chmod accepts invalid mode string

[tavianator]

$ touch foo
$ ls -lh foo
-rw-r----- 1 tavianator tavianator 0 Mar 24 21:08 foo
$ ./target/debug/deps/chmod u=rwxg=rx ./foo
$ ls -lh foo
-r-xr----- 1 tavianator tavianator 0 Mar 24 21:08 foo
$ chmod u=rwxg=rx ./foo
chmod: invalid mode: ‘u=rwxg=rx’
Try 'chmod --help' for more information.

Noticed this when writing uutils/findutils#154. chmod shouldn't accept u=rwxg=rx, there needs to be a comma: u=rwx,g=rx. I'm not sure how chmod is interpreting it, but it doesn't act like the comma version.

POSIX gives a grammar for symbolic modes in the chmod docs: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/chmod.html

[Ideflop]

It seems that this issue has been resolved, as running the command ./target/debug/coreutils chmod u=rwxg=rx ./foo currently results in an error message: chmod: invalid operator (expected +, -, or =, but found g). Additionally, the file permissions for foo do not change as shown in the issue example.

Perhaps the error message could be updated to include the comma operator by changing it to chmod: invalid operator (expected +, -, =, or , but found g) ?

[fritzrehde]

This is where the error is thrown:

coreutils/src/uucore/src/lib/features/mode.rs

Lines 90 to 102 in 862a2df

	fn parse_op(mode: &str) -> Result<(char, usize), String> {
	let ch = mode
	.chars()
	.next()
	.ok_or_else(|| "unexpected end of mode".to_owned())?;
	match ch {
	'+' | '-' | '=' => Ok((ch, 1)),
	_ => Err(format!(
	"invalid operator (expected +, -, or =, but found {ch})"
	)),
	}
	}

If I understand correctly, that mode module only handles the parsing of a singular mode, at least I can't see any splitting on , characters. So maybe it would be confusing to add an error message involving , somewhere where none of the parsing involves , characters. But I don't really know of a better place either.

[tertsdiepraam]

The , is parsed here:

coreutils/src/uu/chmod/src/chmod.rs

Line 337 in 862a2df

for mode in cmode_unwrapped.split(',') {

I think it might be nice to unify those. There could be a parse function which returns a Vec of modes, which then also gives a better error.