(for now) don't disallow but warn and collect extensions with bogous resolveCompletionItem behaviour (microsoft#183426)

re microsoft#183092

Author: jrieken

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

@@ -1033,12 +1033,19 @@ class CompletionsAdapter {
 			return undefined;
 		}
 
-		return this._convertCompletionItem({
+		const enforcedResolvedItem = {
 			...item,
 			documentation: resolvedItem.documentation,
 			detail: resolvedItem.detail,
 			additionalTextEdits: resolvedItem.additionalTextEdits
-		}, id);
+		};
+
+		if (item.insertText !== resolvedItem.insertText) {
+			this._apiDeprecation.report('CompletionItem.insertText', this._extension, 'extension MAY NOT change \'insertText\' of a CompletionItem during resolve');
+			enforcedResolvedItem.insertText = resolvedItem.insertText;
+		}
+
+		return this._convertCompletionItem(enforcedResolvedItem, id);
 	}
 
 	releaseCompletionItems(id: number): any {