bazel-lib/docs/copy_directory.md

A rule that copies a directory to another place.

The rule uses a precompiled binary to perform the copy, so no shell is required.

Preserving modification times

copy_directory and copy_to_directory have a preserve_mtime attribute, however there are two caveats to consider when using this feature:

1. Remote Execution / Caching: These layers will reset the modify time and are incompatible with this feature. To avoid these failures the no-remote tag can be added.
2. Caching: Changes to only the modified time will not re-trigger cached actions. This can be worked around by using a clean build when these types of changes occur. For tests the external tag can be used but this will result in tests never being cached.

copy_directory

copy_directory(name, src, out, hardlink, kwargs)

Copies a directory to another location.

This rule uses a precompiled binary to perform the copy, so no shell is required.

If using this rule with source directories, it is recommended that you use the --host_jvm_args=-DBAZEL_TRACK_SOURCE_DIRECTORIES=1 startup option so that changes to files within source directories are detected. See c64421bc35 for more context.

PARAMETERS

Name	Description	Default Value
name	Name of the rule.	none
src	The directory to make a copy of. Can be a source directory or TreeArtifact.	none
out	Path of the output directory, relative to this package.	none
hardlink	Controls when to use hardlinks to files instead of making copies. Creating hardlinks is much faster than making copies of files with the caveat that hardlinks share file permissions with their source. Since Bazel removes write permissions on files in the output tree after an action completes, hardlinks to source files within source directories is not recommended since write permissions will be inadvertently removed from sources files. - "auto": hardlinks are used if src is a tree artifact already in the output tree - "off": files are always copied - "on": hardlinks are always used (not recommended)	"auto"
kwargs	further keyword arguments, e.g. visibility	none

copy_directory_bin_action

copy_directory_bin_action(ctx, src, dst, copy_directory_bin, copy_directory_toolchain, hardlink,
                          verbose, preserve_mtime)

Factory function that creates an action to copy a directory from src to dst using a tool binary.

The tool binary will typically be the @aspect_bazel_lib//tools/copy_directory go_binary either built from source or provided by a toolchain.

This helper is used by the copy_directory rule. It is exposed as a public API so it can be used within other rule implementations.

PARAMETERS

Name	Description	Default Value
ctx	The rule context.	none
src	The source directory to copy.	none
dst	The directory to copy to. Must be a TreeArtifact.	none
copy_directory_bin	Copy to directory tool binary.	none
copy_directory_toolchain	The toolchain type for Auto Exec Groups. The default is probably what you want.	"@aspect_bazel_lib//lib:copy_directory_toolchain_type"
hardlink	Controls when to use hardlinks to files instead of making copies. See copy_directory rule documentation for more details.	"auto"
verbose	print verbose logs to stdout	False
preserve_mtime	preserve the modified time from the source. See the caveats above about interactions with remote execution and caching.	False