diagnose-api-breaking-changes does not understand submodules

[PeterAdams-A]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

When running diagnose-api-breaking-changes against a package which contains git submodules the tool does not appear to understand that it needs to get the submodules.

The project in question can be found here - https://github.com/apple/swift-async-dns-resolver

Expected behavior

API breakage tool should checkout submodules as required.

Actual behavior

It appears not too...

swift package diagnose-api-breaking-changes main
Building for debugging...
[71/71] Compiling AsyncDNSResolver DNSResolver_c-ares.swift
Build complete! (2.01s)
warning: '92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout': found 1 file(s) which are unhandled; explicitly declare them as resources or exclude from the target
/Users/petera/XCode/swift-async-dns-resolver/.build/arm64-apple-macosx/apidiff/92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout/Sources/AsyncDNSResolver/Docs.docc
Building for debugging...
[73/73] Compiling AsyncDNSResolver AsyncDNSResolver.swift
Build complete! (16.02s)
error: baseline for AsyncDNSResolver contains no symbols, swift-api-digester output: :1:9: note: in file included from :1:
#import "/Users/petera/XCode/swift-async-dns-resolver/.build/arm64-apple-macosx/apidiff/92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout/Sources/CAsyncDNSResolver/include/CAsyncDNSResolver.h"
^
/Users/petera/XCode/swift-async-dns-resolver/.build/arm64-apple-macosx/apidiff/92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout/Sources/CAsyncDNSResolver/include/CAsyncDNSResolver.h:23:10: note: in file included from /Users/petera/XCode/swift-async-dns-resolver/.build/arm64-apple-macosx/apidiff/92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout/Sources/CAsyncDNSResolver/include/CAsyncDNSResolver.h:23:
#include "../c-ares/include/ares.h"
^
/Users/petera/XCode/swift-async-dns-resolver/.build/arm64-apple-macosx/apidiff/92ae16ff641eec3a6bb49bec723870ce5a02594a-checkout/Sources/CAsyncDNSResolver/include/../c-ares/include/ares.h:22:10: error: 'ares_build.h' file not found
#include "ares_build.h" /* c-ares build definitions */
^
:0: error: could not build Objective-C module 'CAsyncDNSResolver'
Failed to load module: AsyncDNSResolver
error: fatalError

Steps to reproduce

1. Check out https://github.com/apple/swift-async-dns-resolver (and submodules)
2. Make a change.
3. Try and see if you've changed the API - swift package diagnose-api-breaking-changes main

Swift Package Manager version/commit hash

6.0

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

Swift 6.0 - darwin and linux both seem to not work.