Open cgrindel opened 2 years ago
Looks like I will need to parse the Package.swift to get any C-specific settings/options.
Example: swift-nio with CSetting Example: Yams with CSetting
Notes on getting libwebp
in interesting_deps
example to build:
includes = [
"include/webp",
"libwebp",
"libwebp/src",
],
Over the past week or so, I have been working on a proof-of-concept to understand what it would take to introduce a build_mode
to spm_repositories
. Setting this attribute to bazel
would change how rules_spm
works underneath the covers. Instead of building the dependent packages using SPM, it would generate Bazel build files allowing the targets to be built using the normal Bazel toolchains. I was able to successfully build and use Swift packages with Swift targets and generic clang targets. Unfortunately, configuring clang targets with custom build settings requires more information than a package description provides.
To be able to properly build clang targets with custom build settings, one needs to retrieve and apply these settings (e.g. defines, public header paths). The current scheme for downloading and reading these manifest files during the repository fetch phase requires code that can parse the manifest and present the information in a means that is readable by Starlark code. Unfortunately, there is no Swift package manifest parser written in Starlark. One can write a parser in Starlark and maintain it as SPM evolves. The question is whether that is the best path forward.
This conundrum is not new to this project. The same decision had to be made when figuring out how to read data from module.modulemap
files. At the time, we opted to write a modulemap parser in Starlark thinking that the format was fairly mature and did not appear to be changing much.
To avoid having to write a custom parser, I wrote a simple Swift binary that reads a Swift package manifest and dumps information about it to JSON. The JSON is then read by Starlark code. The approach works. The problem is how one gets and uses the binary from code that is run during Bazel's fetch phase. As of this writing, the current code uses swift run
to build and execute the parser. This works OK if there is only one spm_repositories
declaration. However, if there are multiple declarations, one will experience an error due to two Swift processes trying to build the same package. I could work around this by ensuring that two processes never build the same code simultaneously. However, that would require duplicating the code and the compilation (ugh) or inventing some kind of semaphore that only allows one build to run (double ugh).
So, I am left with one of a few options:
spm_parser
. (Yuck)rules_spm
to provide a repository rule that magically does the heavy lifting that it does today.rules_spm
. Instead of providing a repository rule, it would provide an executable target that generates Bazel build files similar to google/cargo-raze. (Thanks to @keith for making me aware of this project.)Created #157 asking the community how they would like to move forward.
Goals
https://github.com/grpc/grpc-swift
becomescom_github_grpc_grpc_swift
)Reasoning
148
86
Tasks
CSetting
).spm_parser
to a separate repository.rules_spm
to downloadspm_parser
.interesting_deps
example that useslibwebp
. exampleCSetting
).spm_parser
.build_mode
set tobazel
.Working Examples
simple
simple_with_dev_dir
simple_revision
interesting_deps
- Need to derive the source package name from the repo URL and not the pkg_name.simple_with_binary
- The binary that we define works. Theswiftformat
andswiftlint
do not work due to special C settings.ios_sim
- Requires support for special C settings.local_package
- Requires support for special C settings.public_hdrs
- Need to find source path frompath
setting in thePackage.swift
. (e.g. TrustKit)vapor
- Requires support for special C settings.