When writing custom rules, you often need to invoke executables with
argument lists. For example, let’s say you are writing a custom rule
that executes gcc to compile a set of input source files. You
could write:
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output_file = ctx.actions.declare_file("exe")
ctx.actions.run(
inputs = ctx.files.srcs,
outputs = [output_file],
# This is for demo purposes. In a real Bazel rule you'd# want to use cc_common.
executable ="/usr/bin/gcc",
arguments = ["-o", output_file.path] + [x.path for x in ctx.files.srcs],
)
However, it is both more efficient and better style to create the
arguments list using ctx.actions.args(). Furthermore, the
args object will automatically handle any
path vs short_path differences for you.
Therefore, the above rule fragment should instead be written as:
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output_file = ctx.actions.declare_file("exe")
args = ctx.actions.args()
args.add("-o", output_file)
args.add_all(ctx.files.srcs)
ctx.actions.run(
inputs = ctx.files.srcs,
outputs = [output_file],
# This is for demo purposes. In a real Bazel rule you'd# want to use cc_common.
executable ="/usr/bin/gcc",
arguments = [args],
)
