Merge 0c6f5e8376 into 67034cb8b4

Closes #2109 (but with a function name that is shorter and more familiar)

Cargo.lock

@@ -498,6 +498,15 @@ dependencies = [
  "cc",
 ]
 
+[[package]]
+name = "is_executable"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4a1b5bad6f9072935961dfbf1cced2f3d129963d091b6f69f007fe04e758ae2"
+dependencies = [
+ "winapi",
+]
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.1"
@@ -535,8 +544,10 @@ dependencies = [
  "dirs",
  "dotenvy",
  "edit-distance",
+ "either",
  "executable-path",
  "heck",
+ "is_executable",
  "lexiclean",
  "libc",
  "num_cpus",

Cargo.toml

@@ -30,7 +30,9 @@ derivative = "2.0.0"
 dirs = "5.0.1"
 dotenvy = "0.15"
 edit-distance = "2.0.0"
+either = "1.13.0"
 heck = "0.5.0"
+is_executable = "1.0.4"
 lexiclean = "0.0.1"
 libc = "0.2.0"
 num_cpus = "1.15.0"

README.md

@@ -1632,6 +1632,22 @@ $ just
   name `key`, returning `default` if it is not present.
 - `env(key)`<sup>1.15.0</sup> — Alias for `env_var(key)`.
 - `env(key, default)`<sup>1.15.0</sup> — Alias for `env_var_or_default(key, default)`.
+- `which(exe)`<sup>master</sup> — Retrieves the full path of `exe` according
+  to the `PATH`. Returns an empty string if no executable named `exe` exists.
+
+```just
+bash := which("bash")
+nexist := which("does-not-exist")
+
+@test:
+    echo "bash: '{{bash}}'"
+    echo "nexist: '{{nexist}}'"
+```
+
+```console
+bash: '/bin/bash'
+nexist: ''
+```
 
 #### Invocation Information
 

justfile

@@ -6,6 +6,8 @@ alias t := test
 
 log := "warn"
 
+bingus := which("bash")
+
 export JUST_LOG := log
 
 [group: 'dev']

src/function.rs

@@ -1,5 +1,6 @@
 use {
   super::*,
+  either::Either,
   heck::{
     ToKebabCase, ToLowerCamelCase, ToShoutyKebabCase, ToShoutySnakeCase, ToSnakeCase, ToTitleCase,
     ToUpperCamelCase,
@@ -110,6 +111,7 @@ pub(crate) fn get(name: &str) -> Option<Function> {
     "uppercase" => Unary(uppercase),
     "uuid" => Nullary(uuid),
     "without_extension" => Unary(without_extension),
+    "which" => Unary(which),
     _ => return None,
   };
   Some(function)
@@ -667,6 +669,61 @@ fn uuid(_context: Context) -> FunctionResult {
   Ok(uuid::Uuid::new_v4().to_string())
 }
 
+fn which(context: Context, s: &str) -> FunctionResult {
+  use is_executable::IsExecutable;
+
+  let cmd = PathBuf::from(s);
+
+  let path_var;
+  let candidates = match cmd.components().count() {
+    0 => Err("empty command string".to_string())?,
+    1 => {
+      // cmd is a regular command
+      path_var = env::var_os("PATH").ok_or("Environment variable `PATH` is not set")?;
+      Either::Left(env::split_paths(&path_var).map(|path| path.join(cmd.clone())))
+    }
+    _ => {
+      // cmd contains a path separator, treat it as a path
+      Either::Right(iter::once(cmd))
+    }
+  };
+
+  for mut candidate in candidates.into_iter() {
+    if candidate.is_relative() {
+      // This candidate is a relative path, either because the user invoked `which("./rel/path")`,
+      // or because there was a relative path in `PATH`. Resolve it to an absolute path.
+      let cwd = context
+        .evaluator
+        .context
+        .search
+        .justfile
+        .parent()
+        .ok_or_else(|| {
+          format!(
+            "Could not resolve absolute path from `{}` relative to the justfile directory. Justfile `{}` had no parent.",
+            candidate.display(),
+            context.evaluator.context.search.justfile.display()
+          )
+        })?;
+      let mut cwd = PathBuf::from(cwd);
+      cwd.push(candidate);
+      candidate = cwd;
+    }
+
+    if candidate.is_executable() {
+      return candidate.to_str().map(str::to_string).ok_or_else(|| {
+        format!(
+          "Executable path is not valid unicode: {}",
+          candidate.display()
+        )
+      });
+    }
+  }
+
+  // No viable candidates; return an empty string
+  Ok(String::new())
+}
+
 fn without_extension(_context: Context, path: &str) -> FunctionResult {
   let parent = Utf8Path::new(path)
     .parent()

tests/lib.rs

@@ -111,6 +111,7 @@ mod timestamps;
 mod undefined_variables;
 mod unexport;
 mod unstable;
+mod which_exec;
 #[cfg(windows)]
 mod windows;
 #[cfg(target_family = "windows")]

tests/which_exec.rs

@@ -0,0 +1,42 @@
+use super::*;
+
+fn make_path() -> TempDir {
+  let tmp = temptree! {
+    "hello.exe": "#!/usr/bin/env bash\necho hello\n",
+  };
+
+  #[cfg(not(windows))]
+  {
+    let exe = tmp.path().join("hello.exe");
+    let perms = std::os::unix::fs::PermissionsExt::from_mode(0o755);
+    fs::set_permissions(exe, perms).unwrap();
+  }
+
+  tmp
+}
+
+#[test]
+fn finds_executable() {
+  let tmp = make_path();
+  let mut path = env::current_dir().unwrap();
+  path.push("bin");
+  Test::new()
+    .justfile(r#"p := which("hello.exe")"#)
+    .env("PATH", tmp.path().to_str().unwrap())
+    .args(["--evaluate", "p"])
+    .stdout(format!("{}", tmp.path().join("hello.exe").display()))
+    .run();
+}
+
+#[test]
+fn prints_empty_string_for_missing_executable() {
+  let tmp = make_path();
+  let mut path = env::current_dir().unwrap();
+  path.push("bin");
+  Test::new()
+    .justfile(r#"p := which("goodbye.exe")"#)
+    .env("PATH", tmp.path().to_str().unwrap())
+    .args(["--evaluate", "p"])
+    .stdout("")
+    .run();
+}