tracing-config.lua

function RegisterExtractorPack(id)
    local extractorDirectory = GetPlatformToolsDirectory()
    local relativeSwiftExtractor = extractorDirectory .. 'extractor'
    local swiftExtractor = AbsolutifyExtractorPath(id, relativeSwiftExtractor)
    local resourceDirectory = AbsolutifyExtractorPath(id, 'resource-dir' .. PathSep .. PlatformDirectory)

    function indexOf(array, value)
        for i, v in ipairs(array) do
            if v == value then
                return i
            end
        end
        return nil
    end

    function startswith(text, prefix)
        return string.find(text, prefix, 1, true) == 1
    end

    -- removes unsupported CLI arg including the following how_many args
    function strip_unsupported_arg(args, arg, how_many)
        local index = indexOf(args, arg)
        if index then
            table.remove(args, index)
            while (how_many > 0)
            do
                table.remove(args, index)
                how_many = how_many - 1
            end
        end
    end

    -- removes unsupported -Xcc flag, e.g, calling strip_unsupported_xcc_arg('-foo', 2) against
    -- swift -Xcc -foo -Xcc -bar main.swift
    -- will only leave 'swift main.swift' removing both -Xcc -foo, and also -Xcc -bar
    -- removes unsupported CLI arg passed to clang via -Xcc together with the following how_many args
    function strip_unsupported_clang_arg(args, arg, how_many)
        local index = indexOf(args, arg)
        if index and index > 0 and args[index - 1] == '-Xcc' then
            index = index - 1  -- start from -Xcc
            how_many = 2 * (how_many + 1)  -- need to remove initial -Xcc <arg> as well as following -Xcc prefixed flags
            while (how_many > 0)
            do
                table.remove(args, index)
                how_many = how_many - 1
            end
        end
    end

    function strip_unsupported_args(args)
        strip_unsupported_arg(args, '-emit-localized-strings', 0)
        strip_unsupported_arg(args, '-emit-localized-strings-path', 1)
        strip_unsupported_arg(args, '-stack-check', 0)
        strip_unsupported_arg(args, '-experimental-skip-non-inlinable-function-bodies-without-types', 0)
        strip_unsupported_clang_arg(args, '-ivfsstatcache', 1)
    end

    -- xcodebuild does not always specify the -resource-dir in which case the compiler falls back
    -- to a resource-dir based on its path. We want to know what is the original resource-dir in
    -- all cases so that we can patch it with out own
    function find_original_resource_dir(compilerPath, args)
      local resource_dir_index = indexOf(args, '-resource-dir')
      if resource_dir_index and args[resource_dir_index + 1] then
        return args[resource_dir_index + 1]
      end
      -- derive -resource-dir based on the compilerPath
      -- e.g.: /usr/bin/swift-frontend -> /usr/bin/../lib/swift
      local second_last_slash_index = string.find(compilerPath, "/[^/]*/[^/]*$")
      local usr_dir = string.sub(compilerPath, 1, second_last_slash_index)
      return usr_dir .. '/lib/swift'
    end

    -- replace or add our own resource directory
    function replace_resource_dir(compilerPath, args)
        local originalResourceDir = find_original_resource_dir(compilerPath, args)
        for index, value in ipairs(args) do
            if startswith(value, originalResourceDir) then
                args[index] = resourceDirectory .. string.sub(value, #originalResourceDir + 1, -1)
            end
        end
        if not indexOf(args, '-resource-dir') then
            table.insert(args, '-resource-dir')
            table.insert(args, resourceDirectory)
        end
    end

    function SwiftMatcher(compilerName, compilerPath, compilerArguments, lang)
        -- Only match binaries names `swift-frontend`
        if compilerName ~= 'swift-frontend' then
            return nil
        end
        -- Skip the invocation in case it's not called in `-frontend` mode
        if compilerArguments.argv[1] ~= '-frontend' then
            return nil
        end

        -- Drop the `-frontend` argument
        table.remove(compilerArguments.argv, 1)

        -- Skip "info" queries in case there is nothing to extract
        if compilerArguments.argv[1] == '-print-target-info' then
            return nil
        end
        if compilerArguments.argv[1] == '-emit-supported-features' then
            return nil
        end

        strip_unsupported_args(compilerArguments.argv)
        replace_resource_dir(compilerPath, compilerArguments.argv)

        return {
            trace = true,
            replace = false,
            order = ORDER_AFTER,
            invocation = { path = swiftExtractor, arguments = compilerArguments }
        }
    end
    return {
        SwiftMatcher,
        CreatePatternMatcher({ '^lsregister$' }, MatchCompilerName, nil,
                { trace = false }),
        CreatePatternMatcher({ '^codesign$' }, MatchCompilerName, nil,
                { trace = false }),
        CreatePatternMatcher({ '^sandbox%-exec$' }, MatchCompilerName, nil,
                { trace = false }),
    }
end

-- Return a list of minimum supported versions of the configuration file format
-- return one entry per supported major version.
function GetCompatibleVersions()
    return { '1.0.0' }
end