internal: Allow OnTypeFormatting to send SnippetTextEdit

But continue to send TextEdit only.

crates/ide/src/typing.rs

@@ -34,6 +34,11 @@ pub(crate) use on_enter::on_enter;
 // Don't forget to add new trigger characters to `server_capabilities` in `caps.rs`.
 pub(crate) const TRIGGER_CHARS: &str = ".=>{";
 
+struct ExtendedTextEdit {
+    edit: TextEdit,
+    is_snippet: bool,
+}
+
 // Feature: On Typing Assists
 //
 // Some features trigger on typing certain characters:
@@ -68,22 +73,27 @@ pub(crate) fn on_char_typed(
         return None;
     }
     let edit = on_char_typed_inner(file, position.offset, char_typed)?;
-    Some(SourceChange::from_text_edit(position.file_id, edit))
+    let mut sc = SourceChange::from_text_edit(position.file_id, edit.edit);
+    sc.is_snippet = edit.is_snippet;
+    Some(sc)
 }
 
 fn on_char_typed_inner(
     file: &Parse<SourceFile>,
     offset: TextSize,
     char_typed: char,
-) -> Option<TextEdit> {
+) -> Option<ExtendedTextEdit> {
+    fn conv(text_edit: Option<TextEdit>) -> Option<ExtendedTextEdit> {
+        Some(ExtendedTextEdit { edit: text_edit?, is_snippet: false })
+    }
     if !stdx::always!(TRIGGER_CHARS.contains(char_typed)) {
         return None;
     }
     match char_typed {
-        '.' => on_dot_typed(&file.tree(), offset),
-        '=' => on_eq_typed(&file.tree(), offset),
-        '>' => on_arrow_typed(&file.tree(), offset),
-        '{' => on_opening_brace_typed(file, offset),
+        '.' => conv(on_dot_typed(&file.tree(), offset)),
+        '=' => conv(on_eq_typed(&file.tree(), offset)),
+        '>' => conv(on_arrow_typed(&file.tree(), offset)),
+        '{' => conv(on_opening_brace_typed(file, offset)),
         _ => unreachable!(),
     }
 }

crates/rust-analyzer/src/handlers.rs

@@ -276,7 +276,7 @@ pub(crate) fn handle_on_enter(
 pub(crate) fn handle_on_type_formatting(
     snap: GlobalStateSnapshot,
     params: lsp_types::DocumentOnTypeFormattingParams,
-) -> Result<Option<Vec<lsp_types::TextEdit>>> {
+) -> Result<Option<Vec<lsp_ext::SnippetTextEdit>>> {
     let _p = profile::span("handle_on_type_formatting");
     let mut position = from_proto::file_position(&snap, params.text_document_position)?;
     let line_index = snap.file_line_index(position.file_id)?;
@@ -306,9 +306,9 @@ pub(crate) fn handle_on_type_formatting(
     };
 
     // This should be a single-file edit
-    let (_, edit) = edit.source_file_edits.into_iter().next().unwrap();
+    let (_, text_edit) = edit.source_file_edits.into_iter().next().unwrap();
 
-    let change = to_proto::text_edit_vec(&line_index, edit);
+    let change = to_proto::snippet_text_edit_vec(&line_index, edit.is_snippet, text_edit);
     Ok(Some(change))
 }
 

crates/rust-analyzer/src/lsp_ext.rs

@@ -4,8 +4,8 @@ use std::{collections::HashMap, path::PathBuf};
 
 use lsp_types::request::Request;
 use lsp_types::{
-    notification::Notification, CodeActionKind, PartialResultParams, Position, Range,
-    TextDocumentIdentifier, WorkDoneProgressParams,
+    notification::Notification, CodeActionKind, DocumentOnTypeFormattingParams,
+    PartialResultParams, Position, Range, TextDocumentIdentifier, WorkDoneProgressParams,
 };
 use serde::{Deserialize, Serialize};
 
@@ -512,6 +512,19 @@ pub enum WorkspaceSymbolSearchKind {
     AllSymbols,
 }
 
+/// The document on type formatting request is sent from the client to
+/// the server to format parts of the document during typing.  This is
+/// almost same as lsp_types::request::OnTypeFormatting, but the
+/// result has SnippetTextEdit in it instead of TextEdit.
+#[derive(Debug)]
+pub enum OnTypeFormatting {}
+
+impl Request for OnTypeFormatting {
+    type Params = DocumentOnTypeFormattingParams;
+    type Result = Option<Vec<SnippetTextEdit>>;
+    const METHOD: &'static str = "textDocument/onTypeFormatting";
+}
+
 #[derive(Debug, Serialize, Deserialize)]
 pub struct CompletionResolveData {
     pub position: lsp_types::TextDocumentPositionParams,

crates/rust-analyzer/src/main_loop.rs

@@ -605,7 +605,7 @@ impl GlobalState {
             .on::<lsp_ext::OpenCargoToml>(handlers::handle_open_cargo_toml)
             .on::<lsp_ext::MoveItem>(handlers::handle_move_item)
             .on::<lsp_ext::WorkspaceSymbol>(handlers::handle_workspace_symbol)
-            .on::<lsp_types::request::OnTypeFormatting>(handlers::handle_on_type_formatting)
+            .on::<lsp_ext::OnTypeFormatting>(handlers::handle_on_type_formatting)
             .on::<lsp_types::request::DocumentSymbolRequest>(handlers::handle_document_symbol)
             .on::<lsp_types::request::GotoDefinition>(handlers::handle_goto_definition)
             .on::<lsp_types::request::GotoDeclaration>(handlers::handle_goto_declaration)

docs/dev/lsp-extensions.md

@@ -1,5 +1,5 @@
 <!---
-lsp_ext.rs hash: 44e8238e4fbd4128
+lsp_ext.rs hash: 2a188defec26cc7c
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this issue:
@@ -47,7 +47,7 @@ If a language client does not know about `rust-analyzer`'s configuration options
 
 **Experimental Client Capability:** `{ "snippetTextEdit": boolean }`
 
-If this capability is set, `WorkspaceEdit`s returned from `codeAction` requests might contain `SnippetTextEdit`s instead of usual `TextEdit`s:
+If this capability is set, `WorkspaceEdit`s returned from `codeAction` requests and `TextEdit`s returned from `textDocument/onTypeFormatting` requests might contain `SnippetTextEdit`s instead of usual `TextEdit`s:
 
 ```typescript
 interface SnippetTextEdit extends TextEdit {
@@ -63,7 +63,7 @@ export interface TextDocumentEdit {
 }
 ```
 
-When applying such code action, the editor should insert snippet, with tab stops and placeholder.
+When applying such code action or text edit, the editor should insert snippet, with tab stops and placeholder.
 At the moment, rust-analyzer guarantees that only a single edit will have `InsertTextFormat.Snippet`.
 
 ### Example