Do not truncate crash messages in short test summary on CI (#9933)

Closes #9920

changelog/9920.improvement.rst

@@ -0,0 +1 @@
+Display full crash messages in ``short test summary info``, when runng in a CI environment.

src/_pytest/terminal.py

@@ -37,6 +37,7 @@ from _pytest._code import ExceptionInfo
 from _pytest._code.code import ExceptionRepr
 from _pytest._io import TerminalWriter
 from _pytest._io.wcwidth import wcswidth
+from _pytest.assertion.util import running_on_ci
 from _pytest.compat import final
 from _pytest.config import _PluggyPlugin
 from _pytest.config import Config
@@ -1315,8 +1316,11 @@ def _get_line_with_reprcrash_message(
     except AttributeError:
         pass
     else:
-        available_width = tw.fullwidth - line_width
-        msg = _format_trimmed(" - {}", msg, available_width)
+        if not running_on_ci():
+            available_width = tw.fullwidth - line_width
+            msg = _format_trimmed(" - {}", msg, available_width)
+        else:
+            msg = f" - {msg}"
         if msg is not None:
             line += msg
 

testing/test_terminal.py

@@ -1139,7 +1139,21 @@ class TestTerminalFunctional:
         assert result.stdout.lines.count(expected) == 1
 
 
-def test_fail_extra_reporting(pytester: Pytester, monkeypatch) -> None:
+@pytest.mark.parametrize(
+    ("use_ci", "expected_message"),
+    (
+        (True, f"- AssertionError: {'this_failed'*100}"),
+        (False, "- AssertionError: this_failedt..."),
+    ),
+    ids=("on CI", "not on CI"),
+)
+def test_fail_extra_reporting(
+    pytester: Pytester, monkeypatch, use_ci: bool, expected_message: str
+) -> None:
+    if use_ci:
+        monkeypatch.setenv("CI", "true")
+    else:
+        monkeypatch.delenv("CI", raising=False)
     monkeypatch.setenv("COLUMNS", "80")
     pytester.makepyfile("def test_this(): assert 0, 'this_failed' * 100")
     result = pytester.runpytest("-rN")
@@ -1148,7 +1162,7 @@ def test_fail_extra_reporting(pytester: Pytester, monkeypatch) -> None:
     result.stdout.fnmatch_lines(
         [
             "*test summary*",
-            "FAILED test_fail_extra_reporting.py::test_this - AssertionError: this_failedt...",
+            f"FAILED test_fail_extra_reporting.py::test_this {expected_message}",
         ]
     )