2 files changed, 42 insertions, 10 deletions

diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 5314a333e..c872b0dc4 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -4,9 +4,9 @@ use gen_lsp_server::ErrorCode;
 use languageserver_types::{
     CodeActionResponse, Command, CompletionItem, CompletionItemKind, Diagnostic,
     DiagnosticSeverity, DocumentSymbol, Documentation, FoldingRange, FoldingRangeKind,
-    FoldingRangeParams, InsertTextFormat, Location, MarkupContent, MarkupKind, Position,
+    FoldingRangeParams, InsertTextFormat, Location, MarkupContent, MarkupKind, MarkedString, Position,
     PrepareRenameResponse, RenameParams, SymbolInformation, TextDocumentIdentifier, TextEdit,
-    WorkspaceEdit, ParameterInformation, SignatureInformation,
+    WorkspaceEdit, ParameterInformation, SignatureInformation, Hover, HoverContents,
 };
 use ra_analysis::{FileId, FoldKind, Query, RunnableKind, FilePosition};
 use ra_syntax::text_utils::contains_offset_nonstrict;
@@ -478,6 +478,30 @@ pub fn handle_signature_help(
     }
 }
 
+pub fn handle_hover(
+    world: ServerWorld,
+    params: req::TextDocumentPositionParams,
+) -> Result<Option<Hover>> {
+    let position = params.try_conv_with(&world)?;
+    let line_index = world.analysis().file_line_index(position.file_id);
+
+    for (file_id, symbol) in world.analysis().approximately_resolve_symbol(position)? {
+        let range = symbol.node_range.conv_with(&line_index);
+        let comment = world.analysis.doc_comment_for(file_id, symbol)?;
+
+        if comment.is_some() {
+            let contents = HoverContents::Scalar(MarkedString::String(comment.unwrap()));
+
+            return Ok(Some(Hover {
+                contents,
+                range: Some(range),
+            }));
+        }
+    }
+
+    Ok(None)
+}
+
 pub fn handle_prepare_rename(
     world: ServerWorld,
     params: req::TextDocumentPositionParams,
diff --git a/crates/ra_lsp_server/src/main_loop/mod.rs b/crates/ra_lsp_server/src/main_loop/mod.rs
index 229d1b0f7..78d93741a 100644
--- a/crates/ra_lsp_server/src/main_loop/mod.rs
+++ b/crates/ra_lsp_server/src/main_loop/mod.rs
@@ -48,6 +48,7 @@ enum Task {
 pub fn main_loop(
     internal_mode: bool,
     root: PathBuf,
+    publish_decorations: bool,
     msg_receiver: &Receiver<RawMessage>,
     msg_sender: &Sender<RawMessage>,
 ) -> Result<()> {
@@ -67,6 +68,7 @@ pub fn main_loop(
     let mut subs = Subscriptions::new();
     let main_res = main_loop_inner(
         internal_mode,
+        publish_decorations,
         root,
         &pool,
         msg_sender,
@@ -99,6 +101,7 @@ pub fn main_loop(
 
 fn main_loop_inner(
     internal_mode: bool,
+    publish_decorations: bool,
     ws_root: PathBuf,
     pool: &ThreadPool,
     msg_sender: &Sender<RawMessage>,
@@ -210,6 +213,7 @@ fn main_loop_inner(
             update_file_notifications_on_threadpool(
                 pool,
                 state.snapshot(),
+                publish_decorations,
                 task_sender.clone(),
                 subs.subscriptions(),
             )
@@ -259,6 +263,7 @@ fn on_request(
         .on::<req::CodeActionRequest>(handlers::handle_code_action)?
         .on::<req::FoldingRangeRequest>(handlers::handle_folding_range)?
         .on::<req::SignatureHelpRequest>(handlers::handle_signature_help)?
+        .on::<req::HoverRequest>(handlers::handle_hover)?
         .on::<req::PrepareRenameRequest>(handlers::handle_prepare_rename)?
         .on::<req::Rename>(handlers::handle_rename)?
         .on::<req::References>(handlers::handle_references)?
@@ -415,6 +420,7 @@ impl<'a> PoolDispatcher<'a> {
 fn update_file_notifications_on_threadpool(
     pool: &ThreadPool,
     world: ServerWorld,
+    publish_decorations: bool,
     sender: Sender<Task>,
     subscriptions: Vec<FileId>,
 ) {
@@ -431,15 +437,17 @@ fn update_file_notifications_on_threadpool(
                     sender.send(Task::Notify(not));
                 }
             }
-            match handlers::publish_decorations(&world, file_id) {
-                Err(e) => {
-                    if !is_canceled(&e) {
-                        error!("failed to compute decorations: {:?}", e);
+            if publish_decorations {
+                match handlers::publish_decorations(&world, file_id) {
+                    Err(e) => {
+                        if !is_canceled(&e) {
+                            error!("failed to compute decorations: {:?}", e);
+                        }
+                    }
+                    Ok(params) => {
+                        let not = RawNotification::new::<req::PublishDecorations>(&params);
+                        sender.send(Task::Notify(not))
                     }
-                }
-                Ok(params) => {
-                    let not = RawNotification::new::<req::PublishDecorations>(&params);
-                    sender.send(Task::Notify(not))
                 }
             }
         }