expand_make_vars

Public API for expanding variables

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.

Bazel pre-defined variables are expanded however only $@, $(@D) and $(RULEDIR) of pre-defined genrule variables are supported.

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

attribute_name

Optional. Default: "args"

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