refactor: infer the archive type from the filename

docs/testing.md

@@ -20,7 +20,7 @@ Assert that an archive file contains at least the given file entries.
 | <a id="assert_archive_contains-name"></a>name |  name of the resulting sh_test target   |  none |
 | <a id="assert_archive_contains-archive"></a>archive |  Label of the the .tar or .zip file   |  none |
 | <a id="assert_archive_contains-expected"></a>expected |  Label of a file containing a (partial) file listing   |  none |
-| <a id="assert_archive_contains-type"></a>type |  "tar" or "zip"   |  <code>"zip"</code> |
+| <a id="assert_archive_contains-type"></a>type |  "tar" or "zip". If None, a type will be inferred from the filename.   |  <code>None</code> |
 | <a id="assert_archive_contains-kwargs"></a>kwargs |  additional named arguments for the resulting sh_test   |  none |
 
 

lib/testing.bzl

@@ -114,19 +114,26 @@ def assert_json_matches(name, file1, file2, filter1 = ".", filter2 = "."):
         ),
     )
 
-def assert_archive_contains(name, archive, expected, type = "zip", **kwargs):
+def assert_archive_contains(name, archive, expected, type = None, **kwargs):
     """Assert that an archive file contains at least the given file entries.
 
     Args:
         name: name of the resulting sh_test target
         archive: Label of the the .tar or .zip file
         expected: Label of a file containing a (partial) file listing
-        type: "tar" or "zip"
+        type: "tar" or "zip". If None, a type will be inferred from the filename.
         **kwargs: additional named arguments for the resulting sh_test
     """
 
+    if not type:
+        if archive.endswith(".whl") or archive.endswith(".zip"):
+            type = "zip"
+        elif archive.endswith(".tar"):
+            type = "tar"
+        else:
+            fail("could not infer type from {}, please set the type attribute explicitly".format(archive))
     if not type in ["tar", "zip"]:
-        fail("type must be 'tar' or 'zip'")
+        fail("type must be 'tar' or 'zip', not " + type)
 
     # Command to list the files in the archive
     command = "zipinfo -1" if type == "zip" else "tar -tf"

lib/tests/assert_archive_contains/BUILD.bazel

@@ -10,5 +10,4 @@ assert_archive_contains(
     name = "check_tar",
     archive = "lib_tests.tar",
     expected = "expected_tar.txt",
-    type = "tar",
 )