nightly_revert_checker: add stale HEAD notifications

This notifies teams when this tool doesn't observe their LLVM revision
moving for a while. The intent isn't to put pressure on LLVM upgrade
rotations; more to catch bugs in this checker earlier rather than later.

BUG=b:319635292
TEST=Unittests

Change-Id: I211b8803f483a96952f5d573bdb083ac723d3ca4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/5200618
Commit-Queue: George Burgess <gbiv@chromium.org>
Reviewed-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
Tested-by: George Burgess <gbiv@chromium.org>

1 files changed, 110 insertions, 0 deletions

diff --git a/llvm_tools/nightly_revert_checker_test.py b/llvm_tools/nightly_revert_checker_test.py
index 7e95766d..722ad125 100755
--- a/llvm_tools/nightly_revert_checker_test.py
+++ b/llvm_tools/nightly_revert_checker_test.py
@@ -184,6 +184,7 @@ class Test(unittest.TestCase):
         nightly_revert_checker.do_cherrypick(
             chroot_path="/path/to/chroot",
             llvm_dir="/path/to/llvm",
+            repository="repository_name",
             interesting_shas=[("12345abcdef", "fedcba54321")],
             state=nightly_revert_checker.State(),
             reviewers=["meow@chromium.org"],
@@ -207,6 +208,7 @@ class Test(unittest.TestCase):
         nightly_revert_checker.do_cherrypick(
             chroot_path="/path/to/chroot",
             llvm_dir="/path/to/llvm",
+            repository="repository_name",
             interesting_shas=[("12345abcdef", "fedcba54321")],
             state=nightly_revert_checker.State(),
             reviewers=["meow@chromium.org"],
@@ -230,6 +232,114 @@ class Test(unittest.TestCase):
             ),
         )
 
+    @mock.patch("time.time")
+    def test_emailing_about_stale_heads_skips_in_simple_cases(self, time_time):
+        now = 1_000_000_000
+        time_time.return_value = now
+
+        def assert_no_email(state: nightly_revert_checker.State):
+            self.assertFalse(
+                nightly_revert_checker.maybe_email_about_stale_heads(
+                    state,
+                    repository_name="foo",
+                    recipients=nightly_revert_checker._EmailRecipients(
+                        well_known=[], direct=[]
+                    ),
+                    prettify_sha=lambda *args: self.fail(
+                        "SHAs shouldn't be prettified"
+                    ),
+                    is_dry_run=True,
+                )
+            )
+
+        assert_no_email(nightly_revert_checker.State())
+        assert_no_email(
+            nightly_revert_checker.State(
+                heads={
+                    "foo": nightly_revert_checker.HeadInfo(
+                        last_sha="",
+                        first_seen_timestamp=0,
+                        next_notification_timestamp=now + 1,
+                    ),
+                    "bar": nightly_revert_checker.HeadInfo(
+                        last_sha="",
+                        first_seen_timestamp=0,
+                        next_notification_timestamp=now * 2,
+                    ),
+                }
+            )
+        )
+
+    def test_state_autoupgrades_from_json_properly(self):
+        state = nightly_revert_checker.State.from_json({"abc123": ["def456"]})
+        self.assertEqual(state.seen_reverts, {"abc123": ["def456"]})
+        self.assertEqual(state.heads, {})
+
+    def test_state_round_trips_through_json(self):
+        state = nightly_revert_checker.State(
+            seen_reverts={"abc123": ["def456"]},
+            heads={
+                "head_name": nightly_revert_checker.HeadInfo(
+                    last_sha="abc",
+                    first_seen_timestamp=123,
+                    next_notification_timestamp=456,
+                ),
+            },
+        )
+        self.assertEqual(
+            state, nightly_revert_checker.State.from_json(state.to_json())
+        )
+
+    @mock.patch("time.time")
+    @mock.patch("nightly_revert_checker._send_revert_email")
+    def test_emailing_about_stale_with_one_report(
+        self, send_revert_email, time_time
+    ):
+        def prettify_sha(sha: str) -> str:
+            return f"pretty({sha})"
+
+        now = 1_000_000_000
+        two_days_ago = now - 2 * nightly_revert_checker.ONE_DAY_SECS
+        time_time.return_value = now
+        recipients = nightly_revert_checker._EmailRecipients(
+            well_known=[], direct=[]
+        )
+        self.assertTrue(
+            nightly_revert_checker.maybe_email_about_stale_heads(
+                nightly_revert_checker.State(
+                    heads={
+                        "foo": nightly_revert_checker.HeadInfo(
+                            last_sha="<foo sha>",
+                            first_seen_timestamp=two_days_ago,
+                            next_notification_timestamp=now - 1,
+                        ),
+                        "bar": nightly_revert_checker.HeadInfo(
+                            last_sha="",
+                            first_seen_timestamp=0,
+                            next_notification_timestamp=now + 1,
+                        ),
+                    }
+                ),
+                repository_name="repo",
+                recipients=recipients,
+                prettify_sha=prettify_sha,
+                is_dry_run=False,
+            )
+        )
+        send_revert_email.assert_called_once()
+        recipients, email = send_revert_email.call_args[0]
+
+        self.assertEqual(
+            tiny_render.render_text_pieces(email.body),
+            "Hi! This is a friendly notification that the current upstream "
+            "LLVM SHA is being tracked by the LLVM revert checker:\n"
+            "  - foo at pretty(<foo sha>), which was last updated ~2 days "
+            "ago.\n"
+            "If that's still correct, great! If it looks wrong, the revert "
+            "checker's SHA autodetection may need an update. Please file a "
+            "bug at go/crostc-bug if an update is needed. Thanks!",
+        )
+
 
 if __name__ == "__main__":
     unittest.main()