unable to build a `csharp_proto_library` due to a toolchain-related error

[ltcmelo]

Issue Description

I'm unable to build a csharp_proto_library due to a toolchain-related error. I can reproduce this error with the csharp_proto_library example on the master branch.

csharp_proto_library git:(master) bazel build //:person_csharp_proto.dll
ERROR: /Users/ltcmelo/scm/rules_proto_grpc/example/csharp/csharp_proto_library/BUILD.bazel:3:21: While resolving toolchains for target //:person_csharp_proto.dll: no matching toolchains found for types @io_bazel_rules_dotnet//dotnet:toolchain_type_csharp_core
ERROR: Analysis of target '//:person_csharp_proto.dll' failed; build aborted:
INFO: Elapsed time: 0.092s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (0 packages loaded, 0 targets configured)

Building a csharp_proto_compile works, though.

csharp_proto_compile git:(master) bazel build //:person_csharp_proto
INFO: Analyzed target //:person_csharp_proto (0 packages loaded, 1 target configured).
INFO: Found 1 target...
Target //:person_csharp_proto up-to-date:
  bazel-bin/person_csharp_proto/Person.cs
INFO: Elapsed time: 0.130s, Critical Path: 0.00s
INFO: 1 process: 1 internal.
INFO: Build completed successfully, 1 total action

rules_proto_grpc Version

4.3.0 (and master)

Bazel Version

5.3.0

OS

macos (darwin arm64)

dotnet Version

6.0.101, 7.0.101, 7.0.202, and 7.0.203

[aaliddell]

To use the C# rules you need to manually specify the toolchains and platforms, for example:

bazel build --platforms=@io_bazel_rules_dotnet//dotnet/toolchain:linux_amd64_5.0.201 --host_platform=@io_bazel_rules_dotnet//dotnet/toolchain:linux_amd64_5.0.201 //:person_csharp_proto.dll

This is a requirement of rules_dotnet and isn't specific to rules_proto_grpc. It appears that recent rules_dotnet updates remove this mandatory toolchain specification, but that version is not currently used here. You could try overriding your rules_dotnet version in your WORKSPACE prior to loading rules_proto_grpc, but you'd be in untested territory.

[ltcmelo]

Thanks @aaliddell . Indeed, the current rules_dotnet allows you to register the desired dotnet toolchain in the WORKSPACE.

Yet, I tried --platforms and --host-platform as you suggest, and while works for a "pure C#" csharp_proto_library, it doesn't for a C# csharp_proto_library that depends on a proto_library.

proto_library(
    name = "lib",
    srcs = [a.proto],
    deps = ["@com_google_protobuf//..."],
    visibility = ["//visibility:public"],
)

csharp_proto_library(
    name = "other_lib.dll",
    protos = [b.proto],
    deps = ["//:lib"],
    visibility = ["//visibility:public"],
)

bazel build --platforms=@io_bazel_rules_dotnet//dotnet/toolchain:darwin_arm64_6.0.101 --host_platform=@io_bazel_rules_dotnet//dotnet/toolchain:darwin_arm64_6.0.101 //src/dotnet:other_lib.dll
ERROR: /src/dotnet/BUILD.bazel:55:21: in deps attribute of csharp_library rule //src/dotnet:other_lib.dll: '//:lib' does not have mandatory providers: 'DotnetLibraryInfo'. Since this rule was created by the macro 'csharp_proto_library', the error might have been caused by the macro implementation

But I'm not sure whether this error ☝🏽 is related to same issue; would you have an idea?

[ltcmelo]

It appears that I'm supposed to add "//:lib" to protos rather than to deps. Still, the deps from lib don't seem to be picked up (automatically), and if I add them to other_lib.dll, I'm "back" to the missing provider problem.