3 files changed, 65 insertions, 39 deletions

diff --git a/crates/ra_lsp_server/src/lib.rs b/crates/ra_lsp_server/src/lib.rs
index 1208c1343..a3464a5a3 100644
--- a/crates/ra_lsp_server/src/lib.rs
+++ b/crates/ra_lsp_server/src/lib.rs
@@ -31,6 +31,8 @@ mod config;
 mod world;
 mod diagnostics;
 
+use serde::de::DeserializeOwned;
+
 pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;
 pub use crate::{
     caps::server_capabilities,
@@ -38,3 +40,9 @@ pub use crate::{
     main_loop::LspError,
     main_loop::{main_loop, show_message},
 };
+
+pub fn from_json<T: DeserializeOwned>(what: &'static str, json: serde_json::Value) -> Result<T> {
+    let res = T::deserialize(&json)
+        .map_err(|e| format!("Failed to deserialize {}: {}; {}", what, e, json))?;
+    Ok(res)
+}
diff --git a/crates/ra_lsp_server/src/main.rs b/crates/ra_lsp_server/src/main.rs
index 3879eeff2..c8a017c5c 100644
--- a/crates/ra_lsp_server/src/main.rs
+++ b/crates/ra_lsp_server/src/main.rs
@@ -1,7 +1,7 @@
 //! `ra_lsp_server` binary
 
 use lsp_server::Connection;
-use ra_lsp_server::{show_message, Result, ServerConfig};
+use ra_lsp_server::{from_json, show_message, Result, ServerConfig};
 use ra_prof;
 
 fn main() -> Result<()> {
@@ -45,7 +45,8 @@ fn run_server() -> Result<()> {
     let server_capabilities = serde_json::to_value(ra_lsp_server::server_capabilities()).unwrap();
 
     let initialize_params = connection.initialize(server_capabilities)?;
-    let initialize_params: lsp_types::InitializeParams = serde_json::from_value(initialize_params)?;
+    let initialize_params =
+        from_json::<lsp_types::InitializeParams>("InitializeParams", initialize_params)?;
 
     if let Some(client_info) = initialize_params.client_info {
         log::info!("Client '{}' {}", client_info.name, client_info.version.unwrap_or_default());
@@ -62,17 +63,13 @@ fn run_server() -> Result<()> {
         .filter(|workspaces| !workspaces.is_empty())
         .unwrap_or_else(|| vec![root]);
 
-    let server_config: ServerConfig = initialize_params
+    let server_config = initialize_params
         .initialization_options
         .and_then(|v| {
-            serde_json::from_value(v)
+            from_json::<ServerConfig>("config", v)
                 .map_err(|e| {
-                    log::error!("failed to deserialize config: {}", e);
-                    show_message(
-                        lsp_types::MessageType::Error,
-                        format!("failed to deserialize config: {}", e),
-                        &connection.sender,
-                    );
+                    log::error!("{}", e);
+                    show_message(lsp_types::MessageType::Error, e.to_string(), &connection.sender);
                 })
                 .ok()
         })
diff --git a/crates/ra_lsp_server/src/main_loop/handlers.rs b/crates/ra_lsp_server/src/main_loop/handlers.rs
index 282f6e8fc..59c86bbfa 100644
--- a/crates/ra_lsp_server/src/main_loop/handlers.rs
+++ b/crates/ra_lsp_server/src/main_loop/handlers.rs
@@ -2,20 +2,21 @@
 //! The majority of requests are fulfilled by calling into the `ra_ide` crate.
 
 use std::{
+    collections::hash_map::Entry,
     fmt::Write as _,
     io::Write as _,
     process::{self, Stdio},
 };
 
-use either::Either;
 use lsp_server::ErrorCode;
 use lsp_types::{
     CallHierarchyIncomingCall, CallHierarchyIncomingCallsParams, CallHierarchyItem,
     CallHierarchyOutgoingCall, CallHierarchyOutgoingCallsParams, CallHierarchyPrepareParams,
-    CodeAction, CodeActionResponse, CodeLens, Command, CompletionItem, Diagnostic,
-    DocumentFormattingParams, DocumentHighlight, DocumentSymbol, FoldingRange, FoldingRangeParams,
-    Hover, HoverContents, Location, MarkupContent, MarkupKind, Position, PrepareRenameResponse,
-    Range, RenameParams, SymbolInformation, TextDocumentIdentifier, TextEdit, WorkspaceEdit,
+    CodeAction, CodeActionOrCommand, CodeActionResponse, CodeLens, Command, CompletionItem,
+    Diagnostic, DocumentFormattingParams, DocumentHighlight, DocumentSymbol, FoldingRange,
+    FoldingRangeParams, Hover, HoverContents, Location, MarkupContent, MarkupKind, Position,
+    PrepareRenameResponse, Range, RenameParams, SymbolInformation, TextDocumentIdentifier,
+    TextEdit, WorkspaceEdit,
 };
 use ra_ide::{
     AssistId, FileId, FilePosition, FileRange, Query, RangeInfo, Runnable, RunnableKind,
@@ -34,6 +35,7 @@ use crate::{
         TryConvWithToVec,
     },
     diagnostics::DiagnosticTask,
+    from_json,
     req::{self, Decoration, InlayHint, InlayHintsParams, InlayKind},
     world::WorldSnapshot,
     LspError, Result,
@@ -685,34 +687,53 @@ pub fn handle_code_action(
         res.push(fix.action.clone());
     }
 
+    let mut groups = FxHashMap::default();
     for assist in world.analysis().assists(FileRange { file_id, range })?.into_iter() {
-        let title = assist.label.clone();
+        let arg = to_value(assist.source_change.try_conv_with(&world)?)?;
+
+        let (command, title, arg) = match assist.group_label {
+            None => ("rust-analyzer.applySourceChange", assist.label.clone(), arg),
+
+            // Group all assists with the same `group_label` into a single CodeAction.
+            Some(group_label) => {
+                match groups.entry(group_label.clone()) {
+                    Entry::Occupied(entry) => {
+                        let idx: usize = *entry.get();
+                        match &mut res[idx] {
+                            CodeActionOrCommand::CodeAction(CodeAction {
+                                command: Some(Command { arguments: Some(arguments), .. }),
+                                ..
+                            }) => match arguments.as_mut_slice() {
+                                [serde_json::Value::Array(arguments)] => arguments.push(arg),
+                                _ => panic!("invalid group"),
+                            },
+                            _ => panic!("invalid group"),
+                        }
+                        continue;
+                    }
+                    Entry::Vacant(entry) => {
+                        entry.insert(res.len());
+                    }
+                }
+                ("rust-analyzer.selectAndApplySourceChange", group_label, to_value(vec![arg])?)
+            }
+        };
 
-        let command = match assist.change_data {
-            Either::Left(change) => Command {
-                title,
-                command: "rust-analyzer.applySourceChange".to_string(),
-                arguments: Some(vec![to_value(change.try_conv_with(&world)?)?]),
-            },
-            Either::Right(changes) => Command {
-                title,
-                command: "rust-analyzer.selectAndApplySourceChange".to_string(),
-                arguments: Some(vec![to_value(
-                    changes
-                        .into_iter()
-                        .map(|change| change.try_conv_with(&world))
-                        .collect::<Result<Vec<_>>>()?,
-                )?]),
-            },
+        let command = Command {
+            title: assist.label.clone(),
+            command: command.to_string(),
+            arguments: Some(vec![arg]),
+        };
+
+        let kind = match assist.id {
+            AssistId("introduce_variable") => Some("refactor.extract.variable".to_string()),
+            AssistId("add_custom_impl") => Some("refactor.rewrite.add_custom_impl".to_string()),
+            _ => None,
         };
 
         let action = CodeAction {
-            title: command.title.clone(),
-            kind: match assist.id {
-                AssistId("introduce_variable") => Some("refactor.extract.variable".to_string()),
-                AssistId("add_custom_impl") => Some("refactor.rewrite.add_custom_impl".to_string()),
-                _ => None,
-            },
+            title,
+            kind,
             diagnostics: None,
             edit: None,
             command: Some(command),
@@ -791,7 +812,7 @@ enum CodeLensResolveData {
 pub fn handle_code_lens_resolve(world: WorldSnapshot, code_lens: CodeLens) -> Result<CodeLens> {
     let _p = profile("handle_code_lens_resolve");
     let data = code_lens.data.unwrap();
-    let resolve = serde_json::from_value(data)?;
+    let resolve = from_json::<Option<CodeLensResolveData>>("CodeLensResolveData", data)?;
     match resolve {
         Some(CodeLensResolveData::Impls(lens_params)) => {
             let locations: Vec<Location> =