// Copyright 2018-2025 the Deno authors. MIT license.
// This module is browser compatible.
import { buildMessage } from "@std/internal/build-message";
import { diff } from "@std/internal/diff";
import { diffStr } from "@std/internal/diff-str";
import { format } from "@std/internal/format";
import { red } from "@std/internal/styles";
import { AssertionError } from "./assertion_error.ts";
/**
* Make an assertion that `actual` and `expected` are strictly equal, using
* {@linkcode Object.is} for equality comparison. If not, then throw.
*
* @example Usage
* ```ts ignore
* import { assertStrictEquals } from "@std/assert";
*
* const a = {};
* const b = a;
* assertStrictEquals(a, b); // Doesn't throw
*
* const c = {};
* const d = {};
* assertStrictEquals(c, d); // Throws
* ```
*
* @typeParam T The type of the expected value.
* @param actual The actual value to compare.
* @param expected The expected value to compare.
* @param msg The optional message to display if the assertion fails.
*/
export function assertStrictEquals<T>(
actual: unknown,
expected: T,
msg?: string,
): asserts actual is T {
if (Object.is(actual, expected)) {
return;
}
const msgSuffix = msg ? `: ${msg}` : ".";
let message: string;
const actualString = format(actual);
const expectedString = format(expected);
if (actualString === expectedString) {
const withOffset = actualString
.split("\n")
.map((l) => ` ${l}`)
.join("\n");
message =
`Values have the same structure but are not reference-equal${msgSuffix}\n\n${
red(withOffset)
}\n`;
} else {
const stringDiff = (typeof actual === "string") &&
(typeof expected === "string");
const diffResult = stringDiff
? diffStr(actual as string, expected as string)
: diff(actualString.split("\n"), expectedString.split("\n"));
const diffMsg = buildMessage(diffResult, { stringDiff }).join("\n");
message = `Values are not strictly equal${msgSuffix}\n${diffMsg}`;
}
throw new AssertionError(message);
}
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