Skip the results email when no reports were parsed (#200)

The [smtp] (and Microsoft Graph) results email was sent unconditionally
whenever the transport was configured, so an empty run — an empty inbox,
or one where every message was invalid — still emailed a zip of
headers-only CSVs. The email step is now skipped with an INFO log when
the run produced no aggregate, failure, or SMTP TLS reports.

The regression test was verified to fail against the unfixed code
(send_email was called once with a headers-only zip). Six existing tests
that asserted on the email path with all-empty mocked results now feed a
real parsed sample aggregate report through the actual zip/CSV-building
code instead.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_cli.py

@@ -26,6 +26,21 @@ import parsedmarc
 import parsedmarc.cli
 import parsedmarc.elastic
 import parsedmarc.opensearch as opensearch_module
+from parsedmarc.types import AggregateReport
+
+SAMPLE_AGGREGATE_REPORT_PATH = (
+    "samples/aggregate/!example.com!1538204542!1538463818.xml"
+)
+
+
+def _sample_aggregate_reports() -> list[AggregateReport]:
+    """Parses a real sample aggregate report so tests that exercise the
+    real zip/CSV-building code path (email_results / email_results_via_msgraph)
+    have a fully valid AggregateReport rather than a hand-built partial
+    dict that would fail in parsed_aggregate_reports_to_csv_rows()."""
+    result = parsedmarc.parse_report_file(SAMPLE_AGGREGATE_REPORT_PATH, offline=True)
+    assert result["report_type"] == "aggregate"
+    return [cast(AggregateReport, result["report"])]
 
 
 class _BreakLoop(BaseException):
@@ -1892,7 +1907,7 @@ certificate_password = s3cret-cert-pass
         """[smtp] with only to/subject (no host) plus [msgraph] sends the
         summary via Microsoft Graph's sendMail."""
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -1928,7 +1943,7 @@ subject = DMARC Summary
         set, even with [msgraph] also configured — no fallback, no
         dual-send."""
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -2009,7 +2024,7 @@ to = admin@example.com
         """A Graph sendMail failure gets the same single-ERROR-line
         treatment as connection/fetch failures."""
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -2054,7 +2069,7 @@ subject = DMARC Summary
         Graph path, the configured attachment filename and message
         body must reach send_message()."""
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -3732,7 +3747,7 @@ class TestSmtpAttachmentAndMessageWiring(unittest.TestCase):
         email_results() rather than being silently dropped."""
         mock_imap_connection.return_value = object()
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -3777,7 +3792,7 @@ message = Custom body text
         than being called with no attachment/message context at all."""
         mock_imap_connection.return_value = object()
         mock_get_mailbox_reports.return_value = {
-            "aggregate_reports": [],
+            "aggregate_reports": _sample_aggregate_reports(),
             "failure_reports": [],
             "smtp_tls_reports": [],
         }
@@ -3807,6 +3822,101 @@ to = admin@example.com
         )
 
 
+class TestSkipsResultsEmailWhenNoReportsParsed(unittest.TestCase):
+    """#200: a run that parses no reports at all (e.g. an empty inbox,
+    or a mailbox where every message failed to parse) must not send a
+    results email with headers-only, data-free CSVs. The email step is
+    now skipped, with an INFO log line, whenever aggregate_reports,
+    failure_reports, and smtp_tls_reports are all empty."""
+
+    def _write_config(self, config_text):
+        with tempfile.NamedTemporaryFile("w", suffix=".ini", delete=False) as cfg:
+            cfg.write(config_text)
+            cfg_path = cfg.name
+        self.addCleanup(lambda: os.path.exists(cfg_path) and os.remove(cfg_path))
+        return cfg_path
+
+    def _run_main(self, cfg_path, *cli_args):
+        with patch.object(sys, "argv", ["parsedmarc", "-c", cfg_path, *cli_args]):
+            parsedmarc.cli._main()
+
+    @patch("parsedmarc.send_email")
+    @patch("parsedmarc.cli.get_dmarc_reports_from_mailbox")
+    @patch("parsedmarc.cli.IMAPConnection")
+    def testSkipsResultsEmailWhenNothingWasParsed(
+        self, mock_imap_connection, mock_get_mailbox_reports, mock_send_email
+    ):
+        """Regression test for #200: with an empty inbox (no aggregate,
+        failure, or SMTP TLS reports), the SMTP results email must not
+        be sent, and an INFO log line should explain why it was
+        skipped."""
+        mock_imap_connection.return_value = object()
+        mock_get_mailbox_reports.return_value = {
+            "aggregate_reports": [],
+            "failure_reports": [],
+            "smtp_tls_reports": [],
+        }
+        config_text = """[general]
+silent = true
+verbose = true
+
+[imap]
+host = imap.example.com
+user = test-user
+password = test-password
+
+[smtp]
+host = smtp.example.com
+user = smtp-user
+password = smtp-password
+from = dmarc@example.com
+to = admin@example.com
+"""
+        cfg_path = self._write_config(config_text)
+
+        with self.assertLogs("parsedmarc.log", level="INFO") as logs:
+            self._run_main(cfg_path)
+
+        mock_send_email.assert_not_called()
+        self.assertTrue(
+            any("skipping the results email" in line for line in logs.output)
+        )
+
+    @patch("parsedmarc.send_email")
+    def testSendsResultsEmailWithRealPayloadWhenReportsExist(self, mock_send_email):
+        """When at least one report is parsed, the results email is
+        still sent, and the attached zip's aggregate.csv contains actual
+        data rows (not just a header row)."""
+        config_text = """[general]
+silent = true
+offline = true
+
+[smtp]
+host = smtp.example.com
+user = smtp-user
+password = smtp-password
+from = dmarc@example.com
+to = admin@example.com
+"""
+        cfg_path = self._write_config(config_text)
+
+        with patch.object(
+            sys,
+            "argv",
+            ["parsedmarc", "-c", cfg_path, SAMPLE_AGGREGATE_REPORT_PATH],
+        ):
+            parsedmarc.cli._main()
+
+        mock_send_email.assert_called_once()
+        call_kwargs = mock_send_email.call_args.kwargs
+        attachments = call_kwargs["attachments"]
+        filename, zip_bytes = attachments[0]
+        with zipfile.ZipFile(io.BytesIO(zip_bytes)) as zf:
+            csv_text = zf.read("aggregate.csv").decode("utf-8")
+
+        self.assertGreater(len(csv_text.strip().splitlines()), 1)
+
+
 class TestParseConfigS3(unittest.TestCase):
     def test_s3_complete(self):
         from parsedmarc.cli import _parse_config