if needed , read clipboard inside MainThreadEditors#insertText, https://github.com/microsoft/vscode/issues/98497

src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts

@@ -29,6 +29,7 @@ import { ITextFileService } from 'vs/workbench/services/textfile/common/textfile
 import { IWorkbenchEnvironmentService } from 'vs/workbench/services/environment/common/environmentService';
 import { IWorkingCopyFileService } from 'vs/workbench/services/workingCopy/common/workingCopyFileService';
 import { IUriIdentityService } from 'vs/workbench/services/uriIdentity/common/uriIdentity';
+import { IClipboardService } from 'vs/platform/clipboard/common/clipboardService';
 
 namespace delta {
 
@@ -331,6 +332,7 @@ export class MainThreadDocumentsAndEditors {
 		@IWorkbenchEnvironmentService environmentService: IWorkbenchEnvironmentService,
 		@IWorkingCopyFileService workingCopyFileService: IWorkingCopyFileService,
 		@IUriIdentityService uriIdentityService: IUriIdentityService,
+		@IClipboardService private readonly _clipboardService: IClipboardService,
 	) {
 		this._proxy = extHostContext.getProxy(ExtHostContext.ExtHostDocumentsAndEditors);
 
@@ -365,7 +367,7 @@ export class MainThreadDocumentsAndEditors {
 		// added editors
 		for (const apiEditor of delta.addedEditors) {
 			const mainThreadEditor = new MainThreadTextEditor(apiEditor.id, apiEditor.editor.getModel(),
-				apiEditor.editor, { onGainedFocus() { }, onLostFocus() { } }, this._modelService);
+				apiEditor.editor, { onGainedFocus() { }, onLostFocus() { } }, this._modelService, this._clipboardService);
 
 			this._textEditors.set(apiEditor.id, mainThreadEditor);
 			addedEditors.push(mainThreadEditor);

src/vs/workbench/api/browser/mainThreadEditor.ts

@@ -17,6 +17,8 @@ import { IApplyEditsOptions, IEditorPropertiesChangeData, IResolvedTextEditorCon
 import { IEditorPane } from 'vs/workbench/common/editor';
 import { withNullAsUndefined } from 'vs/base/common/types';
 import { equals } from 'vs/base/common/arrays';
+import { CodeEditorStateFlag, EditorState } from 'vs/editor/browser/core/editorState';
+import { IClipboardService } from 'vs/platform/clipboard/common/clipboardService';
 
 export interface IFocusTracker {
 	onGainedFocus(): void;
@@ -159,6 +161,7 @@ export class MainThreadTextEditor {
 	private readonly _id: string;
 	private _model: ITextModel;
 	private readonly _modelService: IModelService;
+	private readonly _clipboardService: IClipboardService;
 	private readonly _modelListeners = new DisposableStore();
 	private _codeEditor: ICodeEditor | null;
 	private readonly _focusTracker: IFocusTracker;
@@ -172,7 +175,8 @@ export class MainThreadTextEditor {
 		model: ITextModel,
 		codeEditor: ICodeEditor,
 		focusTracker: IFocusTracker,
-		modelService: IModelService
+		modelService: IModelService,
+		clipboardService: IClipboardService,
 	) {
 		this._id = id;
 		this._model = model;
@@ -180,6 +184,7 @@ export class MainThreadTextEditor {
 		this._properties = null;
 		this._focusTracker = focusTracker;
 		this._modelService = modelService;
+		this._clipboardService = clipboardService;
 
 		this._onPropertiesChanged = new Emitter<IEditorPropertiesChangeData>();
 
@@ -454,12 +459,23 @@ export class MainThreadTextEditor {
 		return true;
 	}
 
-	insertSnippet(template: string, ranges: readonly IRange[], opts: IUndoStopOptions) {
+	async insertSnippet(template: string, ranges: readonly IRange[], opts: IUndoStopOptions) {
 
-		if (!this._codeEditor) {
+		if (!this._codeEditor || !this._codeEditor.hasModel()) {
 			return false;
 		}
 
+		// check if clipboard is required and only iff read it (async)
+		let clipboardText: string | undefined;
+		const needsTemplate = SnippetController2.guessNeedsClipboard(template);
+		if (needsTemplate) {
+			const state = new EditorState(this._codeEditor, CodeEditorStateFlag.Value | CodeEditorStateFlag.Position);
+			clipboardText = await this._clipboardService.readText();
+			if (!state.validate(this._codeEditor)) {
+				return false;
+			}
+		}
+
 		const snippetController = SnippetController2.get(this._codeEditor);
 
 		// // cancel previous snippet mode
@@ -471,7 +487,11 @@ export class MainThreadTextEditor {
 		this._codeEditor.focus();
 
 		// make modifications
-		snippetController.insert(template, { overwriteBefore: 0, overwriteAfter: 0, undoStopBefore: opts.undoStopBefore, undoStopAfter: opts.undoStopAfter });
+		snippetController.insert(template, {
+			overwriteBefore: 0, overwriteAfter: 0,
+			undoStopBefore: opts.undoStopBefore, undoStopAfter: opts.undoStopAfter,
+			clipboardText
+		});
 
 		return true;
 	}