Merge #2887

2887: Initial auto import action implementation r=matklad a=SomeoneToIgnore

Closes https://github.com/rust-analyzer/rust-analyzer/issues/2180

Adds an auto import action implementation.

This implementation is not ideal and has a few limitations:

* The import search functionality should be moved into a separate crate accessible from ra_assists.
This requires a lot of changes and a preliminary design. 
Currently the functionality is provided as a trait impl, more on that here: https://github.com/rust-analyzer/rust-analyzer/issues/2180#issuecomment-575690942

* Due to the design desicion from the previous item, no doctests are run for the new aciton (look for a new FIXME in the PR)

* For the same reason, I have to create the mock trait implementaion to test the assist

* Ideally, I think we should have this feature as a diagnostics (that detects an absense of an import) that has a corresponding quickfix action that gets evaluated on demand.
Curretly we perform the import search every time we resolve the import which looks suboptimal.
This requires `classify_name_ref` to be moved from ra_ide, so not done currently.

A few improvements to the imports mechanism to be considered later:

* Constants like `ra_syntax::SyntaxKind::NAME` are not imported, because they are not present in the database

* Method usages are not imported, they are found in the database, but `find_use_path` does not return any import paths for them

* Some import paths returned by the `find_use_path` method end up in `core::` or `alloc::` instead of `std:`, for example: `core::fmt::Debug` instead of `std::fmt::Debug`.
This is not an error techically, but still looks weird.

* No detection of cases where a trait should be imported in order to be able to call a method

* Improve `auto_import_text_edit` functionality: refactor it and move away from the place it is now, add better logic for merging the new import with already existing imports

Co-authored-by: Kirill Bulatov <[email protected]>

3 files changed, 81 insertions, 3 deletions

diff --git a/crates/ra_ide/src/assists.rs b/crates/ra_ide/src/assists.rs
index a936900da..c43c45c65 100644
--- a/crates/ra_ide/src/assists.rs
+++ b/crates/ra_ide/src/assists.rs
@@ -2,8 +2,9 @@
 
 use ra_db::{FilePosition, FileRange};
 
-use crate::{db::RootDatabase, FileId, SourceChange, SourceFileEdit};
-
+use crate::{
+    db::RootDatabase, imports_locator::ImportsLocatorIde, FileId, SourceChange, SourceFileEdit,
+};
 use either::Either;
 pub use ra_assists::AssistId;
 use ra_assists::{AssistAction, AssistLabel};
@@ -16,7 +17,7 @@ pub struct Assist {
 }
 
 pub(crate) fn assists(db: &RootDatabase, frange: FileRange) -> Vec<Assist> {
-    ra_assists::assists(db, frange)
+    ra_assists::assists_with_imports_locator(db, frange, ImportsLocatorIde::new(db))
         .into_iter()
         .map(|assist| {
             let file_id = frange.file_id;
diff --git a/crates/ra_ide/src/imports_locator.rs b/crates/ra_ide/src/imports_locator.rs
new file mode 100644
index 000000000..48b014c7d
--- /dev/null
+++ b/crates/ra_ide/src/imports_locator.rs
@@ -0,0 +1,76 @@
+//! This module contains an import search funcionality that is provided to the ra_assists module.
+//! Later, this should be moved away to a separate crate that is accessible from the ra_assists module.
+
+use crate::{
+    db::RootDatabase,
+    references::{classify_name, NameDefinition, NameKind},
+    symbol_index::{self, FileSymbol},
+    Query,
+};
+use hir::{db::HirDatabase, ModuleDef, SourceBinder};
+use ra_assists::ImportsLocator;
+use ra_prof::profile;
+use ra_syntax::{ast, AstNode, SyntaxKind::NAME};
+
+pub(crate) struct ImportsLocatorIde<'a> {
+    source_binder: SourceBinder<'a, RootDatabase>,
+}
+
+impl<'a> ImportsLocatorIde<'a> {
+    pub(crate) fn new(db: &'a RootDatabase) -> Self {
+        Self { source_binder: SourceBinder::new(db) }
+    }
+
+    fn get_name_definition(
+        &mut self,
+        db: &impl HirDatabase,
+        import_candidate: &FileSymbol,
+    ) -> Option<NameDefinition> {
+        let _p = profile("get_name_definition");
+        let file_id = import_candidate.file_id.into();
+        let candidate_node = import_candidate.ptr.to_node(&db.parse_or_expand(file_id)?);
+        let candidate_name_node = if candidate_node.kind() != NAME {
+            candidate_node.children().find(|it| it.kind() == NAME)?
+        } else {
+            candidate_node
+        };
+        classify_name(
+            &mut self.source_binder,
+            hir::InFile { file_id, value: &ast::Name::cast(candidate_name_node)? },
+        )
+    }
+}
+
+impl ImportsLocator for ImportsLocatorIde<'_> {
+    fn find_imports(&mut self, name_to_import: &str) -> Vec<ModuleDef> {
+        let _p = profile("search_for_imports");
+        let db = self.source_binder.db;
+
+        let project_results = {
+            let mut query = Query::new(name_to_import.to_string());
+            query.exact();
+            query.limit(40);
+            symbol_index::world_symbols(db, query)
+        };
+        let lib_results = {
+            let mut query = Query::new(name_to_import.to_string());
+            query.libs();
+            query.exact();
+            query.limit(40);
+            symbol_index::world_symbols(db, query)
+        };
+
+        project_results
+            .into_iter()
+            .chain(lib_results.into_iter())
+            .filter_map(|import_candidate| self.get_name_definition(db, &import_candidate))
+            .filter_map(|name_definition_to_import| {
+                if let NameKind::Def(module_def) = name_definition_to_import.kind {
+                    Some(module_def)
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+}
diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 62fe6d2a9..03ad6b2c1 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -30,6 +30,7 @@ mod syntax_highlighting;
 mod parent_module;
 mod references;
 mod impls;
+mod imports_locator;
 mod assists;
 mod diagnostics;
 mod syntax_tree;