4 files changed, 33 insertions, 1 deletions

diff --git a/crates/server/src/caps.rs b/crates/server/src/caps.rs
index ffebd9b47..98499bb05 100644
--- a/crates/server/src/caps.rs
+++ b/crates/server/src/caps.rs
@@ -4,6 +4,7 @@ use languageserver_types::{
     TextDocumentSyncOptions,
     TextDocumentSyncKind,
     ExecuteCommandOptions,
+    CompletionOptions,
 };
 
 pub fn server_capabilities() -> ServerCapabilities {
@@ -18,7 +19,10 @@ pub fn server_capabilities() -> ServerCapabilities {
             }
         )),
         hover_provider: None,
-        completion_provider: None,
+        completion_provider: Some(CompletionOptions {
+            resolve_provider: None,
+            trigger_characters: None,
+        }),
         signature_help_provider: None,
         definition_provider: Some(true),
         type_definition_provider: None,
diff --git a/crates/server/src/main_loop/handlers.rs b/crates/server/src/main_loop/handlers.rs
index b68e93e46..e7ac53028 100644
--- a/crates/server/src/main_loop/handlers.rs
+++ b/crates/server/src/main_loop/handlers.rs
@@ -4,6 +4,7 @@ use languageserver_types::{
     Diagnostic, DiagnosticSeverity, Url, DocumentSymbol,
     Command, TextDocumentIdentifier, WorkspaceEdit,
     SymbolInformation, Position, Location, TextEdit,
+    CompletionItem,
 };
 use serde_json::{to_value, from_value};
 use libanalysis::{Query};
@@ -259,6 +260,28 @@ pub fn handle_parent_module(
     Ok(res)
 }
 
+pub fn handle_completion(
+    world: ServerWorld,
+    params: req::CompletionParams,
+) -> Result<Option<req::CompletionResponse>> {
+    let file_id = params.text_document.try_conv_with(&world)?;
+    let file = world.analysis().file_syntax(file_id)?;
+    let line_index = world.analysis().file_line_index(file_id)?;
+    let offset = params.position.conv_with(&line_index);
+    let items = match libeditor::scope_completion(&file, offset) {
+        None => return Ok(None),
+        Some(items) => items,
+    };
+    let items = items.into_iter()
+        .map(|item| CompletionItem {
+            label: item.name,
+            .. Default::default()
+        })
+        .collect();
+
+    Ok(Some(req::CompletionResponse::Array(items)))
+}
+
 pub fn handle_execute_command(
     world: ServerWorld,
     mut params: req::ExecuteCommandParams,
diff --git a/crates/server/src/main_loop/mod.rs b/crates/server/src/main_loop/mod.rs
index 1e65041e2..5213ecc04 100644
--- a/crates/server/src/main_loop/mod.rs
+++ b/crates/server/src/main_loop/mod.rs
@@ -28,6 +28,7 @@ use {
         handle_find_matching_brace,
         handle_parent_module,
         handle_join_lines,
+        handle_completion,
     },
 };
 
@@ -143,6 +144,9 @@ fn on_request(
     handle_request_on_threadpool::<req::GotoDefinition>(
         &mut req, pool, world, sender, handle_goto_definition,
     )?;
+    handle_request_on_threadpool::<req::Completion>(
+        &mut req, pool, world, sender, handle_completion,
+    )?;
     handle_request_on_threadpool::<req::ParentModule>(
         &mut req, pool, world, sender, handle_parent_module,
     )?;
diff --git a/crates/server/src/req.rs b/crates/server/src/req.rs
index c431deeb4..6d3466b66 100644
--- a/crates/server/src/req.rs
+++ b/crates/server/src/req.rs
@@ -11,6 +11,7 @@ pub use languageserver_types::{
     WorkspaceSymbolParams,
     TextDocumentPositionParams,
     TextEdit,
+    CompletionParams, CompletionResponse,
 };