Show deprecation message when using legacy snippets

packages/cursorless-engine/src/actions/snippetsLegacy/InsertSnippetLegacy.ts

@@ -21,6 +21,7 @@ import {
   findMatchingSnippetDefinitionStrict,
   transformSnippetVariables,
 } from "../snippetsLegacy/snippet";
+import { showLegacySnippetsNotification } from "./legacySnippetsNotification";
 import { textFormatters, type TextFormatterName } from "./textFormatters";
 
 export default class InsertSnippetLegacy {
@@ -95,6 +96,8 @@ export default class InsertSnippetLegacy {
     destinations: Destination[],
     snippetDescription: NamedInsertSnippetArg,
   ): Promise<ActionReturnValue> {
+    showLegacySnippetsNotification();
+
     const editor = ide().getEditableTextEditor(
       ensureSingleEditor(destinations),
     );

packages/cursorless-engine/src/actions/snippetsLegacy/WrapWithSnippetLegacy.ts

@@ -14,6 +14,7 @@ import {
   findMatchingSnippetDefinitionStrict,
   transformSnippetVariables,
 } from "../snippetsLegacy/snippet";
+import { showLegacySnippetsNotification } from "./legacySnippetsNotification";
 
 export default class WrapWithSnippetLegacy {
   private snippetParser = new SnippetParser();
@@ -81,6 +82,8 @@ export default class WrapWithSnippetLegacy {
     targets: Target[],
     snippetDescription: NamedWrapWithSnippetArg,
   ): Promise<ActionReturnValue> {
+    showLegacySnippetsNotification();
+
     const editor = ide().getEditableTextEditor(ensureSingleEditor(targets));
 
     const body = this.getBody(snippetDescription, targets);

packages/cursorless-engine/src/actions/snippetsLegacy/legacySnippetsNotification.ts

@@ -0,0 +1,19 @@
+import { showWarning } from "@cursorless/common";
+import { ide } from "../../singletons/ide.singleton";
+
+// Show only once per vscode instance
+let wasShown = false;
+
+export function showLegacySnippetsNotification() {
+  if (wasShown) {
+    return;
+  }
+
+  void showWarning(
+    ide().messages,
+    "legacySnippets",
+    "Talon community snippets are now fully supported in Cursorless! Cursorless's experimental snippets are now deprecated, but in most cases we can help you migrate automatically. Update cursorless-talon and say 'cursorless migrate snippets'.",
+  );
+
+  wasShown = true;
+}