125 lines
4.0 KiB
Python
125 lines
4.0 KiB
Python
"""General-purpose rule to create tar archives.
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Unlike [pkg_tar from rules_pkg](https://github.com/bazelbuild/rules_pkg/blob/main/docs/latest.md#pkg_tar)
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this:
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- Does not depend on any Python interpreter setup
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- The "manifest" specification is a mature public API and uses a compact tabular format, fixing
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https://github.com/bazelbuild/rules_pkg/pull/238
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- Does not have any custom program to produce the output, instead
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we rely on a well-known C++ program called "tar".
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Specifically, we use the BSD variant of tar since it provides a means
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of controlling mtimes, uid, symlinks, etc.
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We also provide full control for tar'ring binaries including their runfiles.
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## Modifying metadata
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The `mtree_spec` rule can be used to create an mtree manifest for the tar file.
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Then you can mutate that spec, as it's just a simple text file, and feed the result
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as the `mtree` attribute of the `tar` rule.
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For example, to set the `uid` property, you could:
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```starlark
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mtree_spec(
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name = "mtree",
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srcs = ["//some:files"],
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)
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genrule(
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name = "change_owner",
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srcs = ["mtree"],
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outs = ["mtree.mutated"],
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cmd = "sed 's/uid=0/uid=1000/' <$< >$@",
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)
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tar(
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name = "tar",
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srcs = ["//some:files"],
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mtree = "change_owner",
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)
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```
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Note: We intend to contribute mutation features to https://github.com/vbatts/go-mtree
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to provide a richer API for things like `strip_prefix`.
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In the meantime, see the `lib/tests/tar/BUILD.bazel` file in this repo for examples.
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TODO:
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- Provide convenience for rules_pkg users to re-use or replace pkg_files trees
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"""
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load("@bazel_skylib//lib:types.bzl", "types")
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load("@bazel_skylib//rules:write_file.bzl", "write_file")
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load("//lib:utils.bzl", "propagate_common_rule_attributes")
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load("//lib/private:tar.bzl", _tar = "tar", _tar_lib = "tar_lib")
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mtree_spec = rule(
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doc = "Create an mtree specification to map a directory hierarchy. See https://man.freebsd.org/cgi/man.cgi?mtree(8)",
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implementation = _tar_lib.mtree_implementation,
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attrs = _tar_lib.mtree_attrs,
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)
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tar_rule = _tar
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tar_lib = _tar_lib
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def tar(name, mtree = "auto", **kwargs):
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"""Wrapper macro around [`tar_rule`](#tar_rule).
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Options for mtree
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-----------------
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mtree provides the "specification" or manifest of a tar file.
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See https://man.freebsd.org/cgi/man.cgi?mtree(8)
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Because BSD tar doesn't have a flag to set modification times to a constant,
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we must always supply an mtree input to get reproducible builds.
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See https://reproducible-builds.org/docs/archives/ for more explanation.
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1. By default, mtree is "auto" which causes the macro to create an `mtree_spec` rule.
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2. `mtree` may be supplied as an array literal of lines, e.g.
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```
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mtree =[
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"usr/bin uid=0 gid=0 mode=0755 type=dir",
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"usr/bin/ls uid=0 gid=0 mode=0755 time=0 type=file content={}/a".format(package_name()),
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],
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```
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For the format of a line, see "There are four types of lines in a specification" on the man page for BSD mtree,
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https://man.freebsd.org/cgi/man.cgi?mtree(8)
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3. `mtree` may be a label of a file containing the specification lines.
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Args:
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name: name of resulting `tar_rule`
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mtree: "auto", or an array of specification lines, or a label of a file that contains the lines.
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**kwargs: additional named parameters to pass to `tar_rule`
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"""
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mtree_target = "_{}.mtree".format(name)
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if mtree == "auto":
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mtree_spec(
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name = mtree_target,
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srcs = kwargs["srcs"],
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out = "{}.txt".format(mtree_target),
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**propagate_common_rule_attributes(kwargs)
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)
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elif types.is_list(mtree):
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write_file(
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name = mtree_target,
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out = "{}.txt".format(mtree_target),
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# Ensure there's a trailing newline, as bsdtar will ignore a last line without one
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content = mtree + [""],
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newline = "unix",
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**propagate_common_rule_attributes(kwargs)
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)
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else:
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mtree_target = mtree
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tar_rule(
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name = name,
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mtree = mtree_target,
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**kwargs
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)
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