Support importing local files in the REPL

crates/compiler/parse/src/header.rs

@@ -163,6 +163,8 @@ impl<'a> From<ModuleName<'a>> for roc_module::ident::ModuleName {
 }
 
 impl<'a> ModuleName<'a> {
+    const MODULE_SEPARATOR: char = '.';
+
     pub const fn new(name: &'a str) -> Self {
         ModuleName(name)
     }
@@ -170,6 +172,10 @@ impl<'a> ModuleName<'a> {
     pub const fn as_str(&'a self) -> &'a str {
         self.0
     }
+
+    pub fn parts(&'a self) -> impl DoubleEndedIterator<Item = &'a str> {
+        self.0.split(Self::MODULE_SEPARATOR)
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]

crates/repl_cli/src/lib.rs

@@ -9,7 +9,7 @@ use roc_repl_eval::gen::Problems;
 use roc_repl_ui::colors::{CYAN, END_COL};
 use roc_repl_ui::repl_state::{ReplAction, ReplState};
 use roc_repl_ui::{format_output, is_incomplete, CONT_PROMPT, PROMPT, SHORT_INSTRUCTIONS, TIPS};
-use roc_reporting::report::{ANSI_STYLE_CODES, DEFAULT_PALETTE};
+use roc_reporting::report::{to_file_problem_report_string, ANSI_STYLE_CODES, DEFAULT_PALETTE};
 use roc_target::Target;
 use rustyline::highlight::{Highlighter, PromptInfo};
 use rustyline::validate::{self, ValidationContext, ValidationResult, Validator};
@@ -74,6 +74,9 @@ pub fn main() -> i32 {
                     ReplAction::Exit => {
                         return 0;
                     }
+                    ReplAction::FileProblem { filename, error } => {
+                        println!("{}", to_file_problem_report_string(filename, error));
+                    }
                     ReplAction::Help => {
                         println!("{TIPS}");
                     }

crates/repl_eval/src/gen.rs

@@ -53,7 +53,7 @@ pub fn compile_to_mono<'a, 'i, I: Iterator<Item = &'i str>>(
     palette: Palette,
 ) -> (Option<MonomorphizedModule<'a>>, Problems) {
     let filename = PathBuf::from("replfile.roc");
-    let src_dir = PathBuf::from("fake/test/path");
+    let src_dir = PathBuf::from(".");
     let (bytes_before_expr, module_src) = promote_expr_to_module(arena, defs, expr);
     let loaded = roc_load::load_and_monomorphize_from_str(
         arena,

crates/repl_ui/src/repl_state.rs

@@ -1,3 +1,6 @@
+use std::path::PathBuf;
+use std::{fs, io};
+
 use bumpalo::Bump;
 use roc_collections::MutSet;
 use roc_load::MonomorphizedModule;
@@ -14,9 +17,9 @@ use roc_reporting::report::Palette;
 use roc_target::Target;
 
 #[derive(Debug, Clone, PartialEq)]
-struct PastDef {
-    ident: String,
-    src: String,
+enum PastDef {
+    Def { ident: String, src: String },
+    Import(String),
 }
 
 pub struct ReplState {
@@ -39,6 +42,10 @@ pub enum ReplAction<'a> {
     },
     Exit,
     Help,
+    FileProblem {
+        filename: PathBuf,
+        error: io::ErrorKind,
+    },
     Nothing,
 }
 
@@ -134,9 +141,34 @@ impl ReplState {
                     ValueDef::ExpectFx { .. } => {
                         todo!("handle receiving an `expect-fx` - what should the repl do for that?")
                     }
-                    ValueDef::ModuleImport(_) => {
-                        todo!("handle importing a module from the REPL")
-                    }
+                    ValueDef::ModuleImport(import) => match import.name.value.package {
+                        Some(_) => {
+                            todo!("handle importing a module from a package")
+                        }
+                        None => {
+                            let mut filename = PathBuf::new();
+
+                            for part in import.name.value.name.parts() {
+                                filename.push(part);
+                            }
+
+                            filename.set_extension("roc");
+
+                            // Check we can read the file before we add it to past defs.
+                            // If we didn't do this, the bad import would remain in past_defs
+                            // and we'd report it on every subsequent evaluation.
+                            if let Err(err) = fs::metadata(&filename) {
+                                return ReplAction::FileProblem {
+                                    filename,
+                                    error: err.kind(),
+                                };
+                            }
+
+                            self.past_defs.push(PastDef::Import(line.to_string()));
+
+                            return ReplAction::Nothing;
+                        }
+                    },
                     ValueDef::IngestedFileImport(_) => {
                         todo!("handle ingesting a file from the REPL")
                     }
@@ -178,7 +210,10 @@ impl ReplState {
 
         let (opt_mono, problems) = compile_to_mono(
             arena,
-            self.past_defs.iter().map(|def| def.src.as_str()),
+            self.past_defs.iter().map(|past_def| match past_def {
+                PastDef::Def { ident: _, src } => src.as_str(),
+                PastDef::Import(src) => src.as_str(),
+            }),
             src,
             target,
             palette,
@@ -196,7 +231,7 @@ impl ReplState {
 
         existing_idents.insert(ident.clone());
 
-        self.past_defs.push(PastDef { ident, src });
+        self.past_defs.push(PastDef::Def { ident, src });
     }
 }
 

crates/repl_wasm/src/repl.rs

@@ -203,6 +203,9 @@ pub async fn entrypoint_from_js(src: String) -> String {
         ReplAction::Exit => {
             "To exit the web version of the REPL, just close the browser tab!".to_string()
         }
+        ReplAction::FileProblem { .. } => {
+            "The web version of the REPL cannot import files... for now!".to_string()
+        }
         ReplAction::Nothing => String::new(),
         ReplAction::Eval { opt_mono, problems } => {
             let opt_output = match opt_mono {