fix: correctly print multi-line errors (#270)

* fix: correctly print multi-line errors

The bug manifested in a situation like this:

- A long progress() message is printed, say "AAAAAAAA";
- An error is emitter, and the result of str(error) is a multi-line string
  where the first line is shorter than the previously-emitted progress()
  message. Example: "BBBB\nCCCC";
- The newline in the error message is not correctly handled by the printer,
  meaning that after "BBBB" is written to the terminal the remainder of the
  line is not cleared. So the end result looks like:
  > BBBBAAAA
  > CCCC

The "proper" fix for this would mean a big rework on the printer to properly
support multi-line messages; for now, fix only the error case by "manually"
splitting the error message and printing each line individually.

Fixes #263
---------

Co-authored-by: Matt Culler <[email protected]>

craft_cli/messages.py

@@ -710,7 +710,7 @@ def ended_ok(self) -> None:
         """Finish the messaging system gracefully."""
         self._stop()
 
-    def _report_error(self, error: errors.CraftError) -> None:
+    def _report_error(self, error: errors.CraftError) -> None:  # noqa: PLR0912 (too many branches)
         """Report the different message lines from a CraftError."""
         if self._mode in (EmitterMode.QUIET, EmitterMode.BRIEF, EmitterMode.VERBOSE):
             use_timestamp = False
@@ -719,8 +719,10 @@ def _report_error(self, error: errors.CraftError) -> None:
             use_timestamp = True
             full_stream = sys.stderr
 
-        # the initial message
-        self._printer.show(sys.stderr, str(error), use_timestamp=use_timestamp, end_line=True)
+        # The initial message. Print every line individually to correctly clear
+        # previous lines, if necessary.
+        for line in str(error).splitlines():
+            self._printer.show(sys.stderr, line, use_timestamp=use_timestamp, end_line=True)
 
         if isinstance(error, errors.CraftCommandError):
             stderr = error.stderr

examples.py

@@ -513,6 +513,15 @@ def example_30():
         time.sleep(0.001)
 
 
+def example_31():
+    """Multiline error message."""
+    emit.progress("Setting up computer for build...")
+    time.sleep(1)
+    emit.progress("A long progress message")
+    time.sleep(6)
+    raise CraftError("Error 1\nError 2")
+
+
 # -- end of test cases
 
 if len(sys.argv) < 2:

tests/integration/test_messages_integration.py

@@ -1010,6 +1010,23 @@ def test_error_unexpected_debugish(capsys, mode):
     assert_outputs(capsys, emit, expected_err=expected, expected_log=expected)
 
 
+@pytest.mark.parametrize("output_is_terminal", [True])
+def test_error_multiline_brief(capsys):
+    emit = Emitter()
+    emit.init(EmitterMode.BRIEF, "testapp", GREETING)
+    emit.progress("A very long message detailing the current task.")
+    error = CraftError("Error line 1.\nError line 2.", logpath_report=False)
+    emit.error(error)
+
+    expected = [
+        Line("A very long message detailing the current task.", permanent=False),
+        # The error message is split on two separate lines.
+        Line("Error line 1.", permanent=True),
+        Line("Error line 2.", permanent=True),
+    ]
+    assert_outputs(capsys, emit, expected_err=expected, expected_log=expected)
+
+
 @pytest.mark.parametrize(
     "mode",
     [