Label

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A BUILD target identifier.

For every Label instance l, the string representation str(l) has the property that Label(str(l)) == l, regardless of where the Label() call occurs.

When passed as positional arguments to print() or fail(), Label use a string representation optimized for human readability instead. This representation uses an apparent repository name from the perspective of the main repository if possible.

Members

Label

Label Label(input)

Converts a label string into a Label object, in the context of the package where the calling .bzl source file lives. If the given value is already a Label, it is returned unchanged.

For macros, a related function, native.package_relative_label(), converts the input into a Label in the context of the package currently being constructed. Use that function to mimic the string-to-label conversion that is automatically done by label-valued rule attributes.

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.

name

string Label.name

The name of the target referred to by this label. For instance:
Label("@@foo//pkg/foo:abc").name == "abc"

package

string Label.package

The name of the package containing the target referred to by this label, without the repository name. For instance:
Label("@@repo//pkg/foo:abc").package == "pkg/foo"

relative

Label Label.relative(relName)

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. This method behaves surprisingly when used with an argument containing an apparent repo name. Prefer Label.same_package_label(), native.package_relative_label(), or Label() instead.

Resolves a label that is either absolute (starts with //) or relative to the current package. If this label is in a remote repository, the argument will be resolved relative to that repository. If the argument contains a repository name, the current label is ignored and the argument is returned as-is, except that the repository name is rewritten if it is in the current repository mapping. Reserved labels will also be returned as-is.
For example:

Label("//foo/bar:baz").relative(":quux") == Label("//foo/bar:quux")
Label("//foo/bar:baz").relative("//wiz:quux") == Label("//wiz:quux")
Label("@repo//foo/bar:baz").relative("//wiz:quux") == Label("@repo//wiz:quux")
Label("@repo//foo/bar:baz").relative("//visibility:public") == Label("//visibility:public")
Label("@repo//foo/bar:baz").relative("@other//wiz:quux") == Label("@other//wiz:quux")

If the repository mapping passed in is {'@other' : '@remapped'}, then the following remapping will take place:

Label("@repo//foo/bar:baz").relative("@other//wiz:quux") == Label("@remapped//wiz:quux")

Parameters

Parameter Description
relName string; required
The label that will be resolved relative to this one.

repo_name

string Label.repo_name

The canonical name of the repository containing the target referred to by this label, without any leading at-signs (@). For instance,
Label("@@foo//bar:baz").repo_name == "foo"

same_package_label

Label Label.same_package_label(target_name)

Creates a label in the same package as this label with the given target name.

Parameters

Parameter Description
target_name string; required
The target name of the new label.

workspace_name

string Label.workspace_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. The field name "workspace name" is a misnomer here; use the identically-behaving Label.repo_name instead.

The canonical name of the repository containing the target referred to by this label, without any leading at-signs (@). For instance,

Label("@@foo//bar:baz").workspace_name == "foo"

workspace_root

string Label.workspace_root

Returns the execution root for the repository containing the target referred to by this label, relative to the execroot. For instance:
Label("@repo//pkg/foo:abc").workspace_root == "external/repo"