9 files changed, 200 insertions, 119 deletions

diff --git a/crates/ra_assists/src/assist_context.rs b/crates/ra_assists/src/assist_context.rs
index b90bbf8b2..0dcd9df61 100644
--- a/crates/ra_assists/src/assist_context.rs
+++ b/crates/ra_assists/src/assist_context.rs
@@ -208,16 +208,6 @@ impl AssistBuilder {
     pub(crate) fn replace(&mut self, range: TextRange, replace_with: impl Into<String>) {
         self.edit.replace(range, replace_with.into())
     }
-    /// Append specified `text` at the given `offset`
-    pub(crate) fn replace_snippet(
-        &mut self,
-        _cap: SnippetCap,
-        range: TextRange,
-        replace_with: impl Into<String>,
-    ) {
-        self.is_snippet = true;
-        self.edit.replace(range, replace_with.into())
-    }
     pub(crate) fn replace_ast<N: AstNode>(&mut self, old: N, new: N) {
         algo::diff(old.syntax(), new.syntax()).into_text_edit(&mut self.edit)
     }
diff --git a/crates/rust-analyzer/src/diagnostics.rs b/crates/rust-analyzer/src/diagnostics.rs
index 4bdd45a7d..25856c543 100644
--- a/crates/rust-analyzer/src/diagnostics.rs
+++ b/crates/rust-analyzer/src/diagnostics.rs
@@ -3,9 +3,11 @@ pub(crate) mod to_proto;
 
 use std::{collections::HashMap, sync::Arc};
 
-use lsp_types::{CodeActionOrCommand, Diagnostic, Range};
+use lsp_types::{Diagnostic, Range};
 use ra_ide::FileId;
 
+use crate::lsp_ext;
+
 pub type CheckFixes = Arc<HashMap<FileId, Vec<Fix>>>;
 
 #[derive(Debug, Default, Clone)]
@@ -18,13 +20,13 @@ pub struct DiagnosticCollection {
 #[derive(Debug, Clone)]
 pub struct Fix {
     pub range: Range,
-    pub action: CodeActionOrCommand,
+    pub action: lsp_ext::CodeAction,
 }
 
 #[derive(Debug)]
 pub enum DiagnosticTask {
     ClearCheck,
-    AddCheck(FileId, Diagnostic, Vec<CodeActionOrCommand>),
+    AddCheck(FileId, Diagnostic, Vec<lsp_ext::CodeAction>),
     SetNative(FileId, Vec<Diagnostic>),
 }
 
@@ -38,7 +40,7 @@ impl DiagnosticCollection {
         &mut self,
         file_id: FileId,
         diagnostic: Diagnostic,
-        fixes: Vec<CodeActionOrCommand>,
+        fixes: Vec<lsp_ext::CodeAction>,
     ) {
         let diagnostics = self.check.entry(file_id).or_default();
         for existing_diagnostic in diagnostics.iter() {
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
index 076b3cf27..96466b5c9 100644
--- a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_multi_line_fix.snap
@@ -68,9 +68,9 @@ expression: diag
                 kind: Some(
                     "quickfix",
                 ),
-                diagnostics: None,
+                command: None,
                 edit: Some(
-                    WorkspaceEdit {
+                    SnippetWorkspaceEdit {
                         changes: Some(
                             {
                                 "file:///test/src/main.rs": [
@@ -106,8 +106,6 @@ expression: diag
                         document_changes: None,
                     },
                 ),
-                command: None,
-                is_preferred: None,
             },
         ],
     },
diff --git a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
index 69138c15b..8f962277f 100644
--- a/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
+++ b/crates/rust-analyzer/src/diagnostics/snapshots/rust_analyzer__diagnostics__to_proto__tests__snap_rustc_unused_variable.snap
@@ -53,9 +53,9 @@ expression: diag
                 kind: Some(
                     "quickfix",
                 ),
-                diagnostics: None,
+                command: None,
                 edit: Some(
-                    WorkspaceEdit {
+                    SnippetWorkspaceEdit {
                         changes: Some(
                             {
                                 "file:///test/driver/subcommand/repl.rs": [
@@ -78,8 +78,6 @@ expression: diag
                         document_changes: None,
                     },
                 ),
-                command: None,
-                is_preferred: None,
             },
         ],
     },
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index eabf4908f..afea59525 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -7,13 +7,13 @@ use std::{
 };
 
 use lsp_types::{
-    CodeAction, Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag,
-    Location, NumberOrString, Position, Range, TextEdit, Url, WorkspaceEdit,
+    Diagnostic, DiagnosticRelatedInformation, DiagnosticSeverity, DiagnosticTag, Location,
+    NumberOrString, Position, Range, TextEdit, Url,
 };
 use ra_flycheck::{Applicability, DiagnosticLevel, DiagnosticSpan, DiagnosticSpanMacroExpansion};
 use stdx::format_to;
 
-use crate::Result;
+use crate::{lsp_ext, Result};
 
 /// Converts a Rust level string to a LSP severity
 fn map_level_to_severity(val: DiagnosticLevel) -> Option<DiagnosticSeverity> {
@@ -110,7 +110,7 @@ fn is_deprecated(rd: &ra_flycheck::Diagnostic) -> bool {
 
 enum MappedRustChildDiagnostic {
     Related(DiagnosticRelatedInformation),
-    SuggestedFix(CodeAction),
+    SuggestedFix(lsp_ext::CodeAction),
     MessageLine(String),
 }
 
@@ -143,13 +143,15 @@ fn map_rust_child_diagnostic(
             message: rd.message.clone(),
         })
     } else {
-        MappedRustChildDiagnostic::SuggestedFix(CodeAction {
+        MappedRustChildDiagnostic::SuggestedFix(lsp_ext::CodeAction {
             title: rd.message.clone(),
             kind: Some("quickfix".to_string()),
-            diagnostics: None,
-            edit: Some(WorkspaceEdit::new(edit_map)),
+            edit: Some(lsp_ext::SnippetWorkspaceEdit {
+                // FIXME: there's no good reason to use edit_map here....
+                changes: Some(edit_map),
+                document_changes: None,
+            }),
             command: None,
-            is_preferred: None,
         })
     }
 }
@@ -158,7 +160,7 @@ fn map_rust_child_diagnostic(
 pub(crate) struct MappedRustDiagnostic {
     pub location: Location,
     pub diagnostic: Diagnostic,
-    pub fixes: Vec<CodeAction>,
+    pub fixes: Vec<lsp_ext::CodeAction>,
 }
 
 /// Converts a Rust root diagnostic to LSP form
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index 313a8c769..c7a3a6911 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -1,6 +1,6 @@
 //! rust-analyzer extensions to the LSP.
 
-use std::path::PathBuf;
+use std::{collections::HashMap, path::PathBuf};
 
 use lsp_types::request::Request;
 use lsp_types::{Location, Position, Range, TextDocumentIdentifier};
@@ -137,7 +137,7 @@ pub struct Runnable {
 #[serde(rename_all = "camelCase")]
 pub struct SourceChange {
     pub label: String,
-    pub workspace_edit: lsp_types::WorkspaceEdit,
+    pub workspace_edit: SnippetWorkspaceEdit,
     pub cursor_position: Option<lsp_types::TextDocumentPositionParams>,
 }
 
@@ -183,3 +183,52 @@ pub struct SsrParams {
     pub query: String,
     pub parse_only: bool,
 }
+
+pub enum CodeActionRequest {}
+
+impl Request for CodeActionRequest {
+    type Params = lsp_types::CodeActionParams;
+    type Result = Option<Vec<CodeAction>>;
+    const METHOD: &'static str = "textDocument/codeAction";
+}
+
+#[derive(Debug, PartialEq, Clone, Default, Deserialize, Serialize)]
+pub struct CodeAction {
+    pub title: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub kind: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub command: Option<lsp_types::Command>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub edit: Option<SnippetWorkspaceEdit>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetWorkspaceEdit {
+    pub changes: Option<HashMap<lsp_types::Url, Vec<lsp_types::TextEdit>>>,
+    pub document_changes: Option<Vec<SnippetDocumentChangeOperation>>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Deserialize, Serialize)]
+#[serde(untagged, rename_all = "lowercase")]
+pub enum SnippetDocumentChangeOperation {
+    Op(lsp_types::ResourceOp),
+    Edit(SnippetTextDocumentEdit),
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetTextDocumentEdit {
+    pub text_document: lsp_types::VersionedTextDocumentIdentifier,
+    pub edits: Vec<SnippetTextEdit>,
+}
+
+#[derive(Debug, Eq, PartialEq, Clone, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnippetTextEdit {
+    pub range: Range,
+    pub new_text: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub insert_text_format: Option<lsp_types::InsertTextFormat>,
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 15e5bb354..87795fffb 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -518,6 +518,7 @@ fn on_request(
         .on::<lsp_ext::ParentModule>(handlers::handle_parent_module)?
         .on::<lsp_ext::Runnables>(handlers::handle_runnables)?
         .on::<lsp_ext::InlayHints>(handlers::handle_inlay_hints)?
+        .on::<lsp_ext::CodeActionRequest>(handlers::handle_code_action)?
         .on::<lsp_types::request::OnTypeFormatting>(handlers::handle_on_type_formatting)?
         .on::<lsp_types::request::DocumentSymbolRequest>(handlers::handle_document_symbol)?
         .on::<lsp_types::request::WorkspaceSymbol>(handlers::handle_workspace_symbol)?
@@ -525,7 +526,6 @@ fn on_request(
         .on::<lsp_types::request::GotoImplementation>(handlers::handle_goto_implementation)?
         .on::<lsp_types::request::GotoTypeDefinition>(handlers::handle_goto_type_definition)?
         .on::<lsp_types::request::Completion>(handlers::handle_completion)?
-        .on::<lsp_types::request::CodeActionRequest>(handlers::handle_code_action)?
         .on::<lsp_types::request::CodeLensRequest>(handlers::handle_code_lens)?
         .on::<lsp_types::request::CodeLensResolve>(handlers::handle_code_lens_resolve)?
         .on::<lsp_types::request::FoldingRangeRequest>(handlers::handle_folding_range)?
diff --git a/crates/rust-analyzer/src/main_loop/handlers.rs b/crates/rust-analyzer/src/main_loop/handlers.rs
index 13ae061fa..4ff8fa69e 100644
--- a/crates/rust-analyzer/src/main_loop/handlers.rs
+++ b/crates/rust-analyzer/src/main_loop/handlers.rs
@@ -11,12 +11,11 @@ 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, SemanticTokensParams, SemanticTokensRangeParams,
-    SemanticTokensRangeResult, SemanticTokensResult, SymbolInformation, TextDocumentIdentifier,
-    TextEdit, Url, WorkspaceEdit,
+    CodeLens, Command, CompletionItem, Diagnostic, DocumentFormattingParams, DocumentHighlight,
+    DocumentSymbol, FoldingRange, FoldingRangeParams, Hover, HoverContents, Location,
+    MarkupContent, MarkupKind, Position, PrepareRenameResponse, Range, RenameParams,
+    SemanticTokensParams, SemanticTokensRangeParams, SemanticTokensRangeResult,
+    SemanticTokensResult, SymbolInformation, TextDocumentIdentifier, TextEdit, Url, WorkspaceEdit,
 };
 use ra_ide::{
     Assist, FileId, FilePosition, FileRange, Query, RangeInfo, Runnable, RunnableKind, SearchScope,
@@ -585,9 +584,8 @@ pub fn handle_rename(world: WorldSnapshot, params: RenameParams) -> Result<Optio
         None => return Ok(None),
         Some(it) => it.info,
     };
-
-    let source_change = to_proto::source_change(&world, source_change)?;
-    Ok(Some(source_change.workspace_edit))
+    let workspace_edit = to_proto::workspace_edit(&world, source_change)?;
+    Ok(Some(workspace_edit))
 }
 
 pub fn handle_references(
@@ -696,14 +694,21 @@ pub fn handle_formatting(
 pub fn handle_code_action(
     world: WorldSnapshot,
     params: lsp_types::CodeActionParams,
-) -> Result<Option<CodeActionResponse>> {
+) -> Result<Option<Vec<lsp_ext::CodeAction>>> {
     let _p = profile("handle_code_action");
+    // We intentionally don't support command-based actions, as those either
+    // requires custom client-code anyway, or requires server-initiated edits.
+    // Server initiated edits break causality, so we avoid those as well.
+    if !world.config.client_caps.code_action_literals {
+        return Ok(None);
+    }
+
     let file_id = from_proto::file_id(&world, &params.text_document.uri)?;
     let line_index = world.analysis().file_line_index(file_id)?;
     let range = from_proto::text_range(&line_index, params.range);
 
     let diagnostics = world.analysis().diagnostics(file_id)?;
-    let mut res = CodeActionResponse::default();
+    let mut res: Vec<lsp_ext::CodeAction> = Vec::new();
 
     let fixes_from_diagnostics = diagnostics
         .into_iter()
@@ -713,22 +718,9 @@ pub fn handle_code_action(
 
     for source_edit in fixes_from_diagnostics {
         let title = source_edit.label.clone();
-        let edit = to_proto::source_change(&world, source_edit)?;
-
-        let command = Command {
-            title,
-            command: "rust-analyzer.applySourceChange".to_string(),
-            arguments: Some(vec![to_value(edit).unwrap()]),
-        };
-        let action = CodeAction {
-            title: command.title.clone(),
-            kind: None,
-            diagnostics: None,
-            edit: None,
-            command: Some(command),
-            is_preferred: None,
-        };
-        res.push(action.into());
+        let edit = to_proto::snippet_workspace_edit(&world, source_edit)?;
+        let action = lsp_ext::CodeAction { title, kind: None, edit: Some(edit), command: None };
+        res.push(action);
     }
 
     for fix in world.check_fixes.get(&file_id).into_iter().flatten() {
@@ -748,8 +740,13 @@ pub fn handle_code_action(
                 .entry(label.to_owned())
                 .or_insert_with(|| {
                     let idx = res.len();
-                    let dummy = Command::new(String::new(), String::new(), None);
-                    res.push(dummy.into());
+                    let dummy = lsp_ext::CodeAction {
+                        title: String::new(),
+                        kind: None,
+                        command: None,
+                        edit: None,
+                    };
+                    res.push(dummy);
                     (idx, Vec::new())
                 })
                 .1
@@ -777,35 +774,10 @@ pub fn handle_code_action(
                 command: "rust-analyzer.selectAndApplySourceChange".to_string(),
                 arguments: Some(vec![serde_json::Value::Array(arguments)]),
             });
-            res[idx] = CodeAction {
-                title,
-                kind: None,
-                diagnostics: None,
-                edit: None,
-                command,
-                is_preferred: None,
-            }
-            .into();
+            res[idx] = lsp_ext::CodeAction { title, kind: None, edit: None, command };
         }
     }
 
-    // If the client only supports commands then filter the list
-    // and remove and actions that depend on edits.
-    if !world.config.client_caps.code_action_literals {
-        // FIXME: use drain_filter once it hits stable.
-        res = res
-            .into_iter()
-            .filter_map(|it| match it {
-                cmd @ lsp_types::CodeActionOrCommand::Command(_) => Some(cmd),
-                lsp_types::CodeActionOrCommand::CodeAction(action) => match action.command {
-                    Some(cmd) if action.edit.is_none() => {
-                        Some(lsp_types::CodeActionOrCommand::Command(cmd))
-                    }
-                    _ => None,
-                },
-            })
-            .collect();
-    }
     Ok(Some(res))
 }
 
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index a8e2e535f..2b1a3378f 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -112,6 +112,22 @@ pub(crate) fn text_edit(
     lsp_types::TextEdit { range, new_text }
 }
 
+pub(crate) fn snippet_text_edit(
+    line_index: &LineIndex,
+    line_endings: LineEndings,
+    is_snippet: bool,
+    indel: Indel,
+) -> lsp_ext::SnippetTextEdit {
+    let text_edit = text_edit(line_index, line_endings, indel);
+    let insert_text_format =
+        if is_snippet { Some(lsp_types::InsertTextFormat::Snippet) } else { None };
+    lsp_ext::SnippetTextEdit {
+        range: text_edit.range,
+        new_text: text_edit.new_text,
+        insert_text_format,
+    }
+}
+
 pub(crate) fn text_edit_vec(
     line_index: &LineIndex,
     line_endings: LineEndings,
@@ -441,10 +457,11 @@ pub(crate) fn goto_definition_response(
     }
 }
 
-pub(crate) fn text_document_edit(
+pub(crate) fn snippet_text_document_edit(
     world: &WorldSnapshot,
+    is_snippet: bool,
     source_file_edit: SourceFileEdit,
-) -> Result<lsp_types::TextDocumentEdit> {
+) -> Result<lsp_ext::SnippetTextDocumentEdit> {
     let text_document = versioned_text_document_identifier(world, source_file_edit.file_id, None)?;
     let line_index = world.analysis().file_line_index(source_file_edit.file_id)?;
     let line_endings = world.file_line_endings(source_file_edit.file_id);
@@ -452,9 +469,9 @@ pub(crate) fn text_document_edit(
         .edit
         .as_indels()
         .iter()
-        .map(|it| text_edit(&line_index, line_endings, it.clone()))
+        .map(|it| snippet_text_edit(&line_index, line_endings, is_snippet, it.clone()))
         .collect();
-    Ok(lsp_types::TextDocumentEdit { text_document, edits })
+    Ok(lsp_ext::SnippetTextDocumentEdit { text_document, edits })
 }
 
 pub(crate) fn resource_op(
@@ -500,20 +517,70 @@ pub(crate) fn source_change(
             })
         }
     };
-    let mut document_changes: Vec<lsp_types::DocumentChangeOperation> = Vec::new();
+    let label = source_change.label.clone();
+    let workspace_edit = self::snippet_workspace_edit(world, source_change)?;
+    Ok(lsp_ext::SourceChange { label, workspace_edit, cursor_position })
+}
+
+pub(crate) fn snippet_workspace_edit(
+    world: &WorldSnapshot,
+    source_change: SourceChange,
+) -> Result<lsp_ext::SnippetWorkspaceEdit> {
+    let mut document_changes: Vec<lsp_ext::SnippetDocumentChangeOperation> = Vec::new();
     for op in source_change.file_system_edits {
         let op = resource_op(&world, op)?;
-        document_changes.push(lsp_types::DocumentChangeOperation::Op(op));
+        document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Op(op));
     }
     for edit in source_change.source_file_edits {
-        let edit = text_document_edit(&world, edit)?;
-        document_changes.push(lsp_types::DocumentChangeOperation::Edit(edit));
+        let edit = snippet_text_document_edit(&world, source_change.is_snippet, edit)?;
+        document_changes.push(lsp_ext::SnippetDocumentChangeOperation::Edit(edit));
+    }
+    let workspace_edit =
+        lsp_ext::SnippetWorkspaceEdit { changes: None, document_changes: Some(document_changes) };
+    Ok(workspace_edit)
+}
+
+pub(crate) fn workspace_edit(
+    world: &WorldSnapshot,
+    source_change: SourceChange,
+) -> Result<lsp_types::WorkspaceEdit> {
+    assert!(!source_change.is_snippet);
+    snippet_workspace_edit(world, source_change).map(|it| it.into())
+}
+
+impl From<lsp_ext::SnippetWorkspaceEdit> for lsp_types::WorkspaceEdit {
+    fn from(snippet_workspace_edit: lsp_ext::SnippetWorkspaceEdit) -> lsp_types::WorkspaceEdit {
+        lsp_types::WorkspaceEdit {
+            changes: None,
+            document_changes: snippet_workspace_edit.document_changes.map(|changes| {
+                lsp_types::DocumentChanges::Operations(
+                    changes
+                        .into_iter()
+                        .map(|change| match change {
+                            lsp_ext::SnippetDocumentChangeOperation::Op(op) => {
+                                lsp_types::DocumentChangeOperation::Op(op)
+                            }
+                            lsp_ext::SnippetDocumentChangeOperation::Edit(edit) => {
+                                lsp_types::DocumentChangeOperation::Edit(
+                                    lsp_types::TextDocumentEdit {
+                                        text_document: edit.text_document,
+                                        edits: edit
+                                            .edits
+                                            .into_iter()
+                                            .map(|edit| lsp_types::TextEdit {
+                                                range: edit.range,
+                                                new_text: edit.new_text,
+                                            })
+                                            .collect(),
+                                    },
+                                )
+                            }
+                        })
+                        .collect(),
+                )
+            }),
+        }
     }
-    let workspace_edit = lsp_types::WorkspaceEdit {
-        changes: None,
-        document_changes: Some(lsp_types::DocumentChanges::Operations(document_changes)),
-    };
-    Ok(lsp_ext::SourceChange { label: source_change.label, workspace_edit, cursor_position })
 }
 
 pub fn call_hierarchy_item(
@@ -571,22 +638,25 @@ fn main() <fold>{
     }
 }
 
-pub(crate) fn code_action(world: &WorldSnapshot, assist: Assist) -> Result<lsp_types::CodeAction> {
-    let source_change = source_change(&world, assist.source_change)?;
-    let arg = serde_json::to_value(source_change)?;
-    let title = assist.label;
-    let command = lsp_types::Command {
-        title: title.clone(),
-        command: "rust-analyzer.applySourceChange".to_string(),
-        arguments: Some(vec![arg]),
-    };
+pub(crate) fn code_action(world: &WorldSnapshot, assist: Assist) -> Result<lsp_ext::CodeAction> {
+    let res = if assist.source_change.is_snippet {
+        lsp_ext::CodeAction {
+            title: assist.label,
+            kind: Some(String::new()),
+            edit: Some(snippet_workspace_edit(world, assist.source_change)?),
+            command: None,
+        }
+    } else {
+        let source_change = source_change(&world, assist.source_change)?;
+        let arg = serde_json::to_value(source_change)?;
+        let title = assist.label;
+        let command = lsp_types::Command {
+            title: title.clone(),
+            command: "rust-analyzer.applySourceChange".to_string(),
+            arguments: Some(vec![arg]),
+        };
 
-    Ok(lsp_types::CodeAction {
-        title,
-        kind: Some(String::new()),
-        diagnostics: None,
-        edit: None,
-        command: Some(command),
-        is_preferred: None,
-    })
+        lsp_ext::CodeAction { title, kind: Some(String::new()), edit: None, command: Some(command) }
+    };
+    Ok(res)
 }