Merge #6553

6553: Auto imports in completion r=matklad a=SomeoneToIgnore

![completion](https://user-images.githubusercontent.com/2690773/99155339-ae4fb380-26bf-11eb-805a-655b1706ce70.gif)

Closes https://github.com/rust-analyzer/rust-analyzer/issues/1062 but does not handle the completion order, since it's a separate task for https://github.com/rust-analyzer/rust-analyzer/issues/4922 , https://github.com/rust-analyzer/rust-analyzer/issues/4922 and maybe something else.

2 quirks in the current implementation:

* traits are not auto imported during method completion

If I understand the current situation right, we cannot search for traits by a **part** of a method name, we need a full name with correct case to get a trait for it.

* VSCode (?) autocompletion is not as rigid as in Intellij Rust as you can notice on the animation.

Intellij is able to refresh the completions on every new symbol added, yet VS Code does not query the completions on every symbol for me.
With a few debug prints placed in RA, I've observed the following behaviour: after the first set of completion suggestions is received, next symbol input does not trigger a server request, if the completions contain this symbol.
When more symbols added, the existing completion suggestions are filtered out until none are left and only then, on the next symbol it queries for completions.
It seems like the only alternative to get an updated set of results is to manually retrigger it with Esc and Ctrl + Space.

Despite the eerie latter bullet, the completion seems to work pretty fine and fast nontheless, but if you have any ideas on how to make it more smooth, I'll gladly try it out.

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

1 files changed, 47 insertions, 13 deletions

diff --git a/crates/ide_db/src/imports_locator.rs b/crates/ide_db/src/imports_locator.rs
index df74be00b..9d8ea7368 100644
--- a/crates/ide_db/src/imports_locator.rs
+++ b/crates/ide_db/src/imports_locator.rs
@@ -1,36 +1,70 @@
 //! This module contains an import search funcionality that is provided to the assists module.
 //! Later, this should be moved away to a separate crate that is accessible from the assists module.
 
-use hir::{Crate, MacroDef, ModuleDef, Semantics};
+use hir::{import_map, Crate, MacroDef, ModuleDef, Semantics};
 use syntax::{ast, AstNode, SyntaxKind::NAME};
 
 use crate::{
     defs::{Definition, NameClass},
-    symbol_index::{self, FileSymbol, Query},
+    symbol_index::{self, FileSymbol},
     RootDatabase,
 };
 use either::Either;
 use rustc_hash::FxHashSet;
 
-pub fn find_imports<'a>(
+pub fn find_exact_imports<'a>(
     sema: &Semantics<'a, RootDatabase>,
     krate: Crate,
     name_to_import: &str,
-) -> Vec<Either<ModuleDef, MacroDef>> {
-    let _p = profile::span("search_for_imports");
+) -> impl Iterator<Item = Either<ModuleDef, MacroDef>> {
+    let _p = profile::span("find_exact_imports");
+    find_imports(
+        sema,
+        krate,
+        {
+            let mut local_query = symbol_index::Query::new(name_to_import.to_string());
+            local_query.exact();
+            local_query.limit(40);
+            local_query
+        },
+        import_map::Query::new(name_to_import).anchor_end().case_sensitive().limit(40),
+    )
+}
+
+pub fn find_similar_imports<'a>(
+    sema: &Semantics<'a, RootDatabase>,
+    krate: Crate,
+    name_to_import: &str,
+    limit: usize,
+) -> impl Iterator<Item = Either<ModuleDef, MacroDef>> {
+    let _p = profile::span("find_similar_imports");
+    find_imports(
+        sema,
+        krate,
+        {
+            let mut local_query = symbol_index::Query::new(name_to_import.to_string());
+            local_query.limit(limit);
+            local_query
+        },
+        import_map::Query::new(name_to_import).limit(limit),
+    )
+}
+
+fn find_imports<'a>(
+    sema: &Semantics<'a, RootDatabase>,
+    krate: Crate,
+    local_query: symbol_index::Query,
+    external_query: import_map::Query,
+) -> impl Iterator<Item = Either<ModuleDef, MacroDef>> {
+    let _p = profile::span("find_similar_imports");
     let db = sema.db;
 
     // Query dependencies first.
     let mut candidates: FxHashSet<_> =
-        krate.query_external_importables(db, name_to_import).collect();
+        krate.query_external_importables(db, external_query).collect();
 
     // Query the local crate using the symbol index.
-    let local_results = {
-        let mut query = Query::new(name_to_import.to_string());
-        query.exact();
-        query.limit(40);
-        symbol_index::crate_symbols(db, krate.into(), query)
-    };
+    let local_results = symbol_index::crate_symbols(db, krate.into(), local_query);
 
     candidates.extend(
         local_results
@@ -43,7 +77,7 @@ pub fn find_imports<'a>(
             }),
     );
 
-    candidates.into_iter().collect()
+    candidates.into_iter()
 }
 
 fn get_name_definition<'a>(