Fix crash on unparseable datetime range in khal new -i

CHANGELOG.rst

@@ -7,6 +7,13 @@ Package maintainers and users who have to manually update their installation
 may want to subscribe to `GitHub's tag feed
 <https://github.com/geier/khal/tags.atom>`_.
 
+0.14.3
+======
+unreleased
+* FIX ``khal new -i`` crashed and discarded the whole event (summary, etc.)
+  when given an unparseable datetime range, it now reports the problem and
+  asks again
+
 0.14.2
 ======
 unreleased

khal/controllers.py

@@ -378,9 +378,15 @@ def new_interactive(
             end_string = info["dtend"].strftime(conf["locale"]["datetimeformat"])
             range_string = start_string + " " + end_string
         daterange = prompt("datetime range", default=range_string)
-        start, end, allday = parse_datetime.guessrangefstr(
-            daterange, conf["locale"], adjust_reasonably=True
-        )
+        try:
+            start, end, allday = parse_datetime.guessrangefstr(
+                daterange, conf["locale"], adjust_reasonably=True
+            )
+        except DateTimeParseError as error:
+            # Let the user retry just the datetime range instead of losing
+            # the whole event.
+            echo(error)
+            continue
         info["dtstart"] = start
         info["dtend"] = end
         info["allday"] = allday

khal/parse_datetime.py

@@ -414,11 +414,14 @@ def guessrangefstr(
         except (ValueError, DateTimeParseError):
             pass
 
+    example = dt.datetime(2013, 12, 21, 21, 45).strftime(locale["datetimeformat"])
     raise DateTimeParseError(
-        f'Could not parse "{daterange}".\nPlease check your configuration or '
-        "run `khal printformats` to see if this does match your configured "
-        "[long](date|time|datetime)format.\nIf you suspect a bug, please "
-        "file an issue at https://github.com/pimutils/khal/issues/ "
+        f'Could not parse "{daterange}" as a daterange.\n'
+        f'Try formatting dates like this: "{example}".\n'
+        "Please check your configuration or run `khal printformats` to see "
+        "if this does match your configured [long](date|time|datetime)format."
+        "\nIf you suspect a bug, please file an issue at "
+        "https://github.com/pimutils/khal/issues/ "
     )
 
 

tests/cli_test.py

@@ -1144,6 +1144,54 @@ def test_issue_1056(runner):
     assert result.exit_code == 0
 
 
+@freeze_time("2015-6-1 8:00")
+def test_issue_789(runner):
+    """an unparseable datetime range in `khal new -i` shouldn't discard the
+    whole event and crash, it should report the problem and let the user
+    retry just the datetime range
+    """
+    runner = runner(print_new="path")
+
+    result = runner.invoke(
+        main_khal,
+        ["new", "-i"],
+        "Coffee w/Somebody\n"
+        "tuesday 13:30 - 14:30\n"  # unparseable, from the original report
+        "13:00 17:00\n"  # retry with a range that does parse
+        "\n"
+        "None\n"
+        "n\n",
+    )
+    assert "Could not parse" in result.output
+    assert "event saved" in result.output
+    assert not result.exception
+    assert result.exit_code == 0
+
+
+@freeze_time("2015-6-1 8:00")
+def test_issue_789_multiple_invalid_attempts(runner):
+    """the retry from #789 should work for as many bad attempts as the user
+    makes, not just a single one
+    """
+    runner = runner(print_new="path")
+
+    result = runner.invoke(
+        main_khal,
+        ["new", "-i"],
+        "Coffee w/Somebody\n"
+        "tuesday 13:30 - 14:30\n"  # unparseable
+        "still not valid input\n"  # still unparseable
+        "13:00 17:00\n"  # finally parses
+        "\n"
+        "None\n"
+        "n\n",
+    )
+    assert result.output.count("Could not parse") == 2
+    assert "event saved" in result.output
+    assert not result.exception
+    assert result.exit_code == 0
+
+
 def test_list_now(runner, tmpdir):
     # reproduce #693
     runner = runner()

tests/parse_datetime_test.py

@@ -1,4 +1,5 @@
 import datetime as dt
+import re
 from collections import OrderedDict
 
 import pytest
@@ -353,6 +354,29 @@ def test_invalid(self):
         with pytest.raises(DateTimeParseError):
             guessrangefstr("xxx yyy zzz", locale=LOCALE_BERLIN)
 
+    def test_invalid_error_includes_example(self):
+        """the error for an unparseable daterange should recommend a
+        formatted example, not just say that the input was rejected
+        """
+        with pytest.raises(DateTimeParseError, match="Try formatting dates like this"):
+            guessrangefstr("xxx yyy zzz", locale=LOCALE_BERLIN)
+
+    def test_invalid_error_example_matches_locale(self):
+        """the recommended example should reflect the caller's own
+        configured datetimeformat, not a fixed string.
+        """
+        # same reference datetime `khal printformats` uses to demonstrate formats
+        reference = dt.datetime(2013, 12, 21, 21, 45)
+
+        berlin_example = reference.strftime(LOCALE_BERLIN["datetimeformat"])
+        with pytest.raises(DateTimeParseError, match=re.escape(berlin_example)):
+            guessrangefstr("xxx yyy zzz", locale=LOCALE_BERLIN)
+
+        new_york_example = reference.strftime(LOCALE_NEW_YORK["datetimeformat"])
+        assert berlin_example != new_york_example
+        with pytest.raises(DateTimeParseError, match=re.escape(new_york_example)):
+            guessrangefstr("xxx yyy zzz", locale=LOCALE_NEW_YORK)
+
     @freeze_time("2016-12-30 17:53")
     def test_short_format_contains_year(self):
         """if the non long versions of date(time)format contained a year, the