feat: mod.nr entrypoint (noir-lang#5039)

# Description

## Problem\*

Resolves noir-lang#4860

## Summary\*

Allow using `mod.nr` as the entrypoint to a module.

- [x] Add test for conflicting `foo.nr` and `foo/mod.nr`
- [x] Add handling for `foo/lib/foo.nr` and other disallowed name-based
cases
- [x] Add tests for `foo/lib/foo.nr`, `main/foo.nr`, and `foo/mod/bar`

## Additional Context

I expected `find_module` to have the logic for this, but after a bunch
of debugging, it seems somehow unrelated. I.e. it's not even called for
the `mod.nr` case.

## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: TomAFrench <[email protected]>
Co-authored-by: Tom French <[email protected]>
Co-authored-by: Ary Borenszweig <[email protected]>

compiler/fm/Cargo.toml

@@ -13,5 +13,4 @@ codespan-reporting.workspace = true
 serde.workspace = true
 
 [dev-dependencies]
-tempfile.workspace = true
 iter-extended.workspace = true

compiler/fm/src/lib.rs

@@ -185,24 +185,17 @@ mod path_normalization {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use tempfile::{tempdir, TempDir};
 
-    // Returns the absolute path to the file
-    fn create_dummy_file(dir: &TempDir, file_name: &Path) -> PathBuf {
-        let file_path = dir.path().join(file_name);
-        let _file = std::fs::File::create(&file_path).unwrap();
-        file_path
+    fn add_file(fm: &mut FileManager, file_name: &Path) -> FileId {
+        fm.add_file_with_source(file_name, "fn foo() {}".to_string()).unwrap()
     }
 
     #[test]
     fn path_resolve_file_module_other_ext() {
-        let dir = tempdir().unwrap();
-        let file_name = Path::new("foo.nr");
-        create_dummy_file(&dir, file_name);
+        let dir = PathBuf::new();
+        let mut fm = FileManager::new(&dir);
 
-        let mut fm = FileManager::new(dir.path());
-
-        let file_id = fm.add_file_with_source(file_name, "fn foo() {}".to_string()).unwrap();
+        let file_id = add_file(&mut fm, &dir.join("foo.nr"));
 
         assert!(fm.path(file_id).unwrap().ends_with("foo.nr"));
     }
@@ -213,23 +206,19 @@ mod tests {
     /// they should both resolve to ../foo.nr
     #[test]
     fn path_resolve_modules_with_different_paths_as_same_file() {
-        let dir = tempdir().unwrap();
-        let sub_dir = TempDir::new_in(&dir).unwrap();
-        let sub_sub_dir = TempDir::new_in(&sub_dir).unwrap();
-
-        let mut fm = FileManager::new(dir.path());
-
-        // Create a lib.nr file at the root.
-        let file_name = Path::new("lib.nr");
-        create_dummy_file(&dir, file_name);
-
-        // Create another path with `./` and `../` inside it
-        let second_file_name = PathBuf::from(sub_sub_dir.path()).join("./../../lib.nr");
-
-        // Add both files to the file manager
-        let file_id = fm.add_file_with_source(file_name, "fn foo() {}".to_string()).unwrap();
-        let second_file_id =
-            fm.add_file_with_source(&second_file_name, "fn foo() {}".to_string()).unwrap();
+        let dir = PathBuf::new();
+        let mut fm = FileManager::new(&dir);
+
+        // Create a lib.nr file at the root and add it to the file manager.
+        let file_id = add_file(&mut fm, &dir.join("lib.nr"));
+
+        // Create another path with `./` and `../` inside it, and add it to the file manager
+        let sub_dir = dir.join("sub_dir");
+        let sub_sub_dir = sub_dir.join("sub_sub_dir");
+        let second_file_id = add_file(
+            &mut fm,
+            PathBuf::from(sub_sub_dir.as_path()).join("./../../lib.nr").as_path(),
+        );
 
         assert_eq!(file_id, second_file_id);
     }

compiler/noirc_frontend/Cargo.toml

@@ -36,7 +36,6 @@ lalrpop-util = { version = "0.20.2", features = ["lexer"] }
 base64.workspace = true
 strum = "0.24"
 strum_macros = "0.24"
-tempfile.workspace = true
 
 [build-dependencies]
 lalrpop = "0.20.2"