using `printf` is often a better choice.
+
+`printf` takes a C-style format string and any number of arguments, which are
+interpolated into the format string.
+
+This can be combined with indented, triple quoted strings to emulate shell
+heredocs.
+
+Substitution complex strings into recipe bodies with `{…}` can also lead to
+trouble as it may be split by the shell into multiple arguments depending on
+the presence of whitespace and quotes. Exporting complex strings as environment
+variables and referring to them with `"$NAME"`, note the double quotes, can
+also help.
+
+Putting all this together, to print a string verbatim to standard output, with
+all its various escape sequences and quotes undisturbed:
+
+```just
+export FOO := '''
+  a complicated string with
+  some dis\tur\bi\ng escape sequences
+  and "quotes" of 'different' kinds
+'''
+
+bar:
+  printf %s "$FOO"
+```
+
 ### Alternatives and Prior Art
 
 There is no shortage of command runners! Some more or less similar alternatives

README.中文.md

@@ -144,13 +144,13 @@ list:
   <tr>
     <td><a href="https://nixos.org/download.html#download-nix">Various</a></td>
     <td><a href="https://nixos.org/nix/">Nix</a></td>
-    <td><a href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix">just</a></td>
+    <td><a href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ju/just/package.nix">just</a></td>
     <td><code>nix-env -iA nixpkgs.just</code></td>
   </tr>
   <tr>
     <td><a href="https://nixos.org/nixos/">NixOS</a></td>
     <td><a href="https://nixos.org/nix/">Nix</a></td>
-    <td><a href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix">just</a></td>
+    <td><a href="https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/ju/just/package.nix">just</a></td>
     <td><code>nix-env -iA nixos.just</code></td>
   </tr>
   <tr>
@@ -2303,6 +2303,19 @@ foo $argument:
 
 - [`watchexec`](https://github.com/mattgreen/watchexec) — 一个简单的工具，它监控一个路径，并在检测到修改时运行一个命令。
 
+### 并行运行任务
+
+GNU parallel 可以用来同时运行多个任务：
+
+```just
+parallel:
+  #!/usr/bin/env -S parallel --shebang --ungroup --jobs {{ num_cpus() }}
+  echo task 1 start; sleep 3; echo task 1 done
+  echo task 2 start; sleep 3; echo task 2 done
+  echo task 3 start; sleep 3; echo task 3 done
+  echo task 4 start; sleep 3; echo task 4 done
+```
+
 ### Shell 别名
 
 为了快速运行命令, 可以把 `alias j=just` 放在你的 Shell 配置文件中。

justfile

@@ -12,7 +12,7 @@ export JUST_LOG := log
 watch +args='test':
   cargo watch --clear --exec '{{ args }}'
 
-[group: 'test']
+[group('test')]
 test:
   cargo test --all
 
@@ -34,6 +34,7 @@ run:
 filter PATTERN:
   cargo test {{PATTERN}}
 
+[group: 'misc']
 [group: 'misc']
 build:
   cargo build

src/analyzer.rs

@@ -35,12 +35,16 @@ impl<'run, 'src> Analyzer<'run, 'src> {
     root: &Path,
   ) -> CompileResult<'src, Justfile<'src>> {
     let mut definitions = HashMap::new();
+    let mut imports = HashSet::new();
+    let mut unstable_features = BTreeSet::new();
 
     let mut stack = Vec::new();
     let ast = asts.get(root).unwrap();
     stack.push(ast);
 
     while let Some(ast) = stack.pop() {
+      unstable_features.extend(&ast.unstable_features);
+
       for item in &ast.items {
         match item {
           Item::Alias(alias) => {
@@ -54,7 +58,9 @@ impl<'run, 'src> Analyzer<'run, 'src> {
           Item::Comment(_) => (),
           Item::Import { absolute, .. } => {
             if let Some(absolute) = absolute {
-              stack.push(asts.get(absolute).unwrap());
+              if imports.insert(absolute) {
+                stack.push(asts.get(absolute).unwrap());
+              }
             }
           }
           Item::Module {
@@ -163,8 +169,6 @@ impl<'run, 'src> Analyzer<'run, 'src> {
       aliases.insert(Self::resolve_alias(&recipes, alias)?);
     }
 
-    let mut unstable_features = BTreeSet::new();
-
     for recipe in recipes.values() {
       for attribute in &recipe.attributes {
         if let Attribute::Script(_) = attribute {

src/assignment_resolver.rs

@@ -31,7 +31,29 @@ impl<'src: 'run, 'run> AssignmentResolver<'src, 'run> {
     self.stack.push(name);
 
     if let Some(assignment) = self.assignments.get(name) {
-      self.resolve_expression(&assignment.value)?;
+      for variable in assignment.value.variables() {
+        let name = variable.lexeme();
+
+        if self.evaluated.contains(name) || constants().contains_key(name) {
+          continue;
+        }
+
+        if self.stack.contains(&name) {
+          self.stack.push(name);
+          return Err(
+            self.assignments[name]
+              .name
+              .error(CircularVariableDependency {
+                variable: name,
+                circle: self.stack.clone(),
+              }),
+          );
+        } else if self.assignments.contains_key(name) {
+          self.resolve_assignment(name)?;
+        } else {
+          return Err(variable.error(UndefinedVariable { variable: name }));
+        }
+      }
       self.evaluated.insert(name);
     } else {
       let message = format!("attempted to resolve unknown assignment `{name}`");
@@ -51,112 +73,6 @@ impl<'src: 'run, 'run> AssignmentResolver<'src, 'run> {
 
     Ok(())
   }
-
-  fn resolve_expression(&mut self, expression: &Expression<'src>) -> CompileResult<'src> {
-    match expression {
-      Expression::Assert {
-        condition: Condition {
-          lhs,
-          rhs,
-          operator: _,
-        },
-        error,
-      } => {
-        self.resolve_expression(lhs)?;
-        self.resolve_expression(rhs)?;
-        self.resolve_expression(error)
-      }
-      Expression::Call { thunk } => match thunk {
-        Thunk::Nullary { .. } => Ok(()),
-        Thunk::Unary { arg, .. } => self.resolve_expression(arg),
-        Thunk::UnaryOpt { args: (a, b), .. } => {
-          self.resolve_expression(a)?;
-          if let Some(b) = b.as_ref() {
-            self.resolve_expression(b)?;
-          }
-          Ok(())
-        }
-        Thunk::UnaryPlus {
-          args: (a, rest), ..
-        } => {
-          self.resolve_expression(a)?;
-          for arg in rest {
-            self.resolve_expression(arg)?;
-          }
-          Ok(())
-        }
-        Thunk::Binary { args: [a, b], .. } => {
-          self.resolve_expression(a)?;
-          self.resolve_expression(b)
-        }
-        Thunk::BinaryPlus {
-          args: ([a, b], rest),
-          ..
-        } => {
-          self.resolve_expression(a)?;
-          self.resolve_expression(b)?;
-          for arg in rest {
-            self.resolve_expression(arg)?;
-          }
-          Ok(())
-        }
-        Thunk::Ternary {
-          args: [a, b, c], ..
-        } => {
-          self.resolve_expression(a)?;
-          self.resolve_expression(b)?;
-          self.resolve_expression(c)
-        }
-      },
-      Expression::Concatenation { lhs, rhs } => {
-        self.resolve_expression(lhs)?;
-        self.resolve_expression(rhs)
-      }
-      Expression::Conditional {
-        condition: Condition {
-          lhs,
-          rhs,
-          operator: _,
-        },
-        then,
-        otherwise,
-        ..
-      } => {
-        self.resolve_expression(lhs)?;
-        self.resolve_expression(rhs)?;
-        self.resolve_expression(then)?;
-        self.resolve_expression(otherwise)
-      }
-      Expression::Group { contents } => self.resolve_expression(contents),
-      Expression::Join { lhs, rhs } => {
-        if let Some(lhs) = lhs {
-          self.resolve_expression(lhs)?;
-        }
-        self.resolve_expression(rhs)
-      }
-      Expression::StringLiteral { .. } | Expression::Backtick { .. } => Ok(()),
-      Expression::Variable { name } => {
-        let variable = name.lexeme();
-        if self.evaluated.contains(variable) || constants().contains_key(variable) {
-          Ok(())
-        } else if self.stack.contains(&variable) {
-          self.stack.push(variable);
-          Err(
-            self.assignments[variable]
-              .name
-              .error(CircularVariableDependency {
-                variable,
-                circle: self.stack.clone(),
-              }),
-          )
-        } else if self.assignments.contains_key(variable) {
-          self.resolve_assignment(variable)
-        } else {
-          Err(name.token.error(UndefinedVariable { variable }))
-        }
-      }
-    }
-  }
 }
 
 #[cfg(test)]

src/ast.rs

@@ -6,6 +6,7 @@ use super::*;
 #[derive(Debug, Clone)]
 pub(crate) struct Ast<'src> {
   pub(crate) items: Vec<Item<'src>>,
+  pub(crate) unstable_features: BTreeSet<UnstableFeature>,
   pub(crate) warnings: Vec<Warning>,
   pub(crate) working_directory: PathBuf,
 }

src/binding.rs

@@ -3,6 +3,8 @@ use super::*;
 /// A binding of `name` to `value`
 #[derive(Debug, Clone, PartialEq, Serialize)]
 pub(crate) struct Binding<'src, V = String> {
+  #[serde(skip)]
+  pub(crate) constant: bool,
   pub(crate) export: bool,
   #[serde(skip)]
   pub(crate) file_depth: u32,

src/command_ext.rs

@@ -39,7 +39,7 @@ impl CommandExt for Command {
     }
 
     for binding in scope.bindings() {
-      if settings.export || binding.export {
+      if binding.export || (settings.export && !binding.constant) {
         self.env(binding.name.lexeme(), &binding.value);
       }
     }

src/compile_error.rs

@@ -19,6 +19,114 @@ impl<'src> CompileError<'src> {
   }
 }
 
+pub(crate) fn render_compile_error(error: &CompileError) {
+  use ariadne::{Label, Report, ReportKind, Source};
+
+  let token = error.token;
+  let source = Source::from(token.src);
+
+  let start = token.offset;
+  let end = token.offset + token.length;
+
+  let path = format!("{}", token.path.display());
+  let label = Label::new((&path, start..end));
+
+  let report = Report::build(ReportKind::Error, &path, start);
+
+  let report = match &*error.kind {
+    CompileErrorKind::AttributeArgumentCountMismatch {
+      attribute,
+      found,
+      min,
+      max,
+    } => {
+      let label_msg = format!("Found {found} {}", Count("argument", *found));
+
+      let note = if min == max {
+        format!("`{attribute}` takes {min} {}", Count("argument", *min))
+      } else {
+        format!("`{attribute}` takes between {min} and {max} arguments")
+      };
+
+      report
+        .with_code("E01")
+        .with_message("Attribute argument count mismatch")
+        .with_label(label.with_message(label_msg))
+        .with_note(note)
+        .finish()
+    }
+    /*
+    CompileErrorKind::BacktickShebang => todo!(),
+    CompileErrorKind::CircularRecipeDependency { recipe, circle } => todo!(),
+    CompileErrorKind::CircularVariableDependency { variable, circle } => todo!(),
+    CompileErrorKind::DependencyArgumentCountMismatch { dependency, found, min, max } => todo!(),
+    CompileErrorKind::Redefinition { first, first_type, name, second_type } => todo!(),
+    */
+    CompileErrorKind::DuplicateAttribute { attribute, first } => {
+      let original_label = source
+        .line(*first)
+        .map(|line| Label::new((&path, line.span())).with_message("original"));
+
+      let mut report = report
+        .with_code("E02")
+        .with_message(format!("Duplicate attribute `{attribute}`"));
+      if let Some(original) = original_label {
+        report = report.with_label(original);
+      }
+      report.with_label(label.with_message("duplicate")).finish()
+    }
+    _ => {
+      let message = format!("{error}");
+      report.with_message(message).with_label(label).finish()
+    } /*
+      CompileErrorKind::DuplicateParameter { recipe, parameter } => todo!(),
+      CompileErrorKind::DuplicateSet { setting, first } => todo!(),
+      CompileErrorKind::DuplicateVariable { variable } => todo!(),
+      CompileErrorKind::DuplicateUnexport { variable } => todo!(),
+      CompileErrorKind::ExpectedKeyword { expected, found } => todo!(),
+      CompileErrorKind::ExportUnexported { variable } => todo!(),
+      CompileErrorKind::ExtraLeadingWhitespace => todo!(),
+      CompileErrorKind::ExtraneousAttributes { count } => todo!(),
+      CompileErrorKind::FunctionArgumentCountMismatch { function, found, expected } => todo!(),
+      CompileErrorKind::Include => todo!(),
+      CompileErrorKind::InconsistentLeadingWhitespace { expected, found } => todo!(),
+      CompileErrorKind::Internal { message } => todo!(),
+      CompileErrorKind::InvalidAttribute { item_kind, item_name, attribute } => todo!(),
+      CompileErrorKind::InvalidEscapeSequence { character } => todo!(),
+      CompileErrorKind::MismatchedClosingDelimiter { close, open, open_line } => todo!(),
+      CompileErrorKind::MixedLeadingWhitespace { whitespace } => todo!(),
+      CompileErrorKind::ParameterFollowsVariadicParameter { parameter } => todo!(),
+      CompileErrorKind::ParsingRecursionDepthExceeded => todo!(),
+      CompileErrorKind::RequiredParameterFollowsDefaultParameter { parameter } => todo!(),
+      CompileErrorKind::ShebangAndScriptAttribute { recipe } => todo!(),
+      CompileErrorKind::ShellExpansion { err } => todo!(),
+      CompileErrorKind::UndefinedVariable { variable } => todo!(),
+      CompileErrorKind::UnexpectedCharacter { expected } => todo!(),
+      CompileErrorKind::UnexpectedClosingDelimiter { close } => todo!(),
+      CompileErrorKind::UnexpectedEndOfToken { expected } => todo!(),
+      CompileErrorKind::UnexpectedToken { expected, found } => todo!(),
+      CompileErrorKind::UnicodeEscapeCharacter { character } => todo!(),
+      CompileErrorKind::UnicodeEscapeDelimiter { character } => todo!(),
+      CompileErrorKind::UnicodeEscapeEmpty => todo!(),
+      CompileErrorKind::UnicodeEscapeLength { hex } => todo!(),
+      CompileErrorKind::UnicodeEscapeRange { hex } => todo!(),
+      CompileErrorKind::UnicodeEscapeUnterminated => todo!(),
+      CompileErrorKind::UnknownAliasTarget { alias, target } => todo!(),
+      CompileErrorKind::UnknownAttribute { attribute } => todo!(),
+      CompileErrorKind::UnknownDependency { recipe, unknown } => todo!(),
+      CompileErrorKind::UnknownFunction { function } => todo!(),
+      CompileErrorKind::UnknownSetting { setting } => todo!(),
+      CompileErrorKind::UnknownStartOfToken => todo!(),
+      CompileErrorKind::UnpairedCarriageReturn => todo!(),
+      CompileErrorKind::UnterminatedBacktick => todo!(),
+      CompileErrorKind::UnterminatedInterpolation => todo!(),
+      CompileErrorKind::UnterminatedString => todo!(),
+      */
+  };
+
+  report.eprint((&path, source)).unwrap();
+}
+
 fn capitalize(s: &str) -> String {
   let mut chars = s.chars();
   match chars.next() {

src/compiler.rs

@@ -21,7 +21,6 @@ impl Compiler {
       let tokens = Lexer::lex(relative, src)?;
       let mut ast = Parser::parse(
         current.file_depth,
-        &current.path,
         &current.import_offsets,
         &current.namepath,
         &tokens,
@@ -214,14 +213,7 @@ impl Compiler {
   #[cfg(test)]
   pub(crate) fn test_compile(src: &str) -> CompileResult<Justfile> {
     let tokens = Lexer::test_lex(src)?;
-    let ast = Parser::parse(
-      0,
-      &PathBuf::new(),
-      &[],
-      &Namepath::default(),
-      &tokens,
-      &PathBuf::new(),
-    )?;
+    let ast = Parser::parse(0, &[], &Namepath::default(), &tokens, &PathBuf::new())?;
     let root = PathBuf::from("justfile");
     let mut asts: HashMap<PathBuf, Ast> = HashMap::new();
     asts.insert(root.clone(), ast);

src/error.rs

@@ -504,6 +504,13 @@ impl<'src> ColorDisplay for Error<'src> {
   }
 }
 
+pub(crate) fn render_error(error: &Error, color: Color) {
+  match error {
+    Error::Compile { compile_error } => compile_error::render_compile_error(compile_error),
+    _ => eprintln!("{}", error.color_display(color.stderr())),
+  }
+}
+
 fn format_cmd(binary: &OsString, arguments: &Vec<OsString>) -> String {
   iter::once(binary)
     .chain(arguments)

src/evaluator.rs

@@ -32,12 +32,14 @@ impl<'src, 'run> Evaluator<'src, 'run> {
 
     for (name, value) in overrides {
       if let Some(assignment) = module.assignments.get(name) {
-        scope.bind(
-          assignment.export,
-          assignment.name,
-          assignment.private,
-          value.clone(),
-        );
+        scope.bind(Binding {
+          constant: false,
+          export: assignment.export,
+          file_depth: 0,
+          name: assignment.name,
+          private: assignment.private,
+          value: value.clone(),
+        });
       } else {
         unknown_overrides.push(name.clone());
       }
@@ -68,12 +70,14 @@ impl<'src, 'run> Evaluator<'src, 'run> {
 
     if !self.scope.bound(name) {
       let value = self.evaluate_expression(&assignment.value)?;
-      self.scope.bind(
-        assignment.export,
-        assignment.name,
-        assignment.private,
+      self.scope.bind(Binding {
+        constant: false,
+        export: assignment.export,
+        file_depth: 0,
+        name: assignment.name,
+        private: assignment.private,
         value,
-      );
+      });
     }
 
     Ok(self.scope.value(name).unwrap())
@@ -84,24 +88,31 @@ impl<'src, 'run> Evaluator<'src, 'run> {
     expression: &Expression<'src>,
   ) -> RunResult<'src, String> {
     match expression {
-      Expression::Variable { name, .. } => {
-        let variable = name.lexeme();
-        if let Some(value) = self.scope.value(variable) {
-          Ok(value.to_owned())
-        } else if let Some(assignment) = self
-          .assignments
-          .and_then(|assignments| assignments.get(variable))
-        {
-          Ok(self.evaluate_assignment(assignment)?.to_owned())
+      Expression::And { lhs, rhs } => {
+        let lhs = self.evaluate_expression(lhs)?;
+        if lhs.is_empty() {
+          return Ok(String::new());
+        }
+        self.evaluate_expression(rhs)
+      }
+      Expression::Assert { condition, error } => {
+        if self.evaluate_condition(condition)? {
+          Ok(String::new())
         } else {
-          Err(Error::Internal {
-            message: format!("attempted to evaluate undefined variable `{variable}`"),
+          Err(Error::Assert {
+            message: self.evaluate_expression(error)?,
           })
         }
       }
+      Expression::Backtick { contents, token } => {
+        if self.context.config.dry_run {
+          Ok(format!("`{contents}`"))
+        } else {
+          Ok(self.run_backtick(contents, token)?)
+        }
+      }
       Expression::Call { thunk } => {
         use Thunk::*;
-
         let result = match thunk {
           Nullary { function, .. } => function(function::Context::new(self, thunk.name())),
           Unary { function, arg, .. } => {
@@ -118,7 +129,6 @@ impl<'src, 'run> Evaluator<'src, 'run> {
               Some(b) => Some(self.evaluate_expression(b)?),
               None => None,
             };
-
             function(function::Context::new(self, thunk.name()), &a, b.as_deref())
           }
           UnaryPlus {
@@ -175,20 +185,11 @@ impl<'src, 'run> Evaluator<'src, 'run> {
             function(function::Context::new(self, thunk.name()), &a, &b, &c)
           }
         };
-
         result.map_err(|message| Error::FunctionCall {
           function: thunk.name(),
           message,
         })
       }
-      Expression::StringLiteral { string_literal } => Ok(string_literal.cooked.clone()),
-      Expression::Backtick { contents, token } => {
-        if self.context.config.dry_run {
-          Ok(format!("`{contents}`"))
-        } else {
-          Ok(self.run_backtick(contents, token)?)
-        }
-      }
       Expression::Concatenation { lhs, rhs } => {
         Ok(self.evaluate_expression(lhs)? + &self.evaluate_expression(rhs)?)
       }
@@ -209,12 +210,26 @@ impl<'src, 'run> Evaluator<'src, 'run> {
         lhs: Some(lhs),
         rhs,
       } => Ok(self.evaluate_expression(lhs)? + "/" + &self.evaluate_expression(rhs)?),
-      Expression::Assert { condition, error } => {
-        if self.evaluate_condition(condition)? {
-          Ok(String::new())
+      Expression::Or { lhs, rhs } => {
+        let lhs = self.evaluate_expression(lhs)?;
+        if !lhs.is_empty() {
+          return Ok(lhs);
+        }
+        self.evaluate_expression(rhs)
+      }
+      Expression::StringLiteral { string_literal } => Ok(string_literal.cooked.clone()),
+      Expression::Variable { name, .. } => {
+        let variable = name.lexeme();
+        if let Some(value) = self.scope.value(variable) {
+          Ok(value.to_owned())
+        } else if let Some(assignment) = self
+          .assignments
+          .and_then(|assignments| assignments.get(variable))
+        {
+          Ok(self.evaluate_assignment(assignment)?.to_owned())
         } else {
-          Err(Error::Assert {
-            message: self.evaluate_expression(error)?,
+          Err(Error::Internal {
+            message: format!("attempted to evaluate undefined variable `{variable}`"),
           })
         }
       }
@@ -329,9 +344,14 @@ impl<'src, 'run> Evaluator<'src, 'run> {
         rest = &rest[1..];
         value
       };
-      evaluator
-        .scope
-        .bind(parameter.export, parameter.name, false, value);
+      evaluator.scope.bind(Binding {
+        constant: false,
+        export: parameter.export,
+        file_depth: 0,
+        name: parameter.name,
+        private: false,
+        value,
+      });
     }
 
     Ok((evaluator.scope, positional))

src/expression.rs

@@ -8,6 +8,11 @@ use super::*;
 /// The parser parses both values and expressions into `Expression`s.
 #[derive(PartialEq, Debug, Clone)]
 pub(crate) enum Expression<'src> {
+  /// `lhs && rhs`
+  And {
+    lhs: Box<Expression<'src>>,
+    rhs: Box<Expression<'src>>,
+  },
   /// `assert(condition, error)`
   Assert {
     condition: Condition<'src>,
@@ -38,6 +43,11 @@ pub(crate) enum Expression<'src> {
     lhs: Option<Box<Expression<'src>>>,
     rhs: Box<Expression<'src>>,
   },
+  /// `lhs || rhs`
+  Or {
+    lhs: Box<Expression<'src>>,
+    rhs: Box<Expression<'src>>,
+  },
   /// `"string_literal"` or `'string_literal'`
   StringLiteral { string_literal: StringLiteral<'src> },
   /// `variable`
@@ -53,23 +63,25 @@ impl<'src> Expression<'src> {
 impl<'src> Display for Expression<'src> {
   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
     match self {
+      Self::And { lhs, rhs } => write!(f, "{lhs} && {rhs}"),
       Self::Assert { condition, error } => write!(f, "assert({condition}, {error})"),
       Self::Backtick { token, .. } => write!(f, "{}", token.lexeme()),
-      Self::Join { lhs: None, rhs } => write!(f, "/ {rhs}"),
-      Self::Join {
-        lhs: Some(lhs),
-        rhs,
-      } => write!(f, "{lhs} / {rhs}"),
+      Self::Call { thunk } => write!(f, "{thunk}"),
       Self::Concatenation { lhs, rhs } => write!(f, "{lhs} + {rhs}"),
       Self::Conditional {
         condition,
         then,
         otherwise,
       } => write!(f, "if {condition} {{ {then} }} else {{ {otherwise} }}"),
+      Self::Group { contents } => write!(f, "({contents})"),
+      Self::Join { lhs: None, rhs } => write!(f, "/ {rhs}"),
+      Self::Join {
+        lhs: Some(lhs),
+        rhs,
+      } => write!(f, "{lhs} / {rhs}"),
+      Self::Or { lhs, rhs } => write!(f, "{lhs} || {rhs}"),
       Self::StringLiteral { string_literal } => write!(f, "{string_literal}"),
       Self::Variable { name } => write!(f, "{}", name.lexeme()),
-      Self::Call { thunk } => write!(f, "{thunk}"),
-      Self::Group { contents } => write!(f, "({contents})"),
     }
   }
 }
@@ -80,6 +92,13 @@ impl<'src> Serialize for Expression<'src> {
     S: Serializer,
   {
     match self {
+      Self::And { lhs, rhs } => {
+        let mut seq = serializer.serialize_seq(None)?;
+        seq.serialize_element("and")?;
+        seq.serialize_element(lhs)?;
+        seq.serialize_element(rhs)?;
+        seq.end()
+      }
       Self::Assert { condition, error } => {
         let mut seq: <S as Serializer>::SerializeSeq = serializer.serialize_seq(None)?;
         seq.serialize_element("assert")?;
@@ -101,13 +120,6 @@ impl<'src> Serialize for Expression<'src> {
         seq.serialize_element(rhs)?;
         seq.end()
       }
-      Self::Join { lhs, rhs } => {
-        let mut seq = serializer.serialize_seq(None)?;
-        seq.serialize_element("join")?;
-        seq.serialize_element(lhs)?;
-        seq.serialize_element(rhs)?;
-        seq.end()
-      }
       Self::Conditional {
         condition,
         then,
@@ -121,6 +133,20 @@ impl<'src> Serialize for Expression<'src> {
         seq.end()
       }
       Self::Group { contents } => contents.serialize(serializer),
+      Self::Join { lhs, rhs } => {
+        let mut seq = serializer.serialize_seq(None)?;
+        seq.serialize_element("join")?;
+        seq.serialize_element(lhs)?;
+        seq.serialize_element(rhs)?;
+        seq.end()
+      }
+      Self::Or { lhs, rhs } => {
+        let mut seq = serializer.serialize_seq(None)?;
+        seq.serialize_element("or")?;
+        seq.serialize_element(lhs)?;
+        seq.serialize_element(rhs)?;
+        seq.end()
+      }
       Self::StringLiteral { string_literal } => string_literal.serialize(serializer),
       Self::Variable { name } => {
         let mut seq = serializer.serialize_seq(None)?;

src/justfile.rs

@@ -346,7 +346,7 @@ impl<'src> Justfile<'src> {
     if !context.config.no_dependencies {
       let mut ran = Ran::default();
 
-      for Dependency { recipe, arguments } in recipe.dependencies.iter().skip(recipe.priors) {
+      for Dependency { recipe, arguments } in recipe.subsequents() {
         let mut evaluated = Vec::new();
 
         for argument in arguments {

src/lexer.rs

@@ -496,6 +496,7 @@ impl<'src> Lexer<'src> {
       ']' => self.lex_delimiter(BracketR),
       '`' | '"' | '\'' => self.lex_string(),
       '{' => self.lex_delimiter(BraceL),
+      '|' => self.lex_digraph('|', '|', BarBar),
       '}' => self.lex_delimiter(BraceR),
       _ if Self::is_identifier_start(start) => self.lex_identifier(),
       _ => {
@@ -948,6 +949,7 @@ mod tests {
       Asterisk => "*",
       At => "@",
       BangEquals => "!=",
+      BarBar => "||",
       BraceL => "{",
       BraceR => "}",
       BracketL => "[",

src/node.rs

@@ -88,6 +88,7 @@ impl<'src> Node<'src> for Assignment<'src> {
 impl<'src> Node<'src> for Expression<'src> {
   fn tree(&self) -> Tree<'src> {
     match self {
+      Self::And { lhs, rhs } => Tree::atom("&&").push(lhs.tree()).push(rhs.tree()),
       Self::Assert {
         condition: Condition { lhs, rhs, operator },
         error,
@@ -96,25 +97,10 @@ impl<'src> Node<'src> for Expression<'src> {
         .push(operator.to_string())
         .push(rhs.tree())
         .push(error.tree()),
-      Self::Concatenation { lhs, rhs } => Tree::atom("+").push(lhs.tree()).push(rhs.tree()),
-      Self::Conditional {
-        condition: Condition { lhs, rhs, operator },
-        then,
-        otherwise,
-      } => {
-        let mut tree = Tree::atom(Keyword::If.lexeme());
-        tree.push_mut(lhs.tree());
-        tree.push_mut(operator.to_string());
-        tree.push_mut(rhs.tree());
-        tree.push_mut(then.tree());
-        tree.push_mut(otherwise.tree());
-        tree
-      }
+      Self::Backtick { contents, .. } => Tree::atom("backtick").push(Tree::string(contents)),
       Self::Call { thunk } => {
         use Thunk::*;
-
         let mut tree = Tree::atom("call");
-
         match thunk {
           Nullary { name, .. } => tree.push_mut(name.lexeme()),
           Unary { name, arg, .. } => {
@@ -171,20 +157,33 @@ impl<'src> Node<'src> for Expression<'src> {
             tree.push_mut(c.tree());
           }
         }
-
         tree
       }
-      Self::Variable { name } => Tree::atom(name.lexeme()),
-      Self::StringLiteral {
-        string_literal: StringLiteral { cooked, .. },
-      } => Tree::string(cooked),
-      Self::Backtick { contents, .. } => Tree::atom("backtick").push(Tree::string(contents)),
+      Self::Concatenation { lhs, rhs } => Tree::atom("+").push(lhs.tree()).push(rhs.tree()),
+      Self::Conditional {
+        condition: Condition { lhs, rhs, operator },
+        then,
+        otherwise,
+      } => {
+        let mut tree = Tree::atom(Keyword::If.lexeme());
+        tree.push_mut(lhs.tree());
+        tree.push_mut(operator.to_string());
+        tree.push_mut(rhs.tree());
+        tree.push_mut(then.tree());
+        tree.push_mut(otherwise.tree());
+        tree
+      }
       Self::Group { contents } => Tree::List(vec![contents.tree()]),
       Self::Join { lhs: None, rhs } => Tree::atom("/").push(rhs.tree()),
       Self::Join {
         lhs: Some(lhs),
         rhs,
       } => Tree::atom("/").push(lhs.tree()).push(rhs.tree()),
+      Self::Or { lhs, rhs } => Tree::atom("||").push(lhs.tree()).push(rhs.tree()),
+      Self::StringLiteral {
+        string_literal: StringLiteral { cooked, .. },
+      } => Tree::string(cooked),
+      Self::Variable { name } => Tree::atom(name.lexeme()),
     }
   }
 }

src/parser.rs

@@ -26,12 +26,12 @@ use {super::*, TokenKind::*};
 pub(crate) struct Parser<'run, 'src> {
   expected_tokens: BTreeSet<TokenKind>,
   file_depth: u32,
-  file_path: &'run Path,
   import_offsets: Vec<usize>,
   module_namepath: &'run Namepath<'src>,
   next_token: usize,
   recursion_depth: usize,
   tokens: &'run [Token<'src>],
+  unstable_features: BTreeSet<UnstableFeature>,
   working_directory: &'run Path,
 }
 
@@ -39,7 +39,6 @@ impl<'run, 'src> Parser<'run, 'src> {
   /// Parse `tokens` into an `Ast`
   pub(crate) fn parse(
     file_depth: u32,
-    file_path: &'run Path,
     import_offsets: &[usize],
     module_namepath: &'run Namepath<'src>,
     tokens: &'run [Token<'src>],
@@ -48,12 +47,12 @@ impl<'run, 'src> Parser<'run, 'src> {
     Self {
       expected_tokens: BTreeSet::new(),
       file_depth,
-      file_path,
       import_offsets: import_offsets.to_vec(),
       module_namepath,
       next_token: 0,
       recursion_depth: 0,
       tokens,
+      unstable_features: BTreeSet::new(),
       working_directory,
     }
     .parse_ast()
@@ -445,18 +444,19 @@ impl<'run, 'src> Parser<'run, 'src> {
       }
     }
 
-    if self.next_token == self.tokens.len() {
-      Ok(Ast {
-        items,
-        warnings: Vec::new(),
-        working_directory: self.working_directory.into(),
-      })
-    } else {
-      Err(self.internal_error(format!(
+    if self.next_token != self.tokens.len() {
+      return Err(self.internal_error(format!(
         "Parse completed with {} unparsed tokens",
         self.tokens.len() - self.next_token,
-      ))?)
+      ))?);
     }
+
+    Ok(Ast {
+      items,
+      unstable_features: self.unstable_features,
+      warnings: Vec::new(),
+      working_directory: self.working_directory.into(),
+    })
   }
 
   /// Parse an alias, e.g `alias name := target`
@@ -500,11 +500,12 @@ impl<'run, 'src> Parser<'run, 'src> {
     }
 
     Ok(Assignment {
-      file_depth: self.file_depth,
+      constant: false,
       export,
+      file_depth: self.file_depth,
       name,
-      value,
       private: private || name.lexeme().starts_with('_'),
+      value,
     })
   }
 
@@ -520,26 +521,17 @@ impl<'run, 'src> Parser<'run, 'src> {
 
     self.recursion_depth += 1;
 
-    let expression = if self.accepted_keyword(Keyword::If)? {
-      self.parse_conditional()?
-    } else if self.accepted(Slash)? {
-      let lhs = None;
-      let rhs = self.parse_expression()?.into();
-      Expression::Join { lhs, rhs }
-    } else {
-      let value = self.parse_value()?;
+    let disjunct = self.parse_disjunct()?;
 
-      if self.accepted(Slash)? {
-        let lhs = Some(Box::new(value));
-        let rhs = self.parse_expression()?.into();
-        Expression::Join { lhs, rhs }
-      } else if self.accepted(Plus)? {
-        let lhs = value.into();
-        let rhs = self.parse_expression()?.into();
-        Expression::Concatenation { lhs, rhs }
-      } else {
-        value
-      }
+    let expression = if self.accepted(BarBar)? {
+      self
+        .unstable_features
+        .insert(UnstableFeature::LogicalOperators);
+      let lhs = disjunct.into();
+      let rhs = self.parse_expression()?.into();
+      Expression::Or { lhs, rhs }
+    } else {
+      disjunct
     };
 
     self.recursion_depth -= 1;
@@ -547,6 +539,47 @@ impl<'run, 'src> Parser<'run, 'src> {
     Ok(expression)
   }
 
+  fn parse_disjunct(&mut self) -> CompileResult<'src, Expression<'src>> {
+    let conjunct = self.parse_conjunct()?;
+
+    let disjunct = if self.accepted(AmpersandAmpersand)? {
+      self
+        .unstable_features
+        .insert(UnstableFeature::LogicalOperators);
+      let lhs = conjunct.into();
+      let rhs = self.parse_disjunct()?.into();
+      Expression::And { lhs, rhs }
+    } else {
+      conjunct
+    };
+
+    Ok(disjunct)
+  }
+
+  fn parse_conjunct(&mut self) -> CompileResult<'src, Expression<'src>> {
+    if self.accepted_keyword(Keyword::If)? {
+      self.parse_conditional()
+    } else if self.accepted(Slash)? {
+      let lhs = None;
+      let rhs = self.parse_conjunct()?.into();
+      Ok(Expression::Join { lhs, rhs })
+    } else {
+      let value = self.parse_value()?;
+
+      if self.accepted(Slash)? {
+        let lhs = Some(Box::new(value));
+        let rhs = self.parse_conjunct()?.into();
+        Ok(Expression::Join { lhs, rhs })
+      } else if self.accepted(Plus)? {
+        let lhs = value.into();
+        let rhs = self.parse_conjunct()?.into();
+        Ok(Expression::Concatenation { lhs, rhs })
+      } else {
+        Ok(value)
+      }
+    }
+  }
+
   /// Parse a conditional, e.g. `if a == b { "foo" } else { "bar" }`
   fn parse_conditional(&mut self) -> CompileResult<'src, Expression<'src>> {
     let condition = self.parse_condition()?;
@@ -910,7 +943,6 @@ impl<'run, 'src> Parser<'run, 'src> {
       dependencies,
       doc,
       file_depth: self.file_depth,
-      file_path: self.file_path.into(),
       import_offsets: self.import_offsets.clone(),
       name,
       namepath: self.module_namepath.join(name),
@@ -1162,15 +1194,8 @@ mod tests {
   fn test(text: &str, want: Tree) {
     let unindented = unindent(text);
     let tokens = Lexer::test_lex(&unindented).expect("lexing failed");
-    let justfile = Parser::parse(
-      0,
-      &PathBuf::new(),
-      &[],
-      &Namepath::default(),
-      &tokens,
-      &PathBuf::new(),
-    )
-    .expect("parsing failed");
+    let justfile = Parser::parse(0, &[], &Namepath::default(), &tokens, &PathBuf::new())
+      .expect("parsing failed");
     let have = justfile.tree();
     if have != want {
       println!("parsed text: {unindented}");
@@ -1208,14 +1233,7 @@ mod tests {
   ) {
     let tokens = Lexer::test_lex(src).expect("Lexing failed in parse test...");
 
-    match Parser::parse(
-      0,
-      &PathBuf::new(),
-      &[],
-      &Namepath::default(),
-      &tokens,
-      &PathBuf::new(),
-    ) {
+    match Parser::parse(0, &[], &Namepath::default(), &tokens, &PathBuf::new()) {
       Ok(_) => panic!("Parsing unexpectedly succeeded"),
       Err(have) => {
         let want = CompileError {

src/recipe.rs

@@ -26,8 +26,6 @@ pub(crate) struct Recipe<'src, D = Dependency<'src>> {
   #[serde(skip)]
   pub(crate) file_depth: u32,
   #[serde(skip)]
-  pub(crate) file_path: PathBuf,
-  #[serde(skip)]
   pub(crate) import_offsets: Vec<usize>,
   pub(crate) name: Name<'src>,
   pub(crate) namepath: Namepath<'src>,
@@ -469,6 +467,10 @@ impl<'src, D> Recipe<'src, D> {
     }
     self.doc
   }
+
+  pub(crate) fn subsequents(&self) -> impl Iterator<Item = &D> {
+    self.dependencies.iter().skip(self.priors)
+  }
 }
 
 impl<'src, D: Display> ColorDisplay for Recipe<'src, D> {

src/run.rs

@@ -29,7 +29,7 @@ pub fn run(args: impl Iterator<Item = impl Into<OsString> + Clone>) -> Result<()
     })
     .map_err(|error| {
       if !verbosity.quiet() && error.print_message() {
-        eprintln!("{}", error.color_display(color.stderr()));
+        crate::error::render_error(&error, color);
       }
       error.code().unwrap_or(EXIT_FAILURE)
     })

src/scope.rs

@@ -21,9 +21,11 @@ impl<'src, 'run> Scope<'src, 'run> {
     };
 
     for (key, value) in constants() {
-      root.bind(
-        false,
-        Name {
+      root.bind(Binding {
+        constant: true,
+        export: false,
+        file_depth: 0,
+        name: Name {
           token: Token {
             column: 0,
             kind: TokenKind::Identifier,
@@ -34,22 +36,16 @@ impl<'src, 'run> Scope<'src, 'run> {
             src: key,
           },
         },
-        false,
-        (*value).into(),
-      );
+        private: false,
+        value: (*value).into(),
+      });
     }
 
     root
   }
 
-  pub(crate) fn bind(&mut self, export: bool, name: Name<'src>, private: bool, value: String) {
-    self.bindings.insert(Binding {
-      export,
-      file_depth: 0,
-      name,
-      private,
-      value,
-    });
+  pub(crate) fn bind(&mut self, binding: Binding<'src>) {
+    self.bindings.insert(binding);
   }
 
   pub(crate) fn bound(&self, name: &str) -> bool {

src/summary.rs

@@ -183,6 +183,10 @@ impl Assignment {
 
 #[derive(Eq, PartialEq, Hash, Ord, PartialOrd, Debug, Clone)]
 pub enum Expression {
+  And {
+    lhs: Box<Expression>,
+    rhs: Box<Expression>,
+  },
   Assert {
     condition: Condition,
     error: Box<Expression>,
@@ -209,6 +213,10 @@ pub enum Expression {
     lhs: Option<Box<Expression>>,
     rhs: Box<Expression>,
   },
+  Or {
+    lhs: Box<Expression>,
+    rhs: Box<Expression>,
+  },
   String {
     text: String,
   },
@@ -221,6 +229,10 @@ impl Expression {
   fn new(expression: &full::Expression) -> Self {
     use full::Expression::*;
     match expression {
+      And { lhs, rhs } => Self::And {
+        lhs: Self::new(lhs).into(),
+        rhs: Self::new(rhs).into(),
+      },
       Assert {
         condition: full::Condition { lhs, rhs, operator },
         error,
@@ -250,11 +262,9 @@ impl Expression {
           ..
         } => {
           let mut arguments = Vec::new();
-
           if let Some(b) = opt_b.as_ref() {
             arguments.push(Self::new(b));
           }
-
           arguments.push(Self::new(a));
           Self::Call {
             name: name.lexeme().to_owned(),
@@ -308,10 +318,6 @@ impl Expression {
         lhs: Self::new(lhs).into(),
         rhs: Self::new(rhs).into(),
       },
-      Join { lhs, rhs } => Self::Join {
-        lhs: lhs.as_ref().map(|lhs| Self::new(lhs).into()),
-        rhs: Self::new(rhs).into(),
-      },
       Conditional {
         condition: full::Condition { lhs, rhs, operator },
         otherwise,
@@ -323,13 +329,21 @@ impl Expression {
         rhs: Self::new(rhs).into(),
         then: Self::new(then).into(),
       },
+      Group { contents } => Self::new(contents),
+      Join { lhs, rhs } => Self::Join {
+        lhs: lhs.as_ref().map(|lhs| Self::new(lhs).into()),
+        rhs: Self::new(rhs).into(),
+      },
+      Or { lhs, rhs } => Self::Or {
+        lhs: Self::new(lhs).into(),
+        rhs: Self::new(rhs).into(),
+      },
       StringLiteral { string_literal } => Self::String {
         text: string_literal.cooked.clone(),
       },
       Variable { name, .. } => Self::Variable {
         name: name.lexeme().to_owned(),
       },
-      Group { contents } => Self::new(contents),
     }
   }
 }

src/testing.rs

@@ -59,15 +59,8 @@ pub(crate) fn analysis_error(
 ) {
   let tokens = Lexer::test_lex(src).expect("Lexing failed in parse test...");
 
-  let ast = Parser::parse(
-    0,
-    &PathBuf::new(),
-    &[],
-    &Namepath::default(),
-    &tokens,
-    &PathBuf::new(),
-  )
-  .expect("Parsing failed in analysis test...");
+  let ast = Parser::parse(0, &[], &Namepath::default(), &tokens, &PathBuf::new())
+    .expect("Parsing failed in analysis test...");
 
   let root = PathBuf::from("justfile");
   let mut asts: HashMap<PathBuf, Ast> = HashMap::new();

src/token_kind.rs

@@ -7,6 +7,7 @@ pub(crate) enum TokenKind {
   At,
   Backtick,
   BangEquals,
+  BarBar,
   BraceL,
   BraceR,
   BracketL,
@@ -50,6 +51,7 @@ impl Display for TokenKind {
         At => "'@'",
         Backtick => "backtick",
         BangEquals => "'!='",
+        BarBar => "'||'",
         BraceL => "'{'",
         BraceR => "'}'",
         BracketL => "'['",

src/unresolved_recipe.rs

@@ -50,7 +50,6 @@ impl<'src> UnresolvedRecipe<'src> {
       dependencies,
       doc: self.doc,
       file_depth: self.file_depth,
-      file_path: self.file_path,
       import_offsets: self.import_offsets,
       name: self.name,
       namepath: self.namepath,

src/unstable_feature.rs

@@ -3,6 +3,7 @@ use super::*;
 #[derive(Copy, Clone, Debug, PartialEq, Ord, Eq, PartialOrd)]
 pub(crate) enum UnstableFeature {
   FormatSubcommand,
+  LogicalOperators,
   ScriptAttribute,
   ScriptInterpreterSetting,
 }
@@ -11,6 +12,10 @@ impl Display for UnstableFeature {
   fn fmt(&self, f: &mut Formatter) -> fmt::Result {
     match self {
       Self::FormatSubcommand => write!(f, "The `--fmt` command is currently unstable."),
+      Self::LogicalOperators => write!(
+        f,
+        "The logical operators `&&` and `||` are currently unstable."
+      ),
       Self::ScriptAttribute => write!(f, "The `[script]` attribute is currently unstable."),
       Self::ScriptInterpreterSetting => {
         write!(f, "The `script-interpreter` setting is currently unstable.")

src/variables.rs

@@ -16,7 +16,24 @@ impl<'expression, 'src> Iterator for Variables<'expression, 'src> {
   fn next(&mut self) -> Option<Token<'src>> {
     loop {
       match self.stack.pop()? {
-        Expression::StringLiteral { .. } | Expression::Backtick { .. } => {}
+        Expression::And { lhs, rhs } | Expression::Or { lhs, rhs } => {
+          self.stack.push(lhs);
+          self.stack.push(rhs);
+        }
+        Expression::Assert {
+          condition:
+            Condition {
+              lhs,
+              rhs,
+              operator: _,
+            },
+          error,
+        } => {
+          self.stack.push(error);
+          self.stack.push(rhs);
+          self.stack.push(lhs);
+        }
+        Expression::Backtick { .. } | Expression::StringLiteral { .. } => {}
         Expression::Call { thunk } => match thunk {
           Thunk::Nullary { .. } => {}
           Thunk::Unary { arg, .. } => self.stack.push(arg),
@@ -56,6 +73,10 @@ impl<'expression, 'src> Iterator for Variables<'expression, 'src> {
             }
           }
         },
+        Expression::Concatenation { lhs, rhs } => {
+          self.stack.push(rhs);
+          self.stack.push(lhs);
+        }
         Expression::Conditional {
           condition:
             Condition {
@@ -71,10 +92,8 @@ impl<'expression, 'src> Iterator for Variables<'expression, 'src> {
           self.stack.push(rhs);
           self.stack.push(lhs);
         }
-        Expression::Variable { name, .. } => return Some(name.token),
-        Expression::Concatenation { lhs, rhs } => {
-          self.stack.push(rhs);
-          self.stack.push(lhs);
+        Expression::Group { contents } => {
+          self.stack.push(contents);
         }
         Expression::Join { lhs, rhs } => {
           self.stack.push(rhs);
@@ -82,22 +101,7 @@ impl<'expression, 'src> Iterator for Variables<'expression, 'src> {
             self.stack.push(lhs);
           }
         }
-        Expression::Group { contents } => {
-          self.stack.push(contents);
-        }
-        Expression::Assert {
-          condition:
-            Condition {
-              lhs,
-              rhs,
-              operator: _,
-            },
-          error,
-        } => {
-          self.stack.push(error);
-          self.stack.push(rhs);
-          self.stack.push(lhs);
-        }
+        Expression::Variable { name, .. } => return Some(name.token),
       }
     }
   }

tests/assert_success.rs

@@ -1,3 +1,4 @@
+#[track_caller]
 pub(crate) fn assert_success(output: &std::process::Output) {
   if !output.status.success() {
     eprintln!("stderr: {}", String::from_utf8_lossy(&output.stderr));

tests/conditional.rs

@@ -136,7 +136,7 @@ test! {
   ",
   stdout: "",
   stderr: "
-    error: Expected '!=', '==', '=~', '+', or '/', but found identifier
+    error: Expected '&&', '!=', '||', '==', '=~', '+', or '/', but found identifier
      ——▶ justfile:1:12
       │
     1 │ a := if '' a '' { '' } else { b }

tests/constants.rs

@@ -43,3 +43,19 @@ fn constants_can_be_redefined() {
     .stdout("foo")
     .run();
 }
+
+#[test]
+fn constants_are_not_exported() {
+  Test::new()
+    .justfile(
+      "
+        set export
+
+        foo:
+          echo $HEXUPPER
+      ",
+    )
+    .stderr_regex(".*HEXUPPER: unbound variable.*")
+    .status(127)
+    .run();
+}

tests/ignore_comments.rs

@@ -125,7 +125,7 @@ fn comments_still_must_be_parsable_when_ignored() {
     )
     .stderr(
       "
-        error: Expected '}}', '(', '+', or '/', but found identifier
+        error: Expected '&&', '||', '}}', '(', '+', or '/', but found identifier
          ——▶ justfile:4:12
           │
         4 │   # {{ foo bar }}

tests/imports.rs

@@ -360,3 +360,51 @@ fn reused_import_are_allowed() {
     })
     .run();
 }
+
+#[test]
+fn multiply_imported_items_do_not_conflict() {
+  Test::new()
+    .justfile(
+      "
+      import 'a.just'
+      import 'a.just'
+      foo: bar
+    ",
+    )
+    .write(
+      "a.just",
+      "
+x := 'y'
+
+@bar:
+  echo hello
+",
+    )
+    .stdout("hello\n")
+    .run();
+}
+
+#[test]
+fn nested_multiply_imported_items_do_not_conflict() {
+  Test::new()
+    .justfile(
+      "
+      import 'a.just'
+      import 'b.just'
+      foo: bar
+    ",
+    )
+    .write("a.just", "import 'c.just'")
+    .write("b.just", "import 'c.just'")
+    .write(
+      "c.just",
+      "
+x := 'y'
+
+@bar:
+  echo hello
+",
+    )
+    .stdout("hello\n")
+    .run();
+}

tests/lib.rs

@@ -73,6 +73,7 @@ mod invocation_directory;
 mod json;
 mod line_prefixes;
 mod list;
+mod logical_operators;
 mod man;
 mod misc;
 mod modules;

tests/logical_operators.rs

@@ -0,0 +1,83 @@
+use super::*;
+
+#[track_caller]
+fn evaluate(expression: &str, expected: &str) {
+  Test::new()
+    .justfile(format!("x := {expression}"))
+    .env("JUST_UNSTABLE", "1")
+    .args(["--evaluate", "x"])
+    .stdout(expected)
+    .run();
+}
+
+#[test]
+fn logical_operators_are_unstable() {
+  Test::new()
+    .justfile("x := 'foo' && 'bar'")
+    .args(["--evaluate", "x"])
+    .stderr_regex(r"error: The logical operators `&&` and `\|\|` are currently unstable. .*")
+    .status(EXIT_FAILURE)
+    .run();
+
+  Test::new()
+    .justfile("x := 'foo' || 'bar'")
+    .args(["--evaluate", "x"])
+    .stderr_regex(r"error: The logical operators `&&` and `\|\|` are currently unstable. .*")
+    .status(EXIT_FAILURE)
+    .run();
+}
+
+#[test]
+fn and_returns_empty_string_if_lhs_is_empty() {
+  evaluate("'' && 'hello'", "");
+}
+
+#[test]
+fn and_returns_rhs_if_lhs_is_non_empty() {
+  evaluate("'hello' && 'goodbye'", "goodbye");
+}
+
+#[test]
+fn and_has_lower_precedence_than_plus() {
+  evaluate("'' && 'goodbye' + 'foo'", "");
+
+  evaluate("'foo' + 'hello' && 'goodbye'", "goodbye");
+
+  evaluate("'foo' + '' && 'goodbye'", "goodbye");
+
+  evaluate("'foo' + 'hello' && 'goodbye' + 'bar'", "goodbyebar");
+}
+
+#[test]
+fn or_returns_rhs_if_lhs_is_empty() {
+  evaluate("'' || 'hello'", "hello");
+}
+
+#[test]
+fn or_returns_lhs_if_lhs_is_non_empty() {
+  evaluate("'hello' || 'goodbye'", "hello");
+}
+
+#[test]
+fn or_has_lower_precedence_than_plus() {
+  evaluate("'' || 'goodbye' + 'foo'", "goodbyefoo");
+
+  evaluate("'foo' + 'hello' || 'goodbye'", "foohello");
+
+  evaluate("'foo' + '' || 'goodbye'", "foo");
+
+  evaluate("'foo' + 'hello' || 'goodbye' + 'bar'", "foohello");
+}
+
+#[test]
+fn and_has_higher_precedence_than_or() {
+  evaluate("('' && 'foo') || 'bar'", "bar");
+  evaluate("'' && 'foo' || 'bar'", "bar");
+  evaluate("'a' && 'b' || 'c'", "b");
+}
+
+#[test]
+fn nesting() {
+  evaluate("'' || '' || '' || '' || 'foo'", "foo");
+  evaluate("'foo' && 'foo' && 'foo' && 'foo' && 'bar'", "bar");
+}

tests/shell_expansion.rs

@@ -25,7 +25,7 @@ fn shell_expanded_strings_must_not_have_whitespace() {
     .status(1)
     .stderr(
       "
-        error: Expected comment, end of file, end of line, '(', '+', or '/', but found string
+        error: Expected '&&', '||', comment, end of file, end of line, '(', '+', or '/', but found string
          ——▶ justfile:1:8
           │
         1 │ x := x '$JUST_TEST_VARIABLE'

tests/test.rs

@@ -1,4 +1,7 @@
-use {super::*, pretty_assertions::assert_eq};
+use {
+  super::*,
+  pretty_assertions::{assert_eq, StrComparison},
+};
 
 macro_rules! test {
   {
@@ -205,6 +208,14 @@ impl Test {
       equal
     }
 
+    fn compare_string(name: &str, have: &str, want: &str) -> bool {
+      let equal = have == want;
+      if !equal {
+        eprintln!("Bad {name}: {}", StrComparison::new(&have, &want));
+      }
+      equal
+    }
+
     if let Some(justfile) = &self.justfile {
       let justfile = unindent(justfile);
       fs::write(self.justfile_path(), justfile).unwrap();
@@ -266,8 +277,8 @@ impl Test {
     }
 
     if !compare("status", output.status.code(), Some(self.status))
-      | (self.stdout_regex.is_none() && !compare("stdout", output_stdout, &stdout))
-      | (self.stderr_regex.is_none() && !compare("stderr", output_stderr, &stderr))
+      | (self.stdout_regex.is_none() && !compare_string("stdout", output_stdout, &stdout))
+      | (self.stderr_regex.is_none() && !compare_string("stderr", output_stderr, &stderr))
     {
       panic!("Output mismatch.");
     }