Prevent Markdown reporter crash when max_length is None

lib/urlwatch/reporters.py

@@ -824,12 +824,25 @@ def submit(self, max_length=None):
             details = None
 
         trimmed_msg = "*Parts of the report were omitted due to message length.*\n"
-        max_length -= len(trimmed_msg)
+        summary_raw = summary
+        details_raw = details
+        footer_raw = footer
 
         trimmed, summary, details, footer = MarkdownReporter._render(
-            max_length, summary, details, footer
+            max_length, summary_raw, details_raw, footer_raw
         )
 
+        trimmed_marker = trimmed_msg
+        if max_length is not None and trimmed:
+            if len(trimmed_marker) > max_length:
+                trimmed_marker = "[...]\n"
+                if len(trimmed_marker) > max_length:
+                    trimmed_marker = ""
+            reserved_length = max_length - len(trimmed_marker) if trimmed_marker else max_length
+            trimmed, summary, details, footer = MarkdownReporter._render(
+                reserved_length, summary_raw, details_raw, footer_raw
+            )
+
         if summary:
             yield from summary
             yield ''
@@ -840,8 +853,8 @@ def submit(self, max_length=None):
                 yield body
                 yield ''
 
-        if trimmed:
-            yield trimmed_msg
+        if trimmed and trimmed_marker:
+            yield trimmed_marker
 
         if summary and show_footer:
             yield from footer

lib/urlwatch/tests/test_reporters.py

@@ -0,0 +1,124 @@
+import datetime
+
+from urlwatch.reporters import MarkdownReporter
+
+
+class _DummyJob:
+    def pretty_name(self):
+        return "dummy"
+
+    def get_location(self):
+        return "dummy"
+
+
+class _DummyJobState:
+    def __init__(self, verb="changed", old_data="old", new_data="new", diff="diff"):
+        self.job = _DummyJob()
+        self.verb = verb
+        self.old_data = old_data
+        self.new_data = new_data
+        self._diff = diff
+        self.traceback = "traceback"
+
+    def get_diff(self):
+        return self._diff
+
+
+class _DummyReport:
+    def __init__(self):
+        self.config = {
+            "report": {
+                "markdown": {
+                    "details": True,
+                    "footer": True,
+                    "minimal": False,
+                    "separate": False,
+                }
+            }
+        }
+
+    def get_filtered_job_states(self, job_states):
+        return job_states
+
+
+def test_markdown_submit_without_max_length_does_not_crash():
+    report = _DummyReport()
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [], datetime.timedelta())
+
+    output = list(reporter.submit(max_length=None))
+
+    assert output == []
+
+
+def test_markdown_submit_with_trimming_returns_notice():
+    report = _DummyReport()
+    job_state = _DummyJobState(diff="line1\nline2\nline3")
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    output = list(reporter.submit(max_length=80))
+
+    assert any("Parts of the report were omitted" in line for line in output)
+
+
+def test_markdown_submit_uses_fallback_marker_when_notice_too_long():
+    report = _DummyReport()
+    report.config["report"]["markdown"]["footer"] = False
+    job_state = _DummyJobState(diff="line1\nline2\nline3")
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    output = list(reporter.submit(max_length=30))
+
+    assert any("[...]" in line for line in output)
+    assert not any("Parts of the report were omitted" in line for line in output)
+
+
+def test_markdown_submit_with_tiny_max_length_does_not_exceed_limit():
+    report = _DummyReport()
+    job_state = _DummyJobState(diff="line1\nline2\nline3")
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    max_length = 5
+    output = list(reporter.submit(max_length=max_length))
+
+    total_length = sum(len(line) + 1 for line in output) - 1 if output else 0
+    assert total_length <= max_length
+
+
+def test_markdown_submit_with_zero_max_length_is_empty():
+    report = _DummyReport()
+    job_state = _DummyJobState(diff="line1\nline2\nline3")
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    output = list(reporter.submit(max_length=0))
+
+    assert output == []
+
+
+def test_markdown_submit_trims_with_footer():
+    report = _DummyReport()
+    job_state = _DummyJobState(diff=("line\n" * 200))
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    max_length = None
+    output = []
+    for length in range(80, 200):
+        output = list(reporter.submit(max_length=length))
+        if (any("urlwatch" in line for line in output)
+                and any("Parts of the report were omitted" in line for line in output)):
+            max_length = length
+            break
+
+    assert max_length is not None
+
+
+def test_markdown_submit_does_not_trim_when_length_exact():
+    report = _DummyReport()
+    report.config["report"]["markdown"]["details"] = False
+    report.config["report"]["markdown"]["footer"] = False
+    job_state = _DummyJobState(old_data=None)
+    reporter = MarkdownReporter(report, report.config["report"]["markdown"], [job_state], datetime.timedelta())
+
+    max_length = len("1. CHANGED: dummy")
+    output = list(reporter.submit(max_length=max_length))
+
+    assert not any("Parts of the report were omitted" in line for line in output)