Best way to get modulemap module names programmatically?

Development Compiler
1

occasionally, a SwiftPM package will give a system library a different name than is declared in the Package.swift manifest:

for example, ZipFoundation has a target named CZLib, but the module is actually named CZlib (lowercase l)

module.modulemap

module CZlib {
    header "shim.h"
    link "z"
    export *
}

what is the best way to detect this name programmatically?

2

If all you care about is the module name, and if the module map is guaranteed to be simple, then your best bet is probably just to do a naïve textual scan of the file.

There are a ton of fun edge (or not-so-edge) cases you might run into though. A modulemap file can contain multiple top-level modules (so a single SwiftPM target could correspond to more than one possible import), submodules are a thing, and you can even have a modulemap that refers to other modulemaps using extern module. So the only truly accurate way to get information out of a modulemap is to build a tool on top of Clang libraries or to reimplement all of that logic, both of which are a bit of a burden.

I wish there was a simple Clang flag you could use to dump the information about a module in a structured parsable format.

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3

thanks Tony, it looks like there’s no good way to detect this at the moment. luckily this is not a critical use case as it only affects system library dependencies in SwiftPM projects.

agree it would be great if the toolchain had a way to dump this information to JSON or something.

4

One way to detect this is that SwiftPM creates a .pcm file for every module in the used module maps in the build directory .build/debug/ModuleCache/, so you could look for what files are in there and dump each pcm file with swiftc -dump-pcm, then check the fields Module map file: and Module name: from that output for all the module names from the module map you want to know about.

I and others have been asking for years for a way to dump the list of C/C++ symbols imported by a module map too, but so far there isn't a way to do that.

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