fix self_named_module_files: track module with relative path

tracks each sub folder by its relative path from crate's working
directory instead of individual path segments

changelog: none

Signed-off-by: Zihan <[email protected]>

Author: zihan0822

clippy_lints/src/module_style.rs

@@ -5,8 +5,7 @@ use rustc_lint::{EarlyContext, EarlyLintPass, Level, LintContext};
 use rustc_session::impl_lint_pass;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::{FileName, SourceFile, Span, SyntaxContext};
-use std::ffi::OsStr;
-use std::path::{Component, Path};
+use std::path::Path;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -85,13 +84,12 @@ impl EarlyLintPass for ModStyle {
             return;
         };
 
-        // `folder_segments` is all unique folder path segments `path/to/foo.rs` gives
-        // `[path, to]` but not foo
-        let mut folder_segments = FxIndexSet::default();
+        // `sub_folders` is all the sub folders under `src` directory including `src`
+        let mut sub_folders = FxIndexSet::default();
         // `mod_folders` is all the unique folder names that contain a mod.rs file
         let mut mod_folders = FxHashSet::default();
-        // `file_map` maps file names to the full path including the file name
-        // `{ foo => path/to/foo.rs, .. }
+        // `file_map` maps file names with `.rs` extension excluded to file path and
+        // `rustc_span::SourceFile`.
         let mut file_map = FxHashMap::default();
         for file in files.iter() {
             if let FileName::Real(name) = &file.name
@@ -109,16 +107,13 @@ impl EarlyLintPass for ModStyle {
                 } else {
                     continue;
                 };
-
-                if let Some(stem) = path.file_stem() {
-                    file_map.insert(stem, (file, path));
-                }
-                process_paths_for_mod_files(path, &mut folder_segments, &mut mod_folders);
+                file_map.insert(path.with_extension(""), (file, path));
+                process_paths_for_mod_files(path, &mut sub_folders, &mut mod_folders);
                 check_self_named_mod_exists(cx, path, file);
             }
         }
 
-        for folder in &folder_segments {
+        for folder in sub_folders {
             if !mod_folders.contains(folder)
                 && let Some((file, path)) = file_map.get(folder)
             {
@@ -128,9 +123,7 @@ impl EarlyLintPass for ModStyle {
                     Span::new(file.start_pos, file.start_pos, SyntaxContext::root(), None),
                     format!("`mod.rs` files are required, found `{}`", path.display()),
                     |diag| {
-                        let mut correct = path.to_path_buf();
-                        correct.pop();
-                        correct.push(folder);
+                        let mut correct = folder.to_path_buf();
                         correct.push("mod.rs");
                         diag.help(format!("move `{}` to `{}`", path.display(), correct.display(),));
                     },
@@ -140,20 +133,19 @@ impl EarlyLintPass for ModStyle {
     }
 }
 
-/// For each `path` we add each folder component to `folder_segments` and if the file name
-/// is `mod.rs` we add it's parent folder to `mod_folders`.
+/// Adds sub folder path relative to crate's working folder to `folders`.
+/// If `path` is a `mod.rs`, its parent folder is added to `mod_folders`.
 fn process_paths_for_mod_files<'a>(
     path: &'a Path,
-    folder_segments: &mut FxIndexSet<&'a OsStr>,
-    mod_folders: &mut FxHashSet<&'a OsStr>,
+    folders: &mut FxIndexSet<&'a Path>,
+    mod_folders: &mut FxHashSet<&'a Path>,
 ) {
-    let mut comp = path.components().rev().peekable();
-    let _: Option<_> = comp.next();
+    let mut comp = path.components();
+    let _: Option<_> = comp.next_back();
     if path.ends_with("mod.rs") {
-        mod_folders.insert(comp.peek().map(|c| c.as_os_str()).unwrap_or_default());
+        mod_folders.insert(comp.as_path());
     }
-    let folders = comp.filter_map(|c| if let Component::Normal(s) = c { Some(s) } else { None });
-    folder_segments.extend(folders);
+    folders.insert(comp.as_path());
 }
 
 /// Checks every path for the presence of `mod.rs` files and emits the lint if found.

tests/ui-cargo/module_style/duplicated_mod_names_14697/Cargo.stderr

@@ -0,0 +1,11 @@
+error: `mod.rs` files are required, found `src/foo.rs`
+ --> src/foo.rs:1:1
+  |
+1 | pub mod bar;
+  | ^
+  |
+  = help: move `src/foo.rs` to `src/foo/mod.rs`
+  = note: `-D clippy::self-named-module-files` implied by `-D warnings`
+  = help: to override `-D warnings` add `#[allow(clippy::self_named_module_files)]`
+
+error: could not compile `duplicated-mod-names-14697` (lib) due to 1 previous error

tests/ui-cargo/module_style/duplicated_mod_names_14697/Cargo.toml

@@ -0,0 +1,11 @@
+# Should trigger when multiple mods with the same name exist and not all of them follow self-named convention.
+# See issue #14697.
+[package]
+name = "duplicated-mod-names-14697"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

tests/ui-cargo/module_style/duplicated_mod_names_14697/src/foo.rs

@@ -0,0 +1 @@
+pub mod bar;

tests/ui-cargo/module_style/duplicated_mod_names_14697/src/foo/bar.rs

@@ -0,0 +1 @@
+

tests/ui-cargo/module_style/duplicated_mod_names_14697/src/lib.rs

@@ -0,0 +1,4 @@
+#![warn(clippy::self_named_module_files)]
+
+pub mod foo;
+pub mod other;

tests/ui-cargo/module_style/duplicated_mod_names_14697/src/other/foo/mod.rs

@@ -0,0 +1 @@
+

tests/ui-cargo/module_style/duplicated_mod_names_14697/src/other/mod.rs

@@ -0,0 +1 @@
+pub mod foo;

tests/ui-cargo/module_style/segment_with_mod_name_10271_11916/Cargo.toml

@@ -0,0 +1,10 @@
+# Should not produce FP when irrelavant path segment shares the same name with module.
+# See issue #10271 and #11916.
+[package]
+name = "segment-with-mod-name-10271-11916"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[workspace]
+members = ["foo/bar"]

tests/ui-cargo/module_style/segment_with_mod_name_10271_11916/foo/bar/Cargo.toml

@@ -0,0 +1,5 @@
+[package]
+name = "bar"
+version = "0.1.0"
+edition = "2024"
+publish = false