Error handling for FileAccess.get_file_as_*

[paulloz]

What happens on errors in FileAccess.get_file_as_bytes and FileAccess.get_file_as_string is currently undocumented. It's also impossible to retrieve the actual error that happened.

---

• Assign last error in said FileAccess.get_file_as_bytes and FileAccess.get_file_as_string
• Document error handling for said methods

[RandomShaper]

As far as I can see, last_file_open_error should only be set in the case of an failed open. In that line of thought, get_file_as_bytes could just set it if the opening fails:

	Error open_error = OK;
	Ref<FileAccess> f = FileAccess::open(p_path, READ, open_error);
	if (f.is_null()) {
		last_file_open_error = open_error;
		if (r_error) { // if error requested, do not throw error
			*r_error = open_error;
			return Vector<uint8_t>();
		}
		ERR_FAIL_V_MSG(Vector<uint8_t>(), "Can't open file from path '" + String(p_path) + "'.");
	}

What do you think?

[paulloz]

@RandomShaper That was my initial line of thought too (with the last_file_open_error assignation above the if, to always assign it). In the end, I wasn't sure what was best, but I'm fine with any.

[akien-mga]

Looks good to me.

[akien-mga]

As far as I can see, last_file_open_error should only be set in the case of an failed open.

I had missed this when reviewing, but I don't think that's correct with the current implementation.

Ref<FileAccess> FileAccess::_open(const String &p_path, ModeFlags p_mode_flags) {
	Error err = OK;
	Ref<FileAccess> fa = open(p_path, p_mode_flags, &err);
	last_file_open_error = err;
	if (err) {
		return Ref<FileAccess>();
	}
	return fa;
}

Ref<FileAccess> FileAccess::open_encrypted(const String &p_path, ModeFlags p_mode_flags, const Vector<uint8_t> &p_key) {
	Ref<FileAccess> fa = _open(p_path, p_mode_flags);
	if (fa.is_null()) {
		return fa;
	}

	Ref<FileAccessEncrypted> fae;
	fae.instantiate();
	Error err = fae->open_and_parse(fa, p_key, (p_mode_flags == WRITE) ? FileAccessEncrypted::MODE_WRITE_AES256 : FileAccessEncrypted::MODE_READ);
	last_file_open_error = err;
	if (err) {
		return Ref<FileAccess>();
	}
	return fae;
}

last_file_open_error is always set, whether it succeeds or fails.

The name might be a bit confusing, but it's the last Error value (which includes OK), not the last time there was an "error" (failure).

It might be worth clarifying this in the documentation for FileAccess and DirAccess get_open_error.

[akien-mga]

The CI error is a GitHub Actions fluke. Rebasing on top of the just merged #83147 might help (though not 100% sure yet).

[akien-mga]

Thanks!