1 files changed, 167 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide/src/parent_module.rs b/src/tools/rust-analyzer/crates/ide/src/parent_module.rs
new file mode 100644
index 000000000..9b1f48044
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide/src/parent_module.rs
@@ -0,0 +1,167 @@
+use hir::Semantics;
+use ide_db::{
+    base_db::{CrateId, FileId, FilePosition},
+    RootDatabase,
+};
+use itertools::Itertools;
+use syntax::{
+    algo::find_node_at_offset,
+    ast::{self, AstNode},
+};
+
+use crate::NavigationTarget;
+
+// Feature: Parent Module
+//
+// Navigates to the parent module of the current module.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: Locate parent module**
+// |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065580-04c21800-91b1-11eb-9a32-00086161c0bd.gif[]
+
+/// This returns `Vec` because a module may be included from several places.
+pub(crate) fn parent_module(db: &RootDatabase, position: FilePosition) -> Vec<NavigationTarget> {
+    let sema = Semantics::new(db);
+    let source_file = sema.parse(position.file_id);
+
+    let mut module = find_node_at_offset::<ast::Module>(source_file.syntax(), position.offset);
+
+    // If cursor is literally on `mod foo`, go to the grandpa.
+    if let Some(m) = &module {
+        if !m
+            .item_list()
+            .map_or(false, |it| it.syntax().text_range().contains_inclusive(position.offset))
+        {
+            cov_mark::hit!(test_resolve_parent_module_on_module_decl);
+            module = m.syntax().ancestors().skip(1).find_map(ast::Module::cast);
+        }
+    }
+
+    match module {
+        Some(module) => sema
+            .to_def(&module)
+            .into_iter()
+            .map(|module| NavigationTarget::from_module_to_decl(db, module))
+            .collect(),
+        None => sema
+            .to_module_defs(position.file_id)
+            .map(|module| NavigationTarget::from_module_to_decl(db, module))
+            .collect(),
+    }
+}
+
+/// Returns `Vec` for the same reason as `parent_module`
+pub(crate) fn crate_for(db: &RootDatabase, file_id: FileId) -> Vec<CrateId> {
+    let sema = Semantics::new(db);
+    sema.to_module_defs(file_id).map(|module| module.krate().into()).unique().collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use ide_db::base_db::FileRange;
+
+    use crate::fixture;
+
+    fn check(ra_fixture: &str) {
+        let (analysis, position, expected) = fixture::annotations(ra_fixture);
+        let navs = analysis.parent_module(position).unwrap();
+        let navs = navs
+            .iter()
+            .map(|nav| FileRange { file_id: nav.file_id, range: nav.focus_or_full_range() })
+            .collect::<Vec<_>>();
+        assert_eq!(expected.into_iter().map(|(fr, _)| fr).collect::<Vec<_>>(), navs);
+    }
+
+    #[test]
+    fn test_resolve_parent_module() {
+        check(
+            r#"
+//- /lib.rs
+mod foo;
+  //^^^
+
+//- /foo.rs
+$0// empty
+"#,
+        );
+    }
+
+    #[test]
+    fn test_resolve_parent_module_on_module_decl() {
+        cov_mark::check!(test_resolve_parent_module_on_module_decl);
+        check(
+            r#"
+//- /lib.rs
+mod foo;
+  //^^^
+//- /foo.rs
+mod $0bar;
+
+//- /foo/bar.rs
+// empty
+"#,
+        );
+    }
+
+    #[test]
+    fn test_resolve_parent_module_for_inline() {
+        check(
+            r#"
+//- /lib.rs
+mod foo {
+    mod bar {
+        mod baz { $0 }
+    }     //^^^
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn test_resolve_multi_parent_module() {
+        check(
+            r#"
+//- /main.rs
+mod foo;
+  //^^^
+#[path = "foo.rs"]
+mod bar;
+  //^^^
+//- /foo.rs
+$0
+"#,
+        );
+    }
+
+    #[test]
+    fn test_resolve_crate_root() {
+        let (analysis, file_id) = fixture::file(
+            r#"
+//- /foo.rs
+$0
+//- /main.rs
+mod foo;
+"#,
+        );
+        assert_eq!(analysis.crate_for(file_id).unwrap().len(), 1);
+    }
+
+    #[test]
+    fn test_resolve_multi_parent_crate() {
+        let (analysis, file_id) = fixture::file(
+            r#"
+//- /baz.rs
+$0
+//- /foo.rs crate:foo
+mod baz;
+//- /bar.rs crate:bar
+mod baz;
+"#,
+        );
+        assert_eq!(analysis.crate_for(file_id).unwrap().len(), 2);
+    }
+}