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asserts.ts
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asserts.ts
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
/** This module is browser compatible. Do not rely on good formatting of values
* for AssertionError messages in browsers. */
import { red, green, white, gray, bold, stripColor } from "../fmt/colors.ts";
import diff, { DiffType, DiffResult } from "./diff.ts";
const CAN_NOT_DISPLAY = "[Cannot display]";
interface Constructor {
// eslint-disable-next-line @typescript-eslint/no-explicit-any
new (...args: any[]): any;
}
export class AssertionError extends Error {
constructor(message: string) {
super(message);
this.name = "AssertionError";
}
}
export function _format(v: unknown): string {
let string = globalThis.Deno
? Deno.inspect(v, {
depth: Infinity,
sorted: true,
trailingComma: true,
compact: false,
iterableLimit: Infinity,
})
: String(v);
if (typeof v == "string") {
string = `"${string.replace(/(?=["\\])/g, "\\")}"`;
}
return string;
}
function createColor(diffType: DiffType): (s: string) => string {
switch (diffType) {
case DiffType.added:
return (s: string): string => green(bold(s));
case DiffType.removed:
return (s: string): string => red(bold(s));
default:
return white;
}
}
function createSign(diffType: DiffType): string {
switch (diffType) {
case DiffType.added:
return "+ ";
case DiffType.removed:
return "- ";
default:
return " ";
}
}
function buildMessage(diffResult: ReadonlyArray<DiffResult<string>>): string[] {
const messages: string[] = [];
messages.push("");
messages.push("");
messages.push(
` ${gray(bold("[Diff]"))} ${red(bold("Actual"))} / ${
green(bold("Expected"))
}`,
);
messages.push("");
messages.push("");
diffResult.forEach((result: DiffResult<string>): void => {
const c = createColor(result.type);
messages.push(c(`${createSign(result.type)}${result.value}`));
});
messages.push("");
return messages;
}
function isKeyedCollection(x: unknown): x is Set<unknown> {
return [Symbol.iterator, "size"].every((k) => k in (x as Set<unknown>));
}
export function equal(c: unknown, d: unknown): boolean {
const seen = new Map();
return (function compare(a: unknown, b: unknown): boolean {
// Have to render RegExp & Date for string comparison
// unless it's mistreated as object
if (
a &&
b &&
((a instanceof RegExp && b instanceof RegExp) ||
(a instanceof URL && b instanceof URL))
) {
return String(a) === String(b);
}
if (a instanceof Date && b instanceof Date) {
return a.getTime() === b.getTime();
}
if (Object.is(a, b)) {
return true;
}
if (a && typeof a === "object" && b && typeof b === "object") {
if (seen.get(a) === b) {
return true;
}
if (Object.keys(a || {}).length !== Object.keys(b || {}).length) {
return false;
}
if (isKeyedCollection(a) && isKeyedCollection(b)) {
if (a.size !== b.size) {
return false;
}
let unmatchedEntries = a.size;
for (const [aKey, aValue] of a.entries()) {
for (const [bKey, bValue] of b.entries()) {
/* Given that Map keys can be references, we need
* to ensure that they are also deeply equal */
if (
(aKey === aValue && bKey === bValue && compare(aKey, bKey)) ||
(compare(aKey, bKey) && compare(aValue, bValue))
) {
unmatchedEntries--;
}
}
}
return unmatchedEntries === 0;
}
const merged = { ...a, ...b };
for (const key in merged) {
type Key = keyof typeof merged;
if (!compare(a && a[key as Key], b && b[key as Key])) {
return false;
}
}
seen.set(a, b);
return true;
}
return false;
})(c, d);
}
/** Make an assertion, error will be thrown if `expr` does not have truthy value. */
export function assert(expr: unknown, msg = ""): asserts expr {
if (!expr) {
throw new AssertionError(msg);
}
}
/**
* Make an assertion that `actual` and `expected` are equal, deeply. If not
* deeply equal, then throw.
*
* Type parameter can be specified to ensure values under comparison have the same type.
* For example:
*```ts
*assertEquals<number>(1, 2)
*```
*/
export function assertEquals(
actual: unknown,
expected: unknown,
msg?: string,
): void;
export function assertEquals<T>(actual: T, expected: T, msg?: string): void;
export function assertEquals(
actual: unknown,
expected: unknown,
msg?: string,
): void {
if (equal(actual, expected)) {
return;
}
let message = "";
const actualString = _format(actual);
const expectedString = _format(expected);
try {
const diffResult = diff(
actualString.split("\n"),
expectedString.split("\n"),
);
const diffMsg = buildMessage(diffResult).join("\n");
message = `Values are not equal:\n${diffMsg}`;
} catch (e) {
message = `\n${red(CAN_NOT_DISPLAY)} + \n\n`;
}
if (msg) {
message = msg;
}
throw new AssertionError(message);
}
/**
* Make an assertion that `actual` and `expected` are not equal, deeply.
* If not then throw.
*
* Type parameter can be specified to ensure values under comparison have the same type.
* For example:
*```ts
*assertNotEquals<number>(1, 2)
*```
*/
export function assertNotEquals(
actual: unknown,
expected: unknown,
msg?: string,
): void;
export function assertNotEquals<T>(actual: T, expected: T, msg?: string): void;
export function assertNotEquals(
actual: unknown,
expected: unknown,
msg?: string,
): void {
if (!equal(actual, expected)) {
return;
}
let actualString: string;
let expectedString: string;
try {
actualString = String(actual);
} catch (e) {
actualString = "[Cannot display]";
}
try {
expectedString = String(expected);
} catch (e) {
expectedString = "[Cannot display]";
}
if (!msg) {
msg = `actual: ${actualString} expected: ${expectedString}`;
}
throw new AssertionError(msg);
}
/**
* Make an assertion that `actual` and `expected` are strictly equal. If
* not then throw.
* ```ts
* assertStrictEquals(1, 2)
* ```
*/
export function assertStrictEquals<T>(
actual: T,
expected: T,
msg?: string,
): void {
if (actual === expected) {
return;
}
let message: string;
if (msg) {
message = msg;
} else {
const actualString = _format(actual);
const expectedString = _format(expected);
if (actualString === expectedString) {
const withOffset = actualString
.split("\n")
.map((l) => ` ${l}`)
.join("\n");
message =
`Values have the same structure but are not reference-equal:\n\n${
red(withOffset)
}\n`;
} else {
try {
const diffResult = diff(
actualString.split("\n"),
expectedString.split("\n"),
);
const diffMsg = buildMessage(diffResult).join("\n");
message = `Values are not strictly equal:\n${diffMsg}`;
} catch (e) {
message = `\n${red(CAN_NOT_DISPLAY)} + \n\n`;
}
}
}
throw new AssertionError(message);
}
/**
* Make an assertion that actual contains expected. If not
* then thrown.
*/
export function assertStringContains(
actual: string,
expected: string,
msg?: string,
): void {
if (!actual.includes(expected)) {
if (!msg) {
msg = `actual: "${actual}" expected to contain: "${expected}"`;
}
throw new AssertionError(msg);
}
}
/**
* Make an assertion that `actual` contains the `expected` values.
* If not then an error will be thrown.
*
* Type parameter can be specified to ensure values under comparison have the same type.
* For example:
*```ts
*assertArrayContains<number>([1, 2], [2])
*```
*/
export function assertArrayContains(
actual: ArrayLike<unknown>,
expected: ArrayLike<unknown>,
msg?: string,
): void;
export function assertArrayContains<T>(
actual: ArrayLike<T>,
expected: ArrayLike<T>,
msg?: string,
): void;
export function assertArrayContains(
actual: ArrayLike<unknown>,
expected: ArrayLike<unknown>,
msg?: string,
): void {
const missing: unknown[] = [];
for (let i = 0; i < expected.length; i++) {
let found = false;
for (let j = 0; j < actual.length; j++) {
if (equal(expected[i], actual[j])) {
found = true;
break;
}
}
if (!found) {
missing.push(expected[i]);
}
}
if (missing.length === 0) {
return;
}
if (!msg) {
msg = `actual: "${_format(actual)}" expected to contain: "${
_format(expected)
}"\nmissing: ${_format(missing)}`;
}
throw new AssertionError(msg);
}
/**
* Make an assertion that `actual` match RegExp `expected`. If not
* then thrown
*/
export function assertMatch(
actual: string,
expected: RegExp,
msg?: string,
): void {
if (!expected.test(actual)) {
if (!msg) {
msg = `actual: "${actual}" expected to match: "${expected}"`;
}
throw new AssertionError(msg);
}
}
/**
* Forcefully throws a failed assertion
*/
export function fail(msg?: string): void {
// eslint-disable-next-line @typescript-eslint/no-use-before-define
assert(false, `Failed assertion${msg ? `: ${msg}` : "."}`);
}
/**
* Executes a function, expecting it to throw. If it does not, then it
* throws. An error class and a string that should be included in the
* error message can also be asserted.
*/
export function assertThrows<T = void>(
fn: () => T,
ErrorClass?: Constructor,
msgIncludes = "",
msg?: string,
): Error {
let doesThrow = false;
let error = null;
try {
fn();
} catch (e) {
if (e instanceof Error === false) {
throw new AssertionError("A non-Error object was thrown.");
}
if (ErrorClass && !(e instanceof ErrorClass)) {
msg =
`Expected error to be instance of "${ErrorClass.name}", but was "${e.constructor.name}"${
msg ? `: ${msg}` : "."
}`;
throw new AssertionError(msg);
}
if (
msgIncludes &&
!stripColor(e.message).includes(stripColor(msgIncludes))
) {
msg =
`Expected error message to include "${msgIncludes}", but got "${e.message}"${
msg ? `: ${msg}` : "."
}`;
throw new AssertionError(msg);
}
doesThrow = true;
error = e;
}
if (!doesThrow) {
msg = `Expected function to throw${msg ? `: ${msg}` : "."}`;
throw new AssertionError(msg);
}
return error;
}
/**
* Executes a function which returns a promise, expecting it to throw or reject.
* If it does not, then it throws. An error class and a string that should be
* included in the error message can also be asserted.
*/
export async function assertThrowsAsync<T = void>(
fn: () => Promise<T>,
ErrorClass?: Constructor,
msgIncludes = "",
msg?: string,
): Promise<Error> {
let doesThrow = false;
let error = null;
try {
await fn();
} catch (e) {
if (e instanceof Error === false) {
throw new AssertionError("A non-Error object was thrown or rejected.");
}
if (ErrorClass && !(e instanceof ErrorClass)) {
msg =
`Expected error to be instance of "${ErrorClass.name}", but got "${e.name}"${
msg ? `: ${msg}` : "."
}`;
throw new AssertionError(msg);
}
if (
msgIncludes &&
!stripColor(e.message).includes(stripColor(msgIncludes))
) {
msg =
`Expected error message to include "${msgIncludes}", but got "${e.message}"${
msg ? `: ${msg}` : "."
}`;
throw new AssertionError(msg);
}
doesThrow = true;
error = e;
}
if (!doesThrow) {
msg = `Expected function to throw${msg ? `: ${msg}` : "."}`;
throw new AssertionError(msg);
}
return error;
}
/** Use this to stub out methods that will throw when invoked. */
export function unimplemented(msg?: string): never {
throw new AssertionError(msg || "unimplemented");
}
/** Use this to assert unreachable code. */
export function unreachable(): never {
throw new AssertionError("unreachable");
}