How to track source of rules (functions) in bazel? Is there any order of initialisation or query to-CodePudding

How to find places where the rule is defined and which definition bazel uses in this specific package?

Say, I have gRPC installed and looking at grpc/examples/cpp/helloword/BUILD file. I can see a common rule for cpp builds: cc_binary. But this rule is not in grpc WORKSPACE file. Nor it in BUILD file. I do grep -rnw -e '"cc_binary"' and can't find it anywhere but /grpc/third_party/.. subdirectories. And this wouldn't make any sense for bazel to initiate this rule there.

I do finding the dependencies of a rule bazel query "deps(//examples/cpp/helloworld:cc_binary)" and strangely, it doesn't want to query the rules - only targets. I get:

ERROR: no such target '//examples/cpp/helloworld:cc_binary': target 'cc_binary' not declared in package 'examples/cpp/helloworld'

When I do bazel query 'kind(cc_binary, deps(//examples/cpp/helloworld:greeter_client))' I think I'm getting closer with this list:

//examples/cpp/helloworld:greeter_client
@upb//upbc:protoc-gen-upbdefs
@upb//upbc:protoc-gen-upb
@com_google_protobuf//:protoc
//src/compiler:grpc_cpp_plugin
@bazel_tools//third_party/def_parser:def_parser

But how can it help me? Is there a way to do it?

CodePudding user response：

In general, query --output=build will emit a comment indicating where a target's rule class is defined:

$ bazel query --output build //src/proto/grpc/core:stats_py_pb2
py_proto_library(
  name = "stats_py_pb2",
  deps = ["//src/proto/grpc/core:stats_descriptor"],
)
# Rule stats_py_pb2 instantiated at (most recent call last):
#   grpc/src/proto/grpc/core/BUILD:35:17 in <toplevel>
# Rule py_proto_library defined at (most recent call last):
#   grpc/bazel/python_rules.bzl:154:24 in <toplevel>

cc_binary is a builtin rule, implemented in Java within Bazel. Therefore, Bazel cannot provide a Starlark source for its definition:

$ bazel query --output build //examples/cpp/helloworld:greeter_client
cc_binary(
  name = "greeter_client",
  deps = ["//:grpc  ", "//examples/protos:helloworld_cc_grpc"],
  defines = ["BAZEL_BUILD"],
  srcs = ["//examples/cpp/helloworld:greeter_client.cc"],
)
# Rule greeter_client instantiated at (most recent call last):
#   grpc/examples/cpp/helloworld/BUILD:17:10 in <toplevel>