When inserting a nested snippet into an existing snippet there is no need to merge them.

This helps with choice completions and enables to go back to an accepted choice element to get prompted again

Author: jrieken

src/vs/editor/contrib/snippet/browser/snippetController2.ts

@@ -145,7 +145,7 @@ export class SnippetController2 implements IEditorContribution {
 					}
 
 					const info = model.getWordUntilPosition(position);
-					const isDefaultOption = info.word === activeChoice.options[0].value;
+					const isAnyOfOptions = Boolean(activeChoice.options.find(o => o.value === info.word));
 					const suggestions: CompletionItem[] = [];
 					for (let i = 0; i < activeChoice.options.length; i++) {
 						const option = activeChoice.options[i];
@@ -155,7 +155,7 @@ export class SnippetController2 implements IEditorContribution {
 							insertText: option.value,
 							sortText: 'a'.repeat(i + 1),
 							range: new Range(position.lineNumber, info.startColumn, position.lineNumber, info.endColumn),
-							filterText: isDefaultOption ? `${info.word}_${option.value}` : option.value,
+							filterText: isAnyOfOptions ? `${info.word}_${option.value}` : undefined,
 							command: { id: 'jumpToNextSnippetPlaceholder', title: localize('next', 'Go to next placeholder...') }
 						});
 					}

src/vs/editor/contrib/snippet/browser/snippetSession.ts

@@ -207,6 +207,11 @@ export class OneSnippet {
 		return this._snippet.placeholders.length > 0;
 	}
 
+	get isTrivialSnippet(): boolean {
+		return this._snippet.placeholders.length === 0
+			|| (this._snippet.placeholders.length === 1 && this._snippet.placeholders[0].isFinalTabstop);
+	}
+
 	computePossibleSelections() {
 		const result = new Map<number, Range[]>();
 		for (const placeholdersWithEqualIndex of this._placeholderGroups) {
@@ -561,18 +566,21 @@ export class SnippetSession {
 				snippets[idx].initialize(undoEdits[idx].textChange);
 			}
 
-			for (const snippet of this._snippets) {
-				snippet.merge(snippets);
+			// Trivial snippets have no placeholder or are just the final placeholder. That means they
+			// are just text insertions and we don't need to merge the nested snippet into the existing
+			// snippet
+			const isTrivialSnippet = snippets[0].isTrivialSnippet;
+			if (!isTrivialSnippet) {
+				for (const snippet of this._snippets) {
+					snippet.merge(snippets);
+				}
+				console.assert(snippets.length === 0);
 			}
-			console.assert(snippets.length === 0);
 
-			if (this._snippets[0].hasPlaceholder) {
+			if (this._snippets[0].hasPlaceholder && !isTrivialSnippet) {
 				return this._move(undefined);
 			} else {
-				return (
-					undoEdits
-						.map(edit => Selection.fromPositions(edit.range.getEndPosition()))
-				);
+				return undoEdits.map(edit => Selection.fromPositions(edit.range.getEndPosition()));
 			}
 		});
 	}

src/vs/editor/contrib/snippet/test/browser/snippetController2.test.ts

@@ -165,6 +165,21 @@ suite('SnippetController2', function () {
 		// assertContextKeys(contextKeys, false, false, false);
 	});
 
+	test('insert, nested trivial snippet', function () {
+		const ctrl = instaService.createInstance(SnippetController2, editor);
+		ctrl.insert('${1:foo}bar$0');
+		assertContextKeys(contextKeys, true, false, true);
+		assertSelections(editor, new Selection(1, 1, 1, 4), new Selection(2, 5, 2, 8));
+
+		ctrl.insert('FOO$0');
+		assertSelections(editor, new Selection(1, 4, 1, 4), new Selection(2, 8, 2, 8));
+		assertContextKeys(contextKeys, true, false, true);
+
+		ctrl.next();
+		assertSelections(editor, new Selection(1, 7, 1, 7), new Selection(2, 11, 2, 11));
+		assertContextKeys(contextKeys, false, false, false);
+	});
+
 	test('insert, nested snippet', function () {
 		const ctrl = instaService.createInstance(SnippetController2, editor);
 		ctrl.insert('${1:foobar}$0');