std@0.139.0/testing/snapshot.ts

Deno standard library
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snapshot.ts
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.import { fromFileUrl, parse, resolve, toFileUrl } from "../path/mod.ts";import { ensureFile, ensureFileSync } from "../fs/mod.ts";import { bold, green, red } from "../fmt/colors.ts";import { assert, AssertionError, equal } from "./asserts.ts";import { buildMessage, diff, diffstr } from "./_diff.ts";
const CAN_NOT_DISPLAY = "[Cannot display]";const SNAPSHOT_DIR = "__snapshots__";const SNAPSHOT_EXT = "snap";
export type SnapshotMode = "assert" | "update";
export type SnapshotOptions<T = unknown> = { /** * Snapshot output directory. Snapshot files will be written to this directory. * This can be relative to the test directory or an absolute path. * * If both `dir` and `path` are specified, the `dir` option will be ignored and * the `path` option will be handled as normal. */ dir?: string; /** * Snapshot mode. Defaults to `assert`, unless the `-u` or `--update` flag is * passed, in which case this will be set to `update`. This option takes higher * priority than the update flag. If the `--update` flag is passed, it will be * ignored if the `mode` option is set. */ mode?: SnapshotMode; /** * Failure message to log when the assertion fails. Specifying this option will * cause the diff not to be logged. */ msg?: string; /** * Name of the snapshot to use in the snapshot file. */ name?: string; /** * Snapshot output path. The shapshot will be written to this file. This can be * a path relative to the test directory or an absolute path. * * If both `dir` and `path` are specified, the `dir` option will be ignored and * the `path` option will be handled as normal. */ path?: string; /** * Function to use when serializing the snapshot. */ serializer?: (actual: T) => string;};
function getErrorMessage(message: string, options: SnapshotOptions) { return typeof options.msg === "string" ? options.msg : message;}
/** * Default serializer for `assertSnapshot`. */export function serialize(actual: unknown): string;export function serialize<T>(actual: T): string;export function serialize(actual: unknown): string { return Deno.inspect(actual, { depth: Infinity, sorted: true, trailingComma: true, compact: false, iterableLimit: Infinity, strAbbreviateSize: Infinity, }).replace(/\\n/g, "\n");}
/** * Converts a string to a valid JavaScript string which can be wrapped in backticks. * * @example * * "special characters (\ ` $) will be escaped" -> "special characters (\\ \` \$) will be escaped" */function escapeStringForJs(str: string) { return str .replace(/\\/g, "\\\\") .replace(/`/g, "\\`") .replace(/\$/g, "\\$");}
let _mode: SnapshotMode;/** * Get the snapshot mode. */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`. */function getIsUpdate(options: SnapshotOptions) { return getMode(options) === "update";}
class AssertSnapshotContext { static contexts = new Map<string, AssertSnapshotContext>();
/** * Returns an instance of `AssertSnapshotContext`. This will be retrieved from * a cache if an instance was already created for a given snapshot file path. */ static fromOptions( testContext: Deno.TestContext, options: SnapshotOptions, ): AssertSnapshotContext { let path: string; const testFilePath = fromFileUrl(testContext.origin); const { dir, base } = parse(testFilePath); if (options.path) { path = resolve(dir, options.path); } else if (options.dir) { path = resolve(dir, options.dir, `${base}.${SNAPSHOT_EXT}`); } else { path = resolve(dir, SNAPSHOT_DIR, `${base}.${SNAPSHOT_EXT}`); }
let context = this.contexts.get(path); if (context) { return context; }
context = new this(toFileUrl(path)); this.contexts.set(path, context); return context; }
private teardownRegistered = false; private currentSnapshots: Map<string, string | undefined> | undefined; private updatedSnapshots = new Map<string, string>(); private snapshotCounts = new Map<string, number>(); private snapshotsUpdated = new Array<string>(); private snapshotFileUrl: URL; private snapshotUpdateQueue = new Array<string>();
constructor(snapshotFileUrl: URL) { this.snapshotFileUrl = snapshotFileUrl; }
/** * Asserts that `this.#currentSnapshots` has been initialized and then returns it. * * Should only be called when `this.#currentSnapshots` has already been initialized. */ private getCurrentSnapshotsInitialized() { assert( this.currentSnapshots, "Snapshot was not initialized. This is a bug in `assertSnapshot`.", ); return this.currentSnapshots; }
/** * Write updates to the snapshot file and log statistics. */ private teardown = () => { const buf = ["export const snapshot = {};"]; const currentSnapshots = this.getCurrentSnapshotsInitialized(); this.snapshotUpdateQueue.forEach((name) => { const updatedSnapshot = this.updatedSnapshots.get(name); const currentSnapshot = currentSnapshots.get(name); let formattedSnapshot: string; if (typeof updatedSnapshot === "string") { formattedSnapshot = updatedSnapshot; } else if (typeof currentSnapshot === "string") { formattedSnapshot = currentSnapshot; } else { // This occurs when `assertSnapshot` is called in "assert" mode but // the snapshot doesn't exist and `assertSnapshot` is also called in // "update" mode. In this case, we have nothing to write to the // snapshot file so we can just exit early return; } formattedSnapshot = escapeStringForJs(formattedSnapshot); formattedSnapshot = formattedSnapshot.includes("\n") ? `\n${formattedSnapshot}\n` : formattedSnapshot; const formattedName = escapeStringForJs(name); buf.push(`\nsnapshot[\`${formattedName}\`] = \`${formattedSnapshot}\`;`); }); const snapshotFilePath = fromFileUrl(this.snapshotFileUrl); ensureFileSync(snapshotFilePath); Deno.writeTextFileSync(snapshotFilePath, buf.join("\n") + "\n");
const contexts = Array.from(AssertSnapshotContext.contexts.values()); if (contexts[contexts.length - 1] === this) { let updated = 0; for (const context of contexts) { updated += context.getUpdatedCount(); } if (updated > 0) { console.log( green(bold(`\n > ${updated} snapshots updated.`)), ); } } };
/** * Returns `this.#currentSnapshots` and if necessary, tries to initialize it by reading existing * snapshots from the snapshot file. If the snapshot mode is `update` and the snapshot file does * not exist then it will be created. */ private async readSnapshotFile(options: SnapshotOptions) { if (this.currentSnapshots) { return this.currentSnapshots; }
if (getIsUpdate(options)) { await ensureFile(fromFileUrl(this.snapshotFileUrl)); }
try { const snapshotFileUrl = this.snapshotFileUrl.toString(); const { snapshot } = await import(snapshotFileUrl); this.currentSnapshots = typeof snapshot === "undefined" ? new Map() : new Map( Object.entries(snapshot).map(([name, snapshot]) => { if (typeof snapshot !== "string") { throw new AssertionError( getErrorMessage( `Corrupt snapshot:\n\t(${name})\n\t${snapshotFileUrl}`, options, ), ); } return [ name, snapshot.includes("\n") ? snapshot.slice(1, -1) : snapshot, ]; }), ); return this.currentSnapshots; } catch (error) { if ( error instanceof TypeError && error.message.startsWith("Module not found") ) { throw new AssertionError( getErrorMessage( "Missing snapshot file.", options, ), ); } throw error; } }
/** * Register a teardown function which writes the snapshot file to disk and logs the number * of snapshots updated after all tests have run. * * This method can safely be called more than once and will only register the teardown * function once. */ public registerTeardown() { if (!this.teardownRegistered) { globalThis.addEventListener("unload", this.teardown); this.teardownRegistered = true; } }
/** * Gets the number of snapshots which have been created with the same name and increments * the count by 1. */ public getCount(snapshotName: string) { let count = this.snapshotCounts.get(snapshotName) || 0; this.snapshotCounts.set(snapshotName, ++count); return count; }
/** * Get an existing snapshot by name or returns `undefined` if the snapshot does not exist. */ public async getSnapshot(snapshotName: string, options: SnapshotOptions) { const snapshots = await this.readSnapshotFile(options); return snapshots.get(snapshotName); }
/** * Update a snapshot by name. Updates will be written to the snapshot file when all tests * have run. If the snapshot does not exist, it will be created. * * Should only be called when mode is `update`. */ public updateSnapshot(snapshotName: string, snapshot: string) { if (!this.snapshotsUpdated.includes(snapshotName)) { this.snapshotsUpdated.push(snapshotName); } const currentSnapshots = this.getCurrentSnapshotsInitialized(); if (!currentSnapshots.has(snapshotName)) { currentSnapshots.set(snapshotName, undefined); } this.updatedSnapshots.set(snapshotName, snapshot); }
/** * Get the number of updated snapshots. */ public getUpdatedCount() { return this.snapshotsUpdated.length; }
/** * Add a snapshot to the update queue. * * Tracks the order in which snapshots were created so that they can be written to * the snapshot file in the correct order. * * Should be called with each snapshot, regardless of the mode, as a future call to * `assertSnapshot` could cause updates to be written to the snapshot file if the * `update` mode is passed in the options. */ public pushSnapshotToUpdateQueue(snapshotName: string) { this.snapshotUpdateQueue.push(snapshotName); }}
/** * Make an assertion that `actual` matches a snapshot. If the snapshot and `actual` do * not a match, then throw. * * Type parameter can be specified to ensure values under comparison have the same type. * For example: * ```ts * import { assertSnapshot } from "./snapshot.ts"; * * Deno.test("snapshot", async (test) => { * await assertSnapshot<number>(test, 2); * }); * ``` */export async function assertSnapshot<T>( t: Deno.TestContext, actual: T, options: SnapshotOptions<T>,): Promise<void>;export async function assertSnapshot<T>( context: Deno.TestContext, actual: T, message?: string,): Promise<void>;export async function assertSnapshot( context: Deno.TestContext, actual: unknown, msgOrOpts?: string | SnapshotOptions<unknown>,): Promise<void> { const options = getOptions(); const assertSnapshotContext = AssertSnapshotContext.fromOptions( context, options, ); const testName = getTestName(context, options); const count = assertSnapshotContext.getCount(testName); const name = `${testName} ${count}`; const snapshot = await assertSnapshotContext.getSnapshot( name, options, );
assertSnapshotContext.pushSnapshotToUpdateQueue(name); const _serialize = options.serializer || serialize; const _actual = _serialize(actual); if (getIsUpdate(options)) { assertSnapshotContext.registerTeardown(); if (!equal(_actual, snapshot)) { assertSnapshotContext.updateSnapshot(name, _actual); } } else { if (!snapshot) { throw new AssertionError( getErrorMessage(`Missing snapshot: ${name}`, options), ); } if (equal(_actual, snapshot)) { return; } let message = ""; try { const stringDiff = !_actual.includes("\n"); const diffResult = stringDiff ? diffstr(_actual, snapshot) : diff(_actual.split("\n"), snapshot.split("\n")); const diffMsg = buildMessage(diffResult, { stringDiff }).join("\n"); message = `Snapshot does not match:\n${diffMsg}`; } catch { message = `Snapshot does not match:\n${red(CAN_NOT_DISPLAY)} \n\n`; } throw new AssertionError( getErrorMessage(message, options), ); }
function getOptions(): SnapshotOptions { if (typeof msgOrOpts === "object" && msgOrOpts !== null) { return msgOrOpts; }
return { msg: msgOrOpts, }; } function getTestName( context: Deno.TestContext, options?: SnapshotOptions, ): string { if (options && options.name) { return options.name; } else if (context.parent) { return `${getTestName(context.parent)} > ${context.name}`; } return context.name; }}