You can get this information by using bazel aquery to query
the action graph.
Here’s a slightly richer example, with two output files from a single
genrule:
$ ls
BUILD main.in WORKSPACE
$ cat WORKSPACE
$ cat BUILD
genrule(
name = "main",
srcs = ["main.in"],
outs = ["main.o1", "main.o2"],
cmd = "cp $< $(location main.o1); cp $< $(location main.o2)",
)
$ cat main.in
hello
Use bazel aquery //:main --output=textproto to query the action graph with machine-readable output (the proto is analysis.ActionGraphContainer):
$ bazel aquery //:main --output=textproto >aquery_result 2>/dev/null
$ cat aquery_result
artifacts {
id: "0"
exec_path: "main.in"
}
artifacts {
id: "1"
exec_path: "external/bazel_tools/tools/genrule/genrule-setup.sh"
}
artifacts {
id: "2"
exec_path: "bazel-out/k8-fastbuild/genfiles/main.o1"
}
artifacts {
id: "3"
exec_path: "bazel-out/k8-fastbuild/genfiles/main.o2"
}
actions {
target_id: "0"
action_key: "dd7fd759bbecce118a399c6ce7b0c4aa"
mnemonic: "Genrule"
configuration_id: "0"
arguments: "/bin/bash"
arguments: "-c"
arguments: "source external/bazel_tools/tools/genrule/genrule-setup.sh; cp main.in bazel-out/k8-fastbuild/genfiles/main.o1; cp main.in bazel-out/k8-fastbuild/genfiles/main.o2"
input_dep_set_ids: "0"
output_ids: "2"
output_ids: "3"
}
targets {
id: "0"
label: "//:main"
rule_class_id: "0"
}
dep_set_of_files {
id: "0"
direct_artifact_ids: "0"
direct_artifact_ids: "1"
}
configuration {
id: "0"
mnemonic: "k8-fastbuild"
platform_name: "k8"
}
rule_classes {
id: "0"
name: "genrule"
}
The data isn’t exactly all in one place, but note that:
- the artifacts with IDs
2 and 3 correspond to our two desired
output files, and list the output locations of those artifacts as
paths to files on disk relative to your workspace root;
- the
artifacts entry with target ID 0 is associated with artifact
IDs 2 and 3; and
- the
targets entry with ID "0" is associated with the //:main
label.
Given this simple structure, we can easily whip together a script to
list all output files corresponding to a provided label. I can’t find a
way to depend directly on Bazel’s definition of analysis.proto or its
language bindings from an external repository, so you can patch the
following script into the bazelbuild/bazel repository itself:
tools/list_outputs/list_outputs.py
# Copyright 2019 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
r"""Parse an `aquery` result to list outputs created for a target.
Use this binary in conjunction with `bazel aquery` to determine the
paths on disk to output files of a target.
Example usage: first, query the action graph for the target that you
want to analyze:
bazel aquery //path/to:target --output=textproto >/tmp/aquery_result
Then, from the Bazel repository:
bazel run //tools/list_outputs -- \
--aquery_result /tmp/aquery_result \
--label //path/to:target \
;
This will print a list of zero or more output files emitted by the given
target, like:
bazel-out/k8-fastbuild/foo.genfile
bazel-out/k8-fastbuild/bar.genfile
If the provided label does not appear in the output graph, an error will
be raised.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import sys
from absl import app
from absl import flags
from google.protobuf import text_format
from src.main.protobuf import analysis_pb2
flags.DEFINE_string(
"aquery_result",
None,
"Path to file containing result of `bazel aquery ... --output=textproto`.",
)
flags.DEFINE_string(
"label",
None,
"Label whose outputs to print.",
)
def die(message):
sys.stderr.write("fatal: %s\n" % (message,))
sys.exit(1)
def main(unused_argv):
if flags.FLAGS.aquery_result is None:
raise app.UsageError("Missing `--aquery_result` argument.")
if flags.FLAGS.label is None:
raise app.UsageError("Missing `--label` argument.")
if flags.FLAGS.aquery_result == "-":
aquery_result = sys.stdin.read()
else:
with open(flags.FLAGS.aquery_result) as infile:
aquery_result = infile.read()
label = flags.FLAGS.label
action_graph_container = analysis_pb2.ActionGraphContainer()
text_format.Merge(aquery_result, action_graph_container)
matching_targets = [
t for t in action_graph_container.targets
if t.label == label
]
if len(matching_targets) != 1:
die(
"expected exactly one target with label %r; found: %s"
% (label, sorted(t.label for t in matching_targets))
)
target = matching_targets[0]
all_artifact_ids = frozenset(
artifact_id
for action in action_graph_container.actions
if action.target_id == target.id
for artifact_id in action.output_ids
)
for artifact in action_graph_container.artifacts:
if artifact.id in all_artifact_ids:
print(artifact.exec_path)
if __name__ == "__main__":
app.run(main)
tools/list_outputs/BUILD
# Copyright 2019 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
package(default_visibility = ["//visibility:public"])
licenses(["notice"]) # Apache 2.0
filegroup(
name = "srcs",
srcs = glob(["**"]),
)
py_binary(
name = "list_outputs",
srcs = ["list_outputs.py"],
srcs_version = "PY2AND3",
deps = [
"//third_party/py/abseil",
"//src/main/protobuf:analysis_py_proto",
],
)
As a Git patch, for your convenience:
https://gist.github.com/wchargin/5e6a43a203d6c95454aae2886c5b54e4
Please note that this code hasn’t been reviewed or verified for
correctness; I provide it primarily as an example. If it’s useful to
you, then maybe this weekend I can write some tests for it and PR it
against Bazel itself.
