fix(expect): support expect.addSnapshotSerializer

expect/_serializer.ts

@@ -0,0 +1,15 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+import type { SnapshotPlugin } from "./_types.ts";
+
+const INTERNAL_PLUGINS: SnapshotPlugin[] = [
+  // TODO(eryue0220): support internal snapshot serializer plugins
+];
+
+export function addSerializer(plugin: SnapshotPlugin) {
+  INTERNAL_PLUGINS.unshift(plugin);
+}
+
+export function getSerializer() {
+  return INTERNAL_PLUGINS;
+}

expect/_serializer_test.ts

@@ -0,0 +1,23 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+import { expect } from "./expect.ts";
+import { addSerializer, getSerializer } from "./_serializer.ts";
+import type { SnapshotPlugin } from "./_types.ts";
+
+const foo: SnapshotPlugin = {
+  serialize() {
+    return "foot";
+  },
+  test() {
+    return false;
+  },
+};
+
+Deno.test("initial serializer", () => {
+  expect(getSerializer()).toHaveLength(0);
+});
+
+Deno.test("add serializer", () => {
+  addSerializer(foo);
+  expect(getSerializer()).toHaveLength(1);
+});

expect/_types.ts

@@ -915,3 +915,5 @@ export interface OldSnapshotPlugin {
   ) => string;
   test: Test;
 }
+
+export type SnapshotPlugin = NewSnapshotPlugin | OldSnapshotPlugin;

expect/expect.ts

@@ -59,9 +59,10 @@ import {
   toStrictEqual,
   toThrow,
 } from "./_matchers.ts";
+import { addSerializer } from "./_serializer.ts";
 import { isPromiseLike } from "./_utils.ts";
 import * as asymmetricMatchers from "./_asymmetric_matchers.ts";
-import type { Tester } from "./_types.ts";
+import type { SnapshotPlugin, Tester } from "./_types.ts";
 
 export type { AnyConstructor, Async, Expected } from "./_types.ts";
 
@@ -599,3 +600,21 @@ expect.not = {
   stringContaining: asymmetricMatchers.stringNotContaining,
   stringMatching: asymmetricMatchers.stringNotMatching,
 };
+/**
+ * `expect.addSnapshotSerializer` adds a module that formats application-specific data structures.
+ *
+ * For an individual test file, an added module precedes any modules from snapshotSerializers configuration,
+ * which precede the default snapshot serializers for built-in JavaScript types.
+ * The last module added is the first module tested.
+ *
+ * @example
+ * ```ts no-eval
+ * import { expect } from "@std/expect";
+ * import serializerAnsi from "npm:jest-snapshot-serializer-ansi";
+ *
+ * expect.addSnapshotSerializer(serializerAnsi);
+ * ```
+ */
+expect.addSnapshotSerializer = addSerializer as (
+  plugin: SnapshotPlugin,
+) => void;

expect/mod.ts

@@ -63,6 +63,7 @@
  *   - {@linkcode expect.stringMatching}
  *   - {@linkcode expect.not.stringMatching}
  * - Utilities:
+ *   - {@linkcode expect.addSnapshotSerializer}
  *   - {@linkcode expect.assertions}
  *   - {@linkcode expect.addEqualityTester}
  *   - {@linkcode expect.extend}
@@ -74,8 +75,6 @@
  *   - `toMatchInlineSnapshot`
  *   - `toThrowErrorMatchingSnapshot`
  *   - `toThrowErrorMatchingInlineSnapshot`
- * - Utilities:
- *   - `expect.addSnapshotSerializer`
  *
  * The tracking issue to add support for unsupported parts of the API is
  * {@link https://github.com/denoland/std/issues/3964}.