swift_c_module "does not have mandatory providers: 'cc'" with bazel 0.22

[keith]

With the bazel 0.22rc2 pre-release (from here), with this WORKSPACE:

http_archive(
    name = "StringsGenPathKit",
    build_file = "//bazel/third_party:PathKit.BUILD",
    sha256 = "463c5a14204991e9b82c397f426be79756d8c305555e11c572e88ec2e2ab374b",
    strip_prefix = "PathKit-0.9.1",
    url = "https://github.com/kylef/PathKit/archive/0.9.1.tar.gz",
)

http_archive(
    name = "StringsGenYams",
    build_file = "//bazel/third_party:Yams.BUILD",
    patch_cmds = [
        """
echo '
module CYaml {
    umbrella header "CYaml.h"
    export *
}
' > Sources/CYaml/include/Yams.modulemap
    """,
    ],
    sha256 = "c58ed6520b35a83b3998f076b61134c5456d9349006ec1300744db903b3086f4",
    strip_prefix = "Yams-0.7.0",
    url = "https://github.com/jpsim/Yams/archive/0.7.0.tar.gz",
)

And this in the BUILD file:

load(
    "@build_bazel_rules_swift//swift:swift.bzl",
    "swift_c_module",
    "swift_library",
)

cc_library(
    name = "CYamlLib",
    srcs = glob([
        "Sources/CYaml/src/*.c",
        "Sources/CYaml/src/*.h",
    ]),
    hdrs = glob([
        "Sources/CYaml/include/*.h",
    ]),
    includes = ["Sources/CYaml/include"],
    linkstatic = True,
)

swift_c_module(
    name = "CYaml",
    module_map = "Sources/CYaml/include/Yams.modulemap",
    deps = [":CYamlLib"],
)

swift_library(
    name = "Yams",
    srcs = glob(["Sources/Yams/*.swift"]),
    cc_libs = [":CYamlLib"],
    copts = ["-whole-module-optimization"],
    defines = ["SWIFT_PACKAGE"],
    visibility = ["//visibility:public"],
    deps = [":CYaml"],
)

I end up with this build error:

ERROR: /private/var/tmp/_bazel_ksmiley/c8513c989333be3c89713e16206869b2/external/StringsGenYams/BUILD.bazel:23:12: in deps attribute of swift_c_module rule @StringsGenYams//:CYaml: '@StringsGenYams//:CYamlLib' does not have mandatory providers: 'cc'
ERROR: Analysis of target '//Modules/PassengerCore:PassengerCore' failed; build aborted: Analysis of target '@StringsGenYams//:CYaml' failed; build aborted

I'm not sure what change in bazel has caused this yet

[allevato]

I believe it's this: bazelbuild/bazel@a60b6ce

There have been a number of changes to the C++ providers recently that I've been waiting to become finalized enough that I can adopt them.

[keith]

Confirmed that setting --no incompatible_disable_legacy_cc_provider works around this

[keith]

Is this something we can migrate now? Or would we have to support both at once? I haven't looked for when the new providers were added

[keith]

It looks like the same conversation is happening here bazelbuild/bazel#7036 (comment)

[keith]

@allevato is this something you're planning on working on before the 0.22 release?

[allevato]

I'll start working on the migration this week, but the currently released version of Bazel that we use internally doesn't yet include the above commit yet, so I can't release anything until we catch up to that.

I looked into support both simultaneously, but the effort would be fairly large since the old- and new-style providers are very different, and I can't rationalize that amount of effort for a short-term workaround.

If Bazel releases 0.22 before I'm able to fully test the change internally and push it out, then I'd recommend using --noincompatible_disable_legacy_cc_provider until rules_swift can be updated.

[keith]

I've commented on the linked issue asking about the migration window, it doesn't seem like 0.22 has the necessary files I expected. I've submitted a first pass PR for this that is compatible with bazel HEAD right now #129

[keith]

My PR is green now so we should be good for compatibility with 0.22!

[allevato]

I believe this is resolved now.