feat: expose common tar variables (#679)

lib/private/tar.bzl

@@ -1,5 +1,41 @@
 "Implementation of tar rule"
 
+TAR_TOOLCHAIN_TYPE = "@aspect_bazel_lib//lib:tar_toolchain_type"
+
+# https://www.gnu.org/software/tar/manual/html_section/Compression.html
+_ACCEPTED_EXTENSIONS = [
+ ".tar", # uncompressed,
+ ".gz", # gzip
+ ".tgz", # gzip
+ ".taz", # gzip
+ ".Z", # compress
+ ".taZ", # compress
+ ".bz2", # bzip2
+ ".tz2", # bzip2
+ ".tbz2", # bzip2
+ ".tbz", # bzip2
+ ".lz", # lzip
+ ".lzma", # lzma
+ ".tlz", # lzma
+ ".lzo", # lzop
+ ".xz", # xz
+ ".zst", # zstd
+ ".tzst", # zstd
+]
+
+# https://www.gnu.org/software/tar/manual/html_section/Compression.html
+_ACCEPTED_COMPRESSION_TYPES = [
+ "bzip2",
+ "compress",
+ "gzip",
+ "lrzip",
+ "lz4",
+ "lzma",
+ "lzop",
+ "xz",
+ "zstd",
+]
+
 _tar_attrs = {
  "args": attr.string_list(
  doc = "Additional flags permitted by BSD tar; see the man page.",
@@ -43,7 +79,7 @@ _tar_attrs = {
  ),
  "compress": attr.string(
  doc = "Compress the archive file with a supported algorithm.",
- values = ["bzip2", "compress", "gzip", "lrzip", "lz4", "lzma", "lzop", "xz", "zstd"],
+ values = _ACCEPTED_COMPRESSION_TYPES,
  ),
 }
 
@@ -52,7 +88,7 @@ _mtree_attrs = {
  "out": attr.output(doc = "Resulting specification file to write"),
 }
 
-def _add_compress_options(compress, args):
+def _add_compression_args(compress, args):
  if compress == "bzip2":
  args.add("--bzip2")
  if compress == "compress":
@@ -87,7 +123,7 @@ def _calculate_runfiles_dir(default_info):
  fail("manifest path {} seems malformed".format(manifest.short_path))
 
 def _tar_impl(ctx):
- bsdtar = ctx.toolchains["@aspect_bazel_lib//lib:tar_toolchain_type"]
+ bsdtar = ctx.toolchains[TAR_TOOLCHAIN_TYPE]
  inputs = ctx.files.srcs[:]
  args = ctx.actions.args()
 
@@ -98,7 +134,7 @@ def _tar_impl(ctx):
  args.add_all(ctx.attr.args)
 
  # Compression args
- _add_compress_options(ctx.attr.compress, args)
+ _add_compression_args(ctx.attr.compress, args)
 
  out = ctx.outputs.out or ctx.actions.declare_file(ctx.attr.name + ".tar")
  args.add("--file", out)
@@ -198,11 +234,17 @@ tar_lib = struct(
  implementation = _tar_impl,
  mtree_attrs = _mtree_attrs,
  mtree_implementation = _mtree_impl,
+ toolchain_type = TAR_TOOLCHAIN_TYPE,
+ common = struct(
+ accepted_tar_extensions = _ACCEPTED_EXTENSIONS,
+ accepted_compression_types = _ACCEPTED_COMPRESSION_TYPES,
+ add_compression_args = _add_compression_args,
+ ),
 )
 
 tar = rule(
  doc = "Rule that executes BSD `tar`. Most users should use the [`tar`](#tar) macro, rather than load this directly.",
  implementation = tar_lib.implementation,
  attrs = tar_lib.attrs,
- toolchains = ["@aspect_bazel_lib//lib:tar_toolchain_type"],
+ toolchains = [tar_lib.toolchain_type],
 )