Add LSP request and response snippet

private/buf/buflsp/completion.go

@@ -444,6 +444,7 @@ func completionItemsForDef(ctx context.Context, file *file, declPath []ast.DeclA
 						tokenSpan,
 						offset,
 					),
+					rpcRequestResponseSnippetCompletionItem(parentDef, tokenSpan),
 				)
 			}
 		} else if showReturnKeyword {
@@ -867,6 +868,50 @@ func keywordToCompletionItem(
 	}
 }
 
+// rpcRequestResponseSnippetCompletionItem returns a completion item for the common RPC pattern.
+// This generates an RPC method declaration with Request/Response message types.
+func rpcRequestResponseSnippetCompletionItem(
+	parentDef ast.DeclDef,
+	tokenSpan source.Span,
+) iter.Seq[protocol.CompletionItem] {
+	return func(yield func(protocol.CompletionItem) bool) {
+		// Create expanded span from cursor (offset) to end of service
+		serviceEndOffset := parentDef.Span().End
+		expandedSpan := source.Span{
+			File:  tokenSpan.File,
+			Start: tokenSpan.End,
+			End:   serviceEndOffset,
+		}
+		body := expandedSpan.Text()
+
+		// The snippet uses ${1:Name} for linked placeholders.
+		// Because everything is in one TextEdit, placeholders work across RPC and messages.
+		var sb strings.Builder
+		sb.WriteString("rpc ${1:Name}(${1:Name}Request) returns (${1:Name}Response);")
+		sb.WriteString(body)
+		sb.WriteString("\n\nmessage ${1:Name}Request {}\n\nmessage ${1:Name}Response {}")
+
+		yield(protocol.CompletionItem{
+			Label:            "rpc Name(NameRequest) returns (NameResponse)",
+			Kind:             protocol.CompletionItemKindSnippet,
+			InsertTextFormat: protocol.InsertTextFormatSnippet,
+			InsertTextMode:   protocol.InsertTextModeAsIs,
+			Detail:           "Insert RPC method with Request and Response messages",
+			Documentation:    "Creates an RPC method declaration and corresponding Request/Response message types",
+			TextEdit: &protocol.TextEdit{
+				Range:   reportSpanToProtocolRange(tokenSpan),
+				NewText: sb.String(),
+			},
+			AdditionalTextEdits: []protocol.TextEdit{
+				{
+					Range:   reportSpanToProtocolRange(expandedSpan),
+					NewText: "", // Delete from cursor to end of service
+				},
+			},
+		})
+	}
+}
+
 // typeReferencesToCompletionItems returns completion items for user-defined types (messages, enums, etc).
 func typeReferencesToCompletionItems(
 	current *file,