feat(testing/unstable): add assertInlineSnapshot()

_tools/lint_plugin.ts

@@ -322,6 +322,7 @@ export default {
         if (url.href.includes("/testing/mock.ts")) return {};
         if (url.href.includes("/testing/unstable_stub.ts")) return {};
         if (url.href.includes("/testing/snapshot.ts")) return {};
+        if (url.href.includes("/testing/unstable_snapshot.ts")) return {};
 
         // exports from private utils don't need to follow this rule
         if (url.href.includes("/_")) return {};

testing/_snapshot_utils.ts

@@ -0,0 +1,104 @@
+// Copyright 2018-2025 the Deno authors. MIT license.
+import type { SnapshotMode, SnapshotOptions } from "./snapshot.ts";
+import { diff } from "@std/internal/diff";
+import { diffStr } from "@std/internal/diff-str";
+import { buildMessage } from "@std/internal/build-message";
+
+export function getErrorMessage(message: string, options: SnapshotOptions) {
+  return typeof options.msg === "string" ? options.msg : message;
+}
+
+/**
+ * Default serializer for `assertSnapshot`.
+ *
+ * @example Usage
+ * ```ts
+ * import { serialize } from "@std/testing/snapshot";
+ * import { assertEquals } from "@std/assert";
+ *
+ * assertEquals(serialize({ foo: 42 }), "{\n  foo: 42,\n}")
+ * ```
+ *
+ * @param actual The value to serialize
+ * @returns The serialized string
+ */
+export function serialize(actual: unknown): string {
+  return Deno.inspect(actual, {
+    depth: Infinity,
+    sorted: true,
+    trailingComma: true,
+    compact: false,
+    iterableLimit: Infinity,
+    strAbbreviateSize: Infinity,
+    breakLength: Infinity,
+    escapeSequences: false,
+  }).replaceAll("\r", "\\r");
+}
+
+/**
+ * Converts a string to a valid JavaScript string which can be wrapped in backticks.
+ *
+ * @example
+ *
+ * "special characters (\ ` $) will be escaped" -> "special characters (\\ \` \$) will be escaped"
+ */
+export function escapeStringForJs(str: string) {
+  return str
+    .replace(/\\/g, "\\\\")
+    .replace(/`/g, "\\`")
+    .replace(/\$/g, "\\$");
+}
+
+let _mode: SnapshotMode;
+/**
+ * Get the snapshot mode.
+ */
+export function getMode(options: SnapshotOptions) {
+  if (options.mode) {
+    return options.mode;
+  } else if (_mode) {
+    return _mode;
+  } else {
+    _mode = Deno.args.some((arg) => arg === "--update" || arg === "-u")
+      ? "update"
+      : "assert";
+    return _mode;
+  }
+}
+
+/**
+ * Return `true` when snapshot mode is `update`.
+ */
+export function getIsUpdate(options: SnapshotOptions) {
+  return getMode(options) === "update";
+}
+
+export function getOptions<T>(
+  msgOrOpts?: string | T,
+): T {
+  if (msgOrOpts === undefined) return {} as T;
+
+  if (typeof msgOrOpts === "object" && msgOrOpts !== null) {
+    return msgOrOpts;
+  }
+
+  return { msg: msgOrOpts } as T;
+}
+
+export function getSnapshotNotMatchMessage(
+  actualSnapshot: string,
+  expectedSnapshot: string,
+  options: SnapshotOptions,
+) {
+  const stringDiff = !actualSnapshot.includes("\n");
+  const diffResult = stringDiff
+    ? diffStr(actualSnapshot, expectedSnapshot)
+    : diff(actualSnapshot.split("\n"), expectedSnapshot.split("\n"));
+  const diffMsg = buildMessage(diffResult, { stringDiff }).join("\n");
+  const message =
+    `Snapshot does not match:\n${diffMsg}\nTo update snapshots, run\n    deno test --allow-read --allow-write [files]... -- --update\n`;
+  return getErrorMessage(message, options);
+}
+
+// TODO (WWRS): Remove this when we drop support for Deno 1.x
+export const LINT_SUPPORTED = !Deno.version.deno.startsWith("1.");

testing/deno.json

@@ -8,6 +8,7 @@
     "./time": "./time.ts",
     "./types": "./types.ts",
     "./unstable-bdd": "./unstable_bdd.ts",
+    "./unstable-snapshot": "./unstable_snapshot.ts",
     "./unstable-stub": "./unstable_stub.ts",
     "./unstable-types": "./unstable_types.ts"
   }