bazel-lib/lib/private/expand_variables.bzl

94 lines
3.7 KiB
Python

"Helpers to expand make variables"
load("@bazel_skylib//lib:paths.bzl", _spaths = "paths")
def expand_variables(ctx, s, outs = [], output_dir = False, attribute_name = "args"):
"""Expand make variables and substitute like genrule does.
This function is the same as ctx.expand_make_variables with the additional
genrule-like substitutions of:
- `$@`: The output file if it is a single file. Else triggers a build error.
- `$(@D)`: The output directory.
If there is only one file name in outs, this expands to the directory containing that file.
If there is only one directory in outs, this expands to the single output directory.
If there are multiple files, this instead expands to the package's root directory in the bin tree,
even if all generated files belong to the same subdirectory!
- `$(RULEDIR)`: The output directory of the rule, that is, the directory
corresponding to the name of the package containing the rule under the bin tree.
- $(BUILD_FILE_PATH)": ctx.build_file_path
- $(VERSION_FILE)": ctx.version_file.path
- $(INFO_FILE)": ctx.info_file.path
- $(TARGET)": "@%s//%s:%s" % (ctx.label.workspace_name, ctx.label.package, ctx.label.name)
- $(WORKSPACE)": ctx.workspace_name
See https://docs.bazel.build/versions/main/be/general.html#genrule.cmd and
https://docs.bazel.build/versions/main/be/make-variables.html#predefined_genrule_variables
for more information of how these special variables are expanded.
Args:
ctx: starlark rule context
s: expression to expand
outs: declared outputs of the rule, for expanding references to outputs
output_dir: whether the rule is expected to output a directory (TreeArtifact)
Deprecated. For backward compatability with @aspect_bazel_lib 1.x. Pass
output tree artifacts to outs instead.
attribute_name: name of the attribute containing the expression. Used for error reporting.
Returns:
`s` with the variables expanded
"""
rule_dir = _spaths.join(
ctx.bin_dir.path,
ctx.label.workspace_root,
ctx.label.package,
)
additional_substitutions = {}
# TODO(2.0): remove output_dir in 2.x release
if output_dir:
if s.find("$@") != -1 or s.find("$(@)") != -1:
fail("$@ substitution may only be used with output_dir=False.")
# We'll write into a newly created directory named after the rule
output_dir = _spaths.join(
ctx.bin_dir.path,
ctx.label.workspace_root,
ctx.label.package,
ctx.label.name,
)
else:
if s.find("$@") != -1 or s.find("$(@)") != -1:
if len(outs) > 1:
fail("$@ substitution may only be used with a single out.")
if len(outs) == 1:
additional_substitutions["@"] = outs[0].path
if outs[0].is_directory:
output_dir = outs[0].path
else:
output_dir = outs[0].dirname
else:
output_dir = rule_dir
additional_substitutions["@D"] = output_dir
additional_substitutions["RULEDIR"] = rule_dir
# Add some additional make variable substitutions for common useful values in the context
additional_substitutions["BUILD_FILE_PATH"] = ctx.build_file_path
additional_substitutions["VERSION_FILE"] = ctx.version_file.path
additional_substitutions["INFO_FILE"] = ctx.info_file.path
additional_substitutions["TARGET"] = "@%s//%s:%s" % (ctx.label.workspace_name, ctx.label.package, ctx.label.name)
additional_substitutions["WORKSPACE"] = ctx.workspace_name
return ctx.expand_make_variables(attribute_name, s, additional_substitutions)