Clarifying behavior of rust-project.json source.include_dirs

[darichey]

I have a project structured like...

.
├── generated
│   └── foo.rs
├── rust-project.json
└── src
    └── lib.rs

I want to refer to the module foo from src/lib.rs. I thought I could do that with a rust-project.json that looks like...

{
  "crates": [
    {
      "display_name": "rust_test",
      "root_module": "./src/lib.rs",
      "edition": "2021",
      "is_workspace_member": true,
      "source": {
        "exclude_dirs": [],
        "include_dirs": ["./src", "./generated"]
      },
      "deps": []
    }
  ]
}

But mod foo; in src/lib.rs results in unresolved module, can't find module file: foo.rs, or foo/mod.rs.

I think this happens because the attempt to resolve the path to the module is relative to the original file:

rust-analyzer/crates/hir-def/src/nameres/mod_resolution.rs

Lines 92 to 95 in 2397e7a

	let orig_file_id = file_id.original_file_respecting_includes(db.upcast());
	for candidate in candidate_files.iter() {
	let path = AnchoredPath { anchor: orig_file_id, path: candidate.as_str() };
	if let Some(file_id) = db.resolve_path(path) {

so only paths in src are considered:

rust-analyzer/crates/vfs/src/file_set.rs

Lines 30 to 35 in 2397e7a

	pub fn resolve_path(&self, path: AnchoredPath<'_>) -> Option<FileId> {
	let mut base = self.paths[&path.anchor].clone();
	base.pop();
	let path = base.join(path.path)?;
	self.files.get(&path).copied()
	}

Should this work, or am I misunderstanding include_dirs?

[hauserx]

Resolving files across all include dirs would also help in case of bazel rules_rust, where a single crate may have mix of generated files and sources: bazelbuild/rules_rust#3126

Is extension of rust analyzer something that could be accepted?

[davidbarsky]

We should support that, but that’ll probably come with #18948. Our VFS/source root situation is suboptimal and I think we’d like to redesign this subsystem before doing one-off fixes. In recent weeks, seemingly small changes caused substantial breakage for users.

For what it’s worth, I imagine that resolving files across all include_dirs would be part of the initial redesign.