The default "source" module determined by Logger/LogHandler is usually wrong

[gwynne]

Expected behavior

Given this package layout:

.
|- Package.swift
 |- Sources
  |- ModuleA
   |- Subdir1
    |- Impl.swift
  |- ModuleB
   |- Subdir1
    |- Impl.swift

If I perform someLogger.info("hello") in ModuleA/Subdir1/Impl.swift and someLogger.info("world") in ModuleB/Subdir1/Impl.swift, I expect that the source parameters which reach the underlying LogHandler will be, respectively, ModuleA and ModuleB.

Actual behavior

In practice, the source parameter will be Subdir1 in both calls.

SwiftLog version/commit hash

SwiftLog 1.3.0

Swift & OS version (output of swift --version && uname -a)

Apple Swift version 5.3 (swiftlang-1200.0.16.9 clang-1200.0.22.5)
Target: x86_64-apple-darwin19.5.0
Darwin macbookpro.local 19.5.0 Darwin Kernel Version 19.5.0: Tue May 26 20:41:44 PDT 2020; root:xnu-6153.121.2~2/RELEASE_X86_64 x86_64

Further information

This is the natural result of using what is essentially basename(dirname(#file)) as the default for source in Logger.currentModule(filePath:) (

swift-log/Sources/Logging/Logging.swift

Line 762 in 57c6bd0

internal static func currentModule(filePath: String = #file) -> String {

) and Logger.log(level:_:metadata:source:file:function:line:) (

swift-log/Sources/Logging/Logging.swift

Line 75 in 57c6bd0

source: source() ?? Logger.currentModule(filePath: (file)),

). It assumes that all or most packages will use a flat structure for their source files beneath the "per-module" level. This is not the case for the vast majority of packages in, e.g., Vapor (see any of several repositories listed under https://github.com/vapor/ ), and in other common usage in large projects. Because this default is declared on Logger's log() method, it is difficult to override it via, for example, a project's choice of LogHandler, with the result that this new source parameter (otherwise a very useful input) must be ignored in favor of continuing to use such problematic solutions as parsing #file or #filePath (the irony that this behavior is also the cause of this very issue is not lost on me!).

[ktoso]

Damn, feeling silly this slipped through when we were talking about source for weeks 😥 And in my projects I have tons of sub-directories like that as well.

Will ponder some more soon and try to see if a "real" solution is anywhere near in sight...

[ktoso]

Marked as 1.3.1 but I don't think we'll actually solve it there, just a reminder for myself to poke around some more.

[porglezomp]

Is this easy to fix now that we have #fileID which should always start with Module/?

[ktoso]

Do you want to send in a PR @porglezomp ? That'd help a lot :-)

[porglezomp]

It looks like this is actually already fixed in Swift 5.3+, with PR #187.
The behavior is tested in LoggingTest.testLogsEmittedFromSubdirectoryGetCorrectModuleInNewerSwifts, so I think it's safe to close this issue?

[ktoso]

Excellent, thanks for the info and sorry I missed the reply here way back then :)