Extensions > API reference > Label


A BUILD target identifier.


Label Label(label_string, *, relative_to_caller_repository=False)

Creates a Label referring to a BUILD target. Use this function only when you want to give a default value for the label attributes. The argument must refer to an absolute label. Example:


Parameter Description
label_string ; required
the label string.
relative_to_caller_repository ; default = False
Deprecated. Do not use. When relative_to_caller_repository is True and the calling thread is a rule's implementation function, then a repo-relative label //foo:bar is resolved relative to the rule's repository. For calls to Label from any other thread, or calls in which the relative_to_caller_repository flag is False, a repo-relative label is resolved relative to the file in which the Label() call appears.


string Label.name

The name of this label within the package. For instance:
Label("//pkg/foo:abc").name == "abc"


string Label.package

The package part of this label. For instance:
Label("//pkg/foo:abc").package == "pkg/foo"


Label Label.relative(relName)

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")


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


string Label.workspace_name

The repository part of this label. For instance,
Label("@foo//bar:baz").workspace_name == "foo"


string Label.workspace_root

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