only check true edit progress chunks against the live flag, preview must diff against the right, ad-hoc model (microsoft#196561)

fixes microsoft#196047

Author: jrieken

src/vs/workbench/api/common/extHostInlineChat.ts

@@ -156,7 +156,7 @@ export class ExtHostInteractiveEditor implements ExtHostInlineChatShape {
 		let done = false;
 		const progress: vscode.Progress<vscode.InteractiveEditorProgressItem> = {
 			report: async value => {
-				if (!request.live) {
+				if (!request.live && value.edits?.length) {
 					throw new Error('Progress reporting is only supported for live sessions');
 				}
 				if (done || token.isCancellationRequested) {

src/vs/workbench/contrib/inlineChat/browser/inlineChatWidget.ts

@@ -667,19 +667,20 @@ export class InlineChatWidget {
 
 	async showEditsPreview(textModel0: ITextModel, textModelN: ITextModel, allEdits: ISingleEditOperation[][]) {
 
-		const diff = await this._editorWorkerService.computeDiff(textModel0.uri, textModelN.uri, { ignoreTrimWhitespace: false, maxComputationTimeMs: 5000, computeMoves: false }, 'advanced');
-		if (!diff || diff.changes.length === 0) {
-			this.hideEditsPreview();
-			return;
-		}
-
 		this._elements.previewDiff.classList.remove('hidden');
 
 		const languageSelection: ILanguageSelection = { languageId: textModel0.getLanguageId(), onDidChange: Event.None };
 		const modified = this._modelService.createModel(createTextBufferFactoryFromSnapshot(textModel0.createSnapshot()), languageSelection, undefined, true);
 		for (const edits of allEdits) {
 			modified.applyEdits(edits, false);
 		}
+
+		const diff = await this._editorWorkerService.computeDiff(textModel0.uri, modified.uri, { ignoreTrimWhitespace: false, maxComputationTimeMs: 5000, computeMoves: false }, 'advanced');
+		if (!diff || diff.changes.length === 0) {
+			this.hideEditsPreview();
+			return;
+		}
+
 		this._previewDiffEditor.value.setModel({ original: textModel0, modified });
 
 		// joined ranges