Using data dependency for bazel ctx.action.run_shell custom rule - bazel

Question

I am looking at emit_rule example in bazel source tree:
https://github.com/bazelbuild/examples/blob/5a8696429e36090a75eb6fee4ef4e91a3413ef13/rules/shell_command/rules.bzl
I want to add a data dependency to the custom rule. My understanding of dependency attributes documentation calls for data attr label_list to be used, but it does not appear to work?
# This example copied from docs
def _emit_size_impl(ctx):
in_file = ctx.file.file
out_file = ctx.actions.declare_file("%s.pylint" % ctx.attr.name)
ctx.actions.run_shell(
inputs = [in_file],
outputs = [out_file],
command = "wc -c '%s' > '%s'" % (in_file.path, out_file.path),
)
return [DefaultInfo(files = depset([out_file]),)]
emit_size = rule(
implementation = _emit_size_impl,
attrs = {
"file": attr.label(mandatory = True,allow_single_file = True,),
"data": attr.label_list(allow_files = True),
# ^^^^^^^ Above does not appear to be sufficient to copy data dependency into sandbox
},
)
With this rule emit_size(name = "my_name", file = "my_file", data = ["my_data"]) I want to see my_data copied to bazel-out/ before running the command. How do I go about doing this?

Answer 1

The data files should be added as inputs to the actions that need those files, e.g. something like this:
def _emit_size_impl(ctx):
in_file = ctx.file.file
out_file = ctx.actions.declare_file("%s.pylint" % ctx.attr.name)
ctx.actions.run_shell(
inputs = [in_file] + ctx.files.data,
outputs = [out_file],
# For production rules, probably should use ctx.actions.run() and
# ctx.actions.args():
# https://bazel.build/rules/lib/Args
command = "echo data is: ; %s ; wc -c '%s' > '%s'" % (
"cat " + " ".join([d.path for d in ctx.files.data]),
in_file.path, out_file.path),
)
return [DefaultInfo(files = depset([out_file]),)]
emit_size = rule(
implementation = _emit_size_impl,
attrs = {
"file": attr.label(mandatory = True, allow_single_file = True,),
"data": attr.label_list(allow_files = True),
},
)
BUILD:
load(":defs.bzl", "emit_size")
emit_size(
name = "size",
file = "file.txt",
data = ["data1.txt", "data2.txt"],
)
$ bazel build size
INFO: Analyzed target //:size (4 packages loaded, 9 targets configured).
INFO: Found 1 target...
INFO: From Action size.pylint:
data is:
this is data
this is other data
Target //:size up-to-date:
bazel-bin/size.pylint
INFO: Elapsed time: 0.323s, Critical Path: 0.02s
INFO: 2 processes: 1 internal, 1 linux-sandbox.
INFO: Build completed successfully, 2 total actions
$ cat bazel-bin/size.pylint
22 file.txt