Disable use of tar command in test on macOS.

tar / gzip output isn't reproducible on macOS at the moment so only
run reproducibility tests with tarfile on macOS.

Change-Id: Ib984d86ff611ec76aa39cded0ed67cedd087995a

Author: Stewart Miles

source/ExportUnityPackage/export_unity_package.py

@@ -281,6 +281,10 @@
 flags.DEFINE_string("guids_file", None, "Json file with stable guids cache.")
 flags.DEFINE_string("plugins_version", None, "Version of the plugins to "
                     "package.")
+flags.DEFINE_boolean("use_tar", True, "Whether to use the tar command line "
+                     "application, when available, to generate archives rather "
+                     "than Python's tarfile module.  NOTE: On macOS tar / gzip "
+                     "generate Unity compatible but non-reproducible archives.")
 flags.DEFINE_boolean(
     "enforce_semver", True, "Whether to enforce semver (major.minor.patch) for"
     "plugins_version.  This is required to build UPM package.")
@@ -2479,7 +2483,7 @@ def create_archive(archive_filename, input_directory, timestamp):
                        platform.system() == "Darwin")
       gnu_tar_available = platform.system() == "Linux"
       # Whether a reproducible tar.gz is required.
-      if tar_available:
+      if tar_available and FLAGS.use_tar:
         # tarfile is 10x slower than the tar command so use the command line
         # tool where it's available and can generate a reproducible archive.
         list_filename = os.path.join(tempfile.mkdtemp(), "input_files.txt")

source/ExportUnityPackage/export_unity_package_test.py

@@ -20,11 +20,13 @@
 import filecmp
 import json
 import os
+import platform
 import re
 import shutil
 import stat
 import sys
 import tarfile
+import time
 from absl import flags
 from absl.testing import absltest
 
@@ -2618,7 +2620,12 @@ def test_package_create_archive(self):
     """Create a unitypackage archive."""
     test_case_dir = os.path.join(FLAGS.test_tmpdir, "test_create_archive")
     os.makedirs(test_case_dir)
+    use_tar = export_unity_package.FLAGS.use_tar
     try:
+      # Disable use of tar command line application until this is reproducible on
+      # macOS.
+      export_unity_package.FLAGS.use_tar = (platform.system() != "Darwin")
+
       archive_dir = os.path.join(test_case_dir, "archive_dir")
       os.makedirs(archive_dir)
       # Create some files to archive.
@@ -2655,6 +2662,9 @@ def test_package_create_archive(self):
       other_archive_filename = os.path.join(test_case_dir,
                                             "archive2.unitypackage")
       os.rename(archive_filename, other_archive_filename)
+      # Wait before writing another archive so that any potential changes to
+      # timestamps can be written.
+      time.sleep(1)
       # We create the archive with the original filename as the filename is
       # embedded in the archive.
       export_unity_package.PackageConfiguration.create_archive(archive_filename,
@@ -2663,6 +2673,7 @@ def test_package_create_archive(self):
 
     finally:
       shutil.rmtree(test_case_dir)
+      export_unity_package.FLAGS.use_tar = use_tar
 
   def test_package_write(self):
     """Write a .unitypackage file."""