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Version: 1.24.x

expand_make_vars

Public API for expanding variables

Rules

expand_template

Template expansion

This performs a simple search over the template file for the keys in substitutions, and replaces them with the corresponding values.

Values may also use location templates as documented in expand_locations as well as configuration variables such as $(BINDIR), $(TARGET_CPU), and $(COMPILATION_MODE) as documented in expand_variables.

Example usage (generated):

load("@aspect_bazel_lib//lib:expand_make_vars.bzl", "expand_template")

expand_template(
# A unique name for this target.
name = "",
# Where to write the expanded file.
out = "",
# Mapping of strings to substitutions.
substitutions = {},
# The template file to expand.
template = "",
)

name

Required name.

A unique name for this target.

data

Optional list of labels. Default: []

List of targets for additional lookup information.

is_executable

Optional boolean. Default: False

Whether to mark the output file as executable.

out

Required label.

Where to write the expanded file.

substitutions

Required dictionary: String → String.

Mapping of strings to substitutions.

template

Required label.

The template file to expand.

Macros and Functions

expand_locations

Expand location templates.

Expands all $(execpath ...), $(rootpath ...) and deprecated $(location ...) templates in the given string by replacing with the expanded path. Expansion only works for labels that point to direct dependencies of this rule or that are explicitly listed in the optional argument targets.

See https://docs.bazel.build/versions/main/be/make-variables.html#predefined_label_variables.

Use $(rootpath) and $(rootpaths) to expand labels to the runfiles path that a built binary can use to find its dependencies. This path is of the format:

  • ./file
  • path/to/file
  • ../external_repo/path/to/file

Use $(execpath) and $(execpaths) to expand labels to the execroot (where Bazel runs build actions). This is of the format:

  • ./file
  • path/to/file
  • external/external_repo/path/to/file
  • <bin_dir>/path/to/file
  • <bin_dir>/external/external_repo/path/to/file

The deprecated $(location) and $(locations) expansions returns either the execpath or rootpath depending on the context.

Example usage (generated):

load("@aspect_bazel_lib//lib:expand_make_vars.bzl", "expand_locations")

expand_locations(
# context
ctx = None,
# String to be expanded
input = None,
)

ctx

Required.

context

input

Required.

String to be expanded

targets

Optional. Default: []

List of targets for additional lookup information.

expand_variables

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): ctx.label

  • $(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.

Example usage (generated):

load("@aspect_bazel_lib//lib:expand_make_vars.bzl", "expand_variables")

expand_variables(
# starlark rule context
ctx = None,
# expression to expand
s = None,
)

ctx

Required.

starlark rule context

s

Required.

expression to expand

outs

Optional. Default: []

declared outputs of the rule, for expanding references to outputs

output_dir

Optional. Default: False

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

Optional. Default: "args"

name of the attribute containing the expression. Used for error reporting.