What Argon's read of #540 left: the unpack cap's exact bound, the redirect row, and the Head tests run as a file

adapters/AGENTS.md

@@ -10,7 +10,7 @@ Not built yet, by the stories that hold their rules: contract.py, binding.py, is
 | Only `github.py` imports what reaches the network, or names the storage | `tests/test_tools.py::test_only_the_transport_reaches_the_network`, `tests/test_tools.py::test_only_the_transport_names_githubs_artifact_storage` |
 | It sends HTTPS to GitHub's API alone, by a path from its root | `tests/test_adapters.py::test_a_request_stays_on_githubs_api` |
 | It follows no redirect but an artifact's download and a tarball's (0138), takes no proxy, bounds every answer, and uses its caller's token | `tests/test_adapters.py::test_the_live_transport_takes_its_token_from_its_caller_and_follows_no_redirect` |
-| An artifact's download alone follows its redirect, to GitHub's artifact storage alone, over HTTPS | `tests/test_adapters.py::test_only_an_artifacts_download_follows_its_redirect_and_only_to_githubs_storage` |
+| An artifact's download follows its redirect to GitHub's artifact storage alone, over HTTPS | `tests/test_adapters.py::test_only_an_artifacts_download_follows_its_redirect_and_only_to_githubs_storage` |
 | No token is sent to the storage, and what it answers is bounded | `tests/test_adapters.py::test_the_live_transport_sends_no_token_to_the_storage_and_bounds_what_it_holds` |
 | A download is bounded at 64 KiB, 1 MiB for a pass record, read out to 8 MiB; a Run's record is found by its pass id | `tests/test_adapters.py::test_a_pass_record_alone_is_downloaded_under_a_wider_bound`, `tests/test_steps.py::test_a_runs_record_is_found` |
 | The last two passes' records are read, this pass's run passed over; what cannot be read is none, never fewer | `tests/test_adapters.py::test_the_last_two_pass_records_are_read`, `tests/test_adapters.py::test_unreadable_pass_records_are_none` |

tests/test_harness.py

@@ -1093,9 +1093,6 @@ def test_the_cli_starts_in_an_empty_directory_with_only_its_environment(self):
         self.assertEqual(done.stdout, "\ufffd{")
 
 
-if __name__ == "__main__":
-    unittest.main()
-
 
 def resummed(header: bytes, at: int, value: bytes) -> bytes:
     """A tar header with `value` at `at`, its checksum made its own again."""
@@ -1108,7 +1105,9 @@ def resummed(header: bytes, at: int, value: bytes) -> bytes:
 
 class Head(unittest.TestCase):
     """`harness/head.py`: a pull request's head read as its tarball and written by hand, member by member, into a folder
-    of its own (decision 0138). Each archive it refuses, it refuses whole, by the check that names why."""
+    of its own (decision 0138). Each archive it refuses, it refuses at the first check that fails, by the check that names
+    why; what it wrote before that is its caller's to remove, as `harness/read.py` removes it
+    (`tests/test_steps.py`'s cases of `head_unreadable`)."""
 
     SHA = "9f1c2d3e4b5a69788796a5b4c3d2e1f0a9b8c7d6"
 
@@ -1254,6 +1253,13 @@ def test_the_unpacker_holds_its_caps_and_writes_nothing_outside_its_folder(self)
                          "more than 4 members")
             head.MEMBERS, head.UNPACKED = original[0], 4096
             self.refused(support.tarball(sha, [("big", b"0", b"x" * 5000)]), "more than 4096 bytes")
+            # The cap is on the whole archive unpacked, every member's header and padding among it: one of exactly that
+            # many bytes is written, and one byte fewer allowed refuses it (Argon's read of #540).
+            data = support.tarball(sha, [("a", b"0", b"x" * 2048), ("b", b"0", b"x" * 2049)])
+            head.UNPACKED = len(zlib.decompress(data, 16 + zlib.MAX_WBITS))
+            self.unpacked(data)
+            head.UNPACKED -= 1
+            self.refused(data, "more than %d bytes" % head.UNPACKED)
         finally:
             head.MEMBERS, head.UNPACKED = original
         # The folder is new: one that stands already is never written into.
@@ -1400,3 +1406,7 @@ def body(*entries, truncated=False):
                     self.assertIsInstance(err, head.Refused)
                 else:
                     self.fail("read, not refused")
+
+
+if __name__ == "__main__":
+    unittest.main()

tools/mutants.py

@@ -7096,6 +7096,9 @@ def moved_before(rel: str, block: str, anchor: str) -> tuple:
     ('a tarball not answered is unpacked', 'harness/head.py',
      '    if answer.get("status") != 200 or not isinstance(answer.get("body"), str):',
      '    if not isinstance(answer.get("body"), str):', ('tests.test_harness.Head.test_the_head_of_p60_is_unpacked_as_codeload_served_it',)),
+    ('an archive of exactly the cap is refused', 'harness/head.py',
+     '    if len(tar) > UNPACKED or unzip.unconsumed_tail:',
+     '    if len(tar) >= UNPACKED or unzip.unconsumed_tail:', ('tests.test_harness.Head.test_the_unpacker_holds_its_caps_and_writes_nothing_outside_its_folder',)),
     ('an archive over the cap is cut short and read', 'harness/head.py',
      '    if len(tar) > UNPACKED or unzip.unconsumed_tail:',
      '    if False:', ('tests.test_harness.Head.test_the_unpacker_holds_its_caps_and_writes_nothing_outside_its_folder',)),