BUILD files

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Methods available in BUILD files. See also the Build Encyclopedia for extra functions and build rules, which can also be used in BUILD files.

Members

depset

depset depset(direct=None, order="default", *, transitive=None)

Creates a depset. The direct parameter is a list of direct elements of the depset, and transitive parameter is a list of depsets whose elements become indirect elements of the created depset. The order in which elements are returned when the depset is converted to a list is specified by the order parameter. See the Depsets overview for more information.

All elements (direct and indirect) of a depset must be of the same type, as obtained by the expression type(x).

Because a hash-based set is used to eliminate duplicates during iteration, all elements of a depset should be hashable. However, this invariant is not currently checked consistently in all constructors. Use the --incompatible_always_check_depset_elements flag to enable consistent checking; this will be the default behavior in future releases; see Issue 10313.

In addition, elements must currently be immutable, though this restriction will be relaxed in future.

The order of the created depset should be compatible with the order of its transitive depsets. "default" order is compatible with any other order, all other orders are only compatible with themselves.

Parameters

Parameter Description
direct sequence; or None; default is None
A list of direct elements of a depset.
order string; default is "default"
The traversal strategy for the new depset. See here for the possible values.
transitive sequence of depsets; or None; default is None
A list of depsets whose elements will become indirect elements of the depset.

existing_rule

unknown existing_rule(name)

Returns an immutable dict-like object that describes the attributes of a rule instantiated in this thread's package, or None if no rule instance of that name exists.

Here, an immutable dict-like object means a deeply immutable object x supporting dict-like iteration, len(x), name in x, x[name], x.get(name), x.items(), x.keys(), and x.values().

The result contains an entry for each attribute, with the exception of private ones (whose names do not start with a letter) and a few unrepresentable legacy attribute types. In addition, the dict contains entries for the rule instance's name and kind (for example, 'cc_binary').

The values of the result represent attribute values as follows:

  • Attributes of type str, int, and bool are represented as is.
  • Labels are converted to strings of the form ':foo' for targets in the same package or '//pkg:name' for targets in a different package.
  • Lists are represented as tuples, and dicts are converted to new, mutable dicts. Their elements are recursively converted in the same fashion.
  • select values are returned with their contents transformed as described above.
  • Attributes for which no value was specified during rule instantiation and whose default value is computed are excluded from the result. (Computed defaults cannot be computed until the analysis phase.).

If possible, avoid using this function. It makes BUILD files brittle and order-dependent. Also, beware that it differs subtly from the two other conversions of rule attribute values from internal form to Starlark: one used by computed defaults, the other used by ctx.attr.foo.

Parameters

Parameter Description
name string; required
The name of the target.

existing_rules

unknown existing_rules()

Returns an immutable dict-like object describing the rules so far instantiated in this thread's package. Each entry of the dict-like object maps the name of the rule instance to the result that would be returned by existing_rule(name).

Here, an immutable dict-like object means a deeply immutable object x supporting dict-like iteration, len(x), name in x, x[name], x.get(name), x.items(), x.keys(), and x.values().

Note: If possible, avoid using this function. It makes BUILD files brittle and order-dependent.

exports_files

None exports_files(srcs, visibility=None, licenses=None)

Specifies a list of files belonging to this package that are exported to other packages.

Parameters

Parameter Description
srcs sequence of strings; required
The list of files to export.
visibility sequence; or None; default is None
A visibility declaration can to be specified. The files will be visible to the targets specified. If no visibility is specified, the files will be visible to every package.
licenses sequence of strings; or None; default is None
Licenses to be specified.

glob

sequence glob(include=[], exclude=[], exclude_directories=1, allow_empty=unbound)

Glob returns a new, mutable, sorted list of every file in the current package that:
  • Matches at least one pattern in include.
  • Does not match any of the patterns in exclude (default []).
If the exclude_directories argument is enabled (set to 1), files of type directory will be omitted from the results (default 1).

Parameters

Parameter Description
include sequence of strings; default is []
The list of glob patterns to include.
exclude sequence of strings; default is []
The list of glob patterns to exclude.
exclude_directories int; default is 1
A flag whether to exclude directories or not.
allow_empty default is unbound
Whether we allow glob patterns to match nothing. If `allow_empty` is False, each individual include pattern must match something and also the final result must be non-empty (after the matches of the `exclude` patterns are excluded).

module_name

string module_name()

The name of the Bazel module associated with the repo this package is in. If this package is from a repo defined in WORKSPACE instead of MODULE.bazel, this is empty. For repos generated by module extensions, this is the name of the module hosting the extension. It's the same as the module.name field seen in module_ctx.modules. May return None.

module_version

string module_version()

The version of the Bazel module associated with the repo this package is in. If this package is from a repo defined in WORKSPACE instead of MODULE.bazel, this is empty. For repos generated by module extensions, this is the version of the module hosting the extension. It's the same as the module.version field seen in module_ctx.modules. May return None.

package

unknown package(**kwargs)

Declares metadata that applies to every rule in the package. It must be called at most once within a package (BUILD file). If called, it should be the first call in the BUILD file, right after the load() statements.

Parameters

Parameter Description
kwargs required
See the package() function in the Build Encyclopedia for applicable arguments.

package_group

None package_group(name, packages=[], includes=[])

This function defines a set of packages and assigns a label to the group. The label can be referenced in visibility attributes.

Parameters

Parameter Description
name string; required
The unique name for this rule.
packages sequence of strings; default is []
A complete enumeration of packages in this group.
includes sequence of strings; default is []
Other package groups that are included in this one.

package_name

string package_name()

The name of the package being evaluated, without the repository name. For example, in the BUILD file some/package/BUILD, its value will be some/package. If the BUILD file calls a function defined in a .bzl file, package_name() will match the caller BUILD file package.

package_relative_label

Label package_relative_label(input)

Converts the input string into a Label object, in the context of the package currently being initialized (that is, the BUILD file for which the current macro is executing). If the input is already a Label, it is returned unchanged.

This function may only be called while evaluating a BUILD file and the macros it directly or indirectly calls; it may not be called in (for instance) a rule implementation function.

The result of this function is the same Label value as would be produced by passing the given string to a label-valued attribute of a target declared in the BUILD file.

Usage note: The difference between this function and Label() is that Label() uses the context of the package of the .bzl file that called it, not the package of the BUILD file. Use Label() when you need to refer to a fixed target that is hardcoded into the macro, such as a compiler. Use package_relative_label() when you need to normalize a label string supplied by the BUILD file to a Label object. (There is no way to convert a string to a Label in the context of a package other than the BUILD file or the calling .bzl file. For that reason, outer macros should always prefer to pass Label objects to inner macros rather than label strings.)

Parameters

Parameter Description
input string; or Label; required
The input label string or Label object. If a Label object is passed, it's returned as is.

repo_name

string repo_name()

The canonical name of the repository containing the package currently being evaluated, with no leading at-signs.

repository_name

string repository_name()

Experimental. This API is experimental and may change at any time. Please do not depend on it. It may be enabled on an experimental basis by setting --+incompatible_enable_deprecated_label_apis
Deprecated. Prefer to use repo_name instead, which doesn't contain the spurious leading at-sign, but behaves identically otherwise.

The canonical name of the repository containing the package currently being evaluated, with a single at-sign (@) prefixed. For example, in packages that are called into existence by the WORKSPACE stanza local_repository(name='local', path=...) it will be set to @local. In packages in the main repository, it will be set to @.

select

unknown select(x, no_match_error='')

select() is the helper function that makes a rule attribute configurable. See build encyclopedia for details.

Parameters

Parameter Description
x dict; required
A dict that maps configuration conditions to values. Each key is a Label or a label string that identifies a config_setting or constraint_value instance. See the documentation on macros for when to use a Label instead of a string.
no_match_error string; default is ''
Optional custom error to report if no condition matches.

subpackages

sequence subpackages(include, exclude=[], allow_empty=False)

Returns a new mutable list of every direct subpackage of the current package, regardless of file-system directory depth. List returned is sorted and contains the names of subpackages relative to the current package. It is advised to prefer using the methods in bazel_skylib.subpackages module rather than calling this function directly.

Parameters

Parameter Description
include sequence of strings; required
The list of glob patterns to include in subpackages scan.
exclude sequence of strings; default is []
The list of glob patterns to exclude from subpackages scan.
allow_empty bool; default is False
Whether we fail if the call returns an empty list. By default empty list indicates potential error in BUILD file where the call to subpackages() is superflous. Setting to true allows this function to succeed in that case.