fix(testing/unstable): use the correct function frame in inline snapshot

testing/unstable_snapshot.ts

@@ -19,7 +19,15 @@ import {
  * @experimental **UNSTABLE**: New API, yet to be vetted.
  */
 export interface InlineSnapshotOptions<T = unknown>
-  extends Pick<SnapshotOptions<T>, "msg" | "serializer"> {}
+  extends Pick<SnapshotOptions<T>, "msg" | "serializer"> {
+  /**
+   * Function frame to start backtrace from.
+   * The source code location to modify will be decided from the stack that comes after this function.
+   *
+   * This is only relevant if you are wrapping the call to {@linkcode assertInlineSnapshot}.
+   */
+  frame?: typeof assertInlineSnapshot;
+}
 
 interface ErrorLocation {
   lineNumber: number;
@@ -169,6 +177,10 @@ globalThis.addEventListener("unload", () => {
  *
  * Type parameter can be specified to ensure values under comparison have the same type.
  *
+ * This function discovers the caller's source location by doing a stacktrace.
+ * If you wraps this function, make sure to specifiy the correct frame location in
+ * {@linkcode InlineSnapshotOptions.frame}.
+ *
  * @experimental **UNSTABLE**: New API, yet to be vetted.
  *
  * @example Usage
@@ -255,7 +267,11 @@ export function assertInlineSnapshot(
         };
       };
       // Capture the stack that comes after this function.
-      Error.captureStackTrace(stackCatcher, assertInlineSnapshot);
+      Error.captureStackTrace(
+        stackCatcher,
+        // Start backtrace from this frame, otherwise the call location will be wrong.
+        options.frame ?? assertInlineSnapshot,
+      );
       // Forcibly access the stack, and note it down
       const request = stackCatcher.stack;
       if (request !== null) {
@@ -303,12 +319,14 @@ export function createAssertInlineSnapshot<T>(
   options: InlineSnapshotOptions<T>,
   baseAssertSnapshot: typeof assertInlineSnapshot = assertInlineSnapshot,
 ): typeof assertInlineSnapshot {
-  return function (
+  return function frame(
     actual: T,
     expectedSnapshot: string,
     messageOrOptions?: string | InlineSnapshotOptions<T>,
   ) {
     const mergedOptions: InlineSnapshotOptions<T> = {
+      // Ordering matters here to allow outer options overriding frame.
+      frame,
       ...options,
       ...(typeof messageOrOptions === "string"
         ? { msg: messageOrOptions }

testing/unstable_snapshot_test.ts

@@ -151,7 +151,7 @@ Deno.test("assertInlineSnapshot() counts lines and columns like V8", async () =>
     await Deno.writeTextFile(
       countTestFile,
       `import { assertInlineSnapshot } from "${SNAPSHOT_MODULE_URL}";
- \n \r \n\r \r\n \u2028 \u2029 
+ \n \r \n\r \r\n \u2028 \u2029\u0020
 Deno.test("format", async () => {
   /* 🐈‍⬛🇦🇶 */ assertInlineSnapshot( "hello world", "" );
 });`,
@@ -174,7 +174,7 @@ Deno.test("format", async () => {
     assertEquals(
       await Deno.readTextFile(countTestFile),
       `import { assertInlineSnapshot } from "${SNAPSHOT_MODULE_URL}";
- \n \r \n\r \r\n \u2028 \u2029 
+ \n \r \n\r \r\n \u2028 \u2029\u0020
 Deno.test("format", async () => {
   /* 🐈‍⬛🇦🇶 */ assertInlineSnapshot( "hello world", \`"hello world"\` );
 });`,
@@ -193,3 +193,49 @@ Deno.test("createAssertInlineSnapshot()", () => {
     `This green text has had its colors stripped`,
   );
 });
+
+Deno.test("createAssertInlineSnapshot() writes to the correct location", async () => {
+  if (!LINT_SUPPORTED) return;
+
+  const tempDir = await Deno.makeTempDir();
+  const testFile = join(tempDir, "create_test.ts");
+  try {
+    await Deno.writeTextFile(
+      testFile,
+      `import { createAssertInlineSnapshot } from "${SNAPSHOT_MODULE_URL}";
+
+const assertInlineSnapshot = createAssertInlineSnapshot({});
+
+Deno.test("format", () => {
+  assertInlineSnapshot( "hello world", "" );
+});`,
+    );
+
+    const command = new Deno.Command(Deno.execPath(), {
+      args: [
+        "test",
+        "--no-lock",
+        "--allow-read",
+        "--allow-write",
+        tempDir,
+        "--",
+        "--update",
+        "--no-format",
+      ],
+    });
+    await command.output();
+
+    assertEquals(
+      await Deno.readTextFile(testFile),
+      `import { createAssertInlineSnapshot } from "${SNAPSHOT_MODULE_URL}";
+
+const assertInlineSnapshot = createAssertInlineSnapshot({});
+
+Deno.test("format", () => {
+  assertInlineSnapshot( "hello world", \`"hello world"\` );
+});`,
+    );
+  } finally {
+    await Deno.remove(tempDir, { recursive: true });
+  }
+});