1 files changed, 155 insertions, 0 deletions

diff --git a/crates/ide/src/parent_module.rs b/crates/ide/src/parent_module.rs
new file mode 100644
index 000000000..59ed2967c
--- /dev/null
+++ b/crates/ide/src/parent_module.rs
@@ -0,0 +1,155 @@
+use base_db::{CrateId, FileId, FilePosition};
+use hir::Semantics;
+use ide_db::RootDatabase;
+use syntax::{
+    algo::find_node_at_offset,
+    ast::{self, AstNode},
+};
+use test_utils::mark;
+
+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**
+// |===
+
+/// This returns `Vec` because a module may be included from several places. We
+/// don't handle this case yet though, so the Vec has length at most one.
+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))
+        {
+            mark::hit!(test_resolve_parent_module_on_module_decl);
+            module = m.syntax().ancestors().skip(1).find_map(ast::Module::cast);
+        }
+    }
+
+    let module = match module {
+        Some(module) => sema.to_def(&module),
+        None => sema.to_module_def(position.file_id),
+    };
+    let module = match module {
+        None => return Vec::new(),
+        Some(it) => it,
+    };
+    let nav = NavigationTarget::from_module_to_decl(db, module);
+    vec![nav]
+}
+
+/// 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);
+    let module = match sema.to_module_def(file_id) {
+        Some(it) => it,
+        None => return Vec::new(),
+    };
+    let krate = module.krate();
+    vec![krate.into()]
+}
+
+#[cfg(test)]
+mod tests {
+    use base_db::Env;
+    use cfg::CfgOptions;
+    use test_utils::mark;
+
+    use crate::{
+        mock_analysis::{analysis_and_position, MockAnalysis},
+        AnalysisChange, CrateGraph,
+        Edition::Edition2018,
+    };
+
+    #[test]
+    fn test_resolve_parent_module() {
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            mod foo;
+            //- /foo.rs
+            <|>// empty
+            ",
+        );
+        let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
+        nav.assert_match("foo MODULE FileId(1) 0..8");
+    }
+
+    #[test]
+    fn test_resolve_parent_module_on_module_decl() {
+        mark::check!(test_resolve_parent_module_on_module_decl);
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            mod foo;
+
+            //- /foo.rs
+            mod <|>bar;
+
+            //- /foo/bar.rs
+            // empty
+            ",
+        );
+        let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
+        nav.assert_match("foo MODULE FileId(1) 0..8");
+    }
+
+    #[test]
+    fn test_resolve_parent_module_for_inline() {
+        let (analysis, pos) = analysis_and_position(
+            "
+            //- /lib.rs
+            mod foo {
+                mod bar {
+                    mod baz { <|> }
+                }
+            }
+            ",
+        );
+        let nav = analysis.parent_module(pos).unwrap().pop().unwrap();
+        nav.assert_match("baz MODULE FileId(1) 32..44");
+    }
+
+    #[test]
+    fn test_resolve_crate_root() {
+        let mock = MockAnalysis::with_files(
+            r#"
+//- /bar.rs
+mod foo;
+//- /foo.rs
+// empty
+"#,
+        );
+        let root_file = mock.id_of("/bar.rs");
+        let mod_file = mock.id_of("/foo.rs");
+        let mut host = mock.analysis_host();
+        assert!(host.analysis().crate_for(mod_file).unwrap().is_empty());
+
+        let mut crate_graph = CrateGraph::default();
+        let crate_id = crate_graph.add_crate_root(
+            root_file,
+            Edition2018,
+            None,
+            CfgOptions::default(),
+            Env::default(),
+            Default::default(),
+        );
+        let mut change = AnalysisChange::new();
+        change.set_crate_graph(crate_graph);
+        host.apply_change(change);
+
+        assert_eq!(host.analysis().crate_for(mod_file).unwrap(), vec![crate_id]);
+    }
+}