Swift: Make tracer config handle resource-dirs passed to clang

[jketema]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the Swift tracer configuration to properly handle resource directories passed to clang through the -Xcc flag. The changes allow the tracer to extract the correct Swift resource directory even when clang-specific resource directories are specified.

• Enhanced resource directory detection to handle -Xcc prefixed arguments
• Added logic to strip /clang suffix from clang resource directories to derive Swift resource directories
• Fixed a minor string concatenation issue in the fallback resource directory path

[redsun82]

nit: while this works, it's slightly at odds with the comment, that speaks about an -Xcc preceding -resource-dir. So maybe

Suggested change

	if args[resource_dir_index + 1] and args[resource_dir_index + 1] ~= '-Xcc' then
	return args[resource_dir_index + 1]
	elseif args[resource_dir_index + 2] then
	local clang_index = string.find(args[resource_dir_index + 2], "/clang$")
	if clang_index and clang_index - 1 > 0 then
	return string.sub(args[resource_dir_index + 2], 1, clang_index - 1)
	end
	end
	if ~(args[resource_dir_index - 1] and args[resource_dir_index - 1] == '-Xcc') then
	return args[resource_dir_index + 1]
	elseif args[resource_dir_index + 1] and args[resource_dir_index + 1] == '-Xcc' and args[resource_dir_index + 2] then
	local clang_index = string.find(args[resource_dir_index + 2], "/clang$")
	if clang_index and clang_index - 1 > 0 then
	return string.sub(args[resource_dir_index + 2], 1, clang_index - 1)
	end
	end

would be more semantically correct in a pedantic way?

(looking back, it might also be good to somehow shorten the resource_dir_index name, I wouldn't mind just pos or found)

[redsun82]

(notice one doesn't need to do bound checking in Lua, because referencing out-of-bounds indexes in a table will just give nil, including on 0 and negative indexes)

[jketema]

would be more semantically correct in a pedantic way?

In the if-case do we still need to check that args[resource_dir_index + 1] exists? Just to be sure we end up in the backup case if args[resource_dir_index + 1] is missing

(notice one doesn't need to do bound checking in Lua, because referencing out-of-bounds indexes in a table will just give nil, including on 0 and negative indexes)

Is there specific code you're referring to?

[redsun82]

In the if-case do we still need to check that args[resource_dir_index + 1] exists? Just to be sure we end up in the backup case if args[resource_dir_index + 1] is missing

I was thinking about that. Even if we did the fallback on a truncated args vector ending with -resource-dir (which is an ill-formed command line we shouldn't ever encounter), we currently return nil here which is probably a bad thing. So maybe the full pedantic code should be

        local found = indexOf(args, '-resource-dir')
        if found and args[found + 1] then
            if args[found - 1] ~= '-Xcc' then
                return args[found + 1]
            elseif args[found + 1] == '-Xcc' and args[found + 2] then
                local clang_index = string.find(args[found + 2], "/clang$")
                if clang_index and clang_index - 1 > 0 then
                    return string.sub(args[found + 2], 1, clang_index - 1)
                end
            end
        end

this goes for the fallback early if -resource-dir is the last argument, takes its direct successor if the preceding one is not -Xcc (which also covers the case in which it is nil, when found == 1), and takes the clang resource dir only for a well formed -Xcc -resource-dir -Xcc <path>/clang sequence. And it covers the devilish case in which someone very sadistic is pointing -resource-dir to a local -Xcc directory 😆

Is there specific code you're referring to?

I was referring to my suggestion, where doing args[pos - 1] == '-Xcc' doesn't need bound checking

[jketema]

I've implemented your fully pedantic review suggestion 😄

[redsun82]

thanks a lot!