bazel-lib/docs/paths.md

Utilities for working with file paths.

relative_file

relative_file(to_file, frm_file)

Resolves a relative path between two files, "to_file" and "frm_file".

If neither of the paths begin with ../ it is assumed that they share the same root. When finding the relative path, the incoming files are treated as actual files (not folders) so the resulting relative path may differ when compared to passing the same arguments to python's "os.path.relpath()" or NodeJs's "path.relative()".

For example, 'relative_file("../foo/foo.txt", "bar/bar.txt")' will return '../../foo/foo.txt'

PARAMETERS

Name	Description	Default Value
to_file	the path with file name to resolve to, from frm	none
frm_file	the path with file name to resolve from	none

RETURNS

The relative path from frm_file to to_file, including the file name

to_output_relative_path

to_output_relative_path(file)

The relative path from bazel-out/[arch]/bin to the given File object

PARAMETERS

Name	Description	Default Value
file	a File object	none

RETURNS

The output relative path for the File

to_repository_relative_path

to_repository_relative_path(file)

The repository relative path for a File

This is the full runfiles path of a File excluding its workspace name.

This differs from root path (a.k.a. short_path) and rlocation path as it does not include the repository name if the File is from an external repository.

PARAMETERS

Name	Description	Default Value
file	a File object	none

RETURNS

The repository relative path for the File

to_rlocation_path

to_rlocation_path(ctx, file)

The rlocation path for a File

This produces the same value as the rlocationpath predefined source/output path variable.

From https://bazel.build/reference/be/make-variables#predefined_genrule_variables:

rlocationpath: The path a built binary can pass to the Rlocation function of a runfiles library to find a dependency at runtime, either in the runfiles directory (if available) or using the runfiles manifest.

This is similar to root path (a.k.a. short_path) in that it does not contain configuration prefixes, but differs in that it always starts with the name of the repository.

The rlocation path of a File in an external repository repo will start with repo/, followed by the repository-relative path.

Passing this path to a binary and resolving it to a file system path using the runfiles libraries is the preferred approach to find dependencies at runtime. Compared to root path, it has the advantage that it works on all platforms and even if the runfiles directory is not available.

PARAMETERS

Name	Description	Default Value
ctx	starlark rule execution context	none
file	a File object	none

RETURNS

The rlocationpath for the File