Add option to disable short summary truncation

changelog/10264.feature.rst

@@ -0,0 +1 @@
+Added the :option:`--no-truncate-summary` option to show complete first lines of messages in the short test summary.

doc/en/reference/reference.rst

@@ -3179,6 +3179,11 @@ Output and Reporting
 
     Force condensed summary output regardless of verbosity level.
 
+.. option:: --no-truncate-summary
+
+    Do not truncate messages in the short test summary, regardless of terminal width.
+    Only the first line of each message is displayed.
+
 .. option:: -l, --showlocals
 
     Show locals in tracebacks (disabled by default).

src/_pytest/terminal.py

@@ -178,6 +178,12 @@ def pytest_addoption(parser: Parser) -> None:
         default=False,
         help="Force condensed summary output regardless of verbosity level.",
     )
+    group.addoption(
+        "--no-truncate-summary",
+        action="store_true",
+        default=False,
+        help="Do not truncate messages in the short test summary.",
+    )
     group._addoption(  # private to use reserved lower-case short option
         "-q",
         "--quiet",
@@ -1596,9 +1602,12 @@ def _get_line_with_reprcrash_message(
     except AttributeError:
         pass
     else:
-        if (
-            running_on_ci() or config.option.verbose >= 2
-        ) and not config.option.force_short_summary:
+        if config.option.force_short_summary:
+            available_width = tw.fullwidth - line_width
+            msg = _format_trimmed(" - {}", msg, available_width)
+        elif config.option.no_truncate_summary:
+            msg = " - " + msg.partition("\n")[0]
+        elif running_on_ci() or config.option.verbose >= 2:
             msg = f" - {msg}"
         else:
             available_width = tw.fullwidth - line_width

testing/test_terminal.py

@@ -2738,7 +2738,11 @@ def __init__(self, **kwargs):
 
     class config:
         def __init__(self):
-            self.option = Namespace(verbose=0)
+            self.option = Namespace(
+                verbose=0,
+                force_short_summary=False,
+                no_truncate_summary=False,
+            )
 
     class rep:
         def _get_verbose_word_with_markup(self, *args):
@@ -2886,6 +2890,54 @@ def test():
     )
 
 
+@pytest.mark.parametrize(
+    ("args", "running_on_ci", "truncated"),
+    [
+        ([], False, True),
+        (["--no-truncate-summary"], False, False),
+        (["--no-truncate-summary"], True, False),
+        (["-vv", "--force-short-summary"], False, True),
+        (["--no-truncate-summary", "-vv", "--force-short-summary"], False, True),
+    ],
+)
+def test_no_truncate_summary(
+    monkeypatch: MonkeyPatch,
+    pytester: Pytester,
+    args: list[str],
+    running_on_ci: bool,
+    truncated: bool,
+) -> None:
+    monkeypatch.setattr(_pytest.terminal, "running_on_ci", lambda: running_on_ci)
+    monkeypatch.setenv("COLUMNS", "80")
+    pytester.makepyfile(
+        test_summary="""
+        import pytest
+
+        def test_fail():
+            pytest.fail("A" * 100 + "\\nSECOND_LINE")
+        """
+    )
+
+    result = pytester.runpytest(*args)
+    assert result.ret == 1
+
+    summary_index = next(
+        i
+        for i, line in enumerate(result.stdout.lines)
+        if "short test summary info" in line
+    )
+    summary_line = next(
+        line
+        for line in result.stdout.lines[summary_index + 1 :]
+        if line.startswith("FAILED test_summary.py::test_fail ")
+    )
+    assert "SECOND_LINE" not in summary_line
+    if truncated:
+        assert summary_line.endswith("...")
+    else:
+        assert "A" * 100 in summary_line
+
+
 @pytest.mark.parametrize(
     "seconds, expected",
     [