dirname returns wrong result When the path is the root

[Hanaasagi]

What version of Bun is running?

0.7.0

What platform is your computer?

Linux 6.4.4-arch1-1 x86_64 unknown

What steps can reproduce the bug?

const path = require("path");
const assert = require("assert");
assert.strictEqual(path.posix.dirname("/"), "/");

What is the expected behavior?

No `AssertionError``.

What do you see instead?

AssertionError: Expected values to be strictly equal:

'.' !== '/'

 code: "ERR_ASSERTION"

Additional information

I think this bug is related to #2676

Here, the returned value should be determined by more context details instead of returning a ..

bun/src/bun.js/node/types.zig

Lines 1699 to 1702 in 967ccb5

	const out = if (isWindows)
	std.fs.path.dirnameWindows(base_slice) orelse "."
	else
	std.fs.path.dirnamePosix(base_slice) orelse ".";

[Hanaasagi]

After running the dirname related test files in Nodejs, I found some other incompatibilities.

assert.strictEqual(path.posix.dirname("////"), "/");
assert.strictEqual(path.posix.dirname("//a"), "//");
assert.strictEqual(path.win32.dirname("c:\\"), "c:\\");
assert.strictEqual(path.win32.dirname("\\"), "\\");

assert.strictEqual(path.win32.dirname("c:"), "c:");
assert.strictEqual(path.win32.dirname("c:foo"), "c:");
assert.strictEqual(path.win32.dirname("c:foo\\"), "c:");
assert.strictEqual(path.win32.dirname("\\\\unc\\share"), "\\\\unc\\share");
assert.strictEqual(path.win32.dirname("/"), "/");
assert.strictEqual(path.win32.dirname("////"), "/");

Ref: https://github.com/nodejs/node/blob/main/test/parallel/test-path-dirname.js

[Jarred-Sumner]

I’m surprised we still have these bugs

[Hanaasagi]

I think i can fix this.

[Jarred-Sumner]

Please do