Add str() support to LineMatcher (#8050)

changelog/1265.improvement.rst

@@ -0,0 +1 @@
+Added an ``__str__`` implementation to the :class:`~pytest.pytester.LineMatcher` class which is returned from ``pytester.run_pytest().stdout`` and similar. It returns the entire output, like the existing ``str()`` method.

doc/en/reference.rst

@@ -527,6 +527,7 @@ To use it, include in your topmost ``conftest.py`` file:
 
 .. autoclass:: LineMatcher()
     :members:
+    :special-members: __str__
 
 .. autoclass:: HookRecorder()
     :members:

src/_pytest/pytester.py

@@ -512,7 +512,7 @@ class RunResult:
         self.stdout = LineMatcher(outlines)
         """:class:`LineMatcher` of stdout.
 
-        Use e.g. :func:`stdout.str() <LineMatcher.str()>` to reconstruct stdout, or the commonly used
+        Use e.g. :func:`str(stdout) <LineMatcher.__str__()>` to reconstruct stdout, or the commonly used
         :func:`stdout.fnmatch_lines() <LineMatcher.fnmatch_lines()>` method.
         """
         self.stderr = LineMatcher(errlines)
@@ -1707,6 +1707,14 @@ class LineMatcher:
         self.lines = lines
         self._log_output: List[str] = []
 
+    def __str__(self) -> str:
+        """Return the entire original text.
+
+        .. versionadded:: 6.2
+            You can use :meth:`str` in older versions.
+        """
+        return "\n".join(self.lines)
+
     def _getlines(self, lines2: Union[str, Sequence[str], Source]) -> Sequence[str]:
         if isinstance(lines2, str):
             lines2 = Source(lines2)
@@ -1908,4 +1916,4 @@ class LineMatcher:
 
     def str(self) -> str:
         """Return the entire original text."""
-        return "\n".join(self.lines)
+        return str(self)

testing/test_pytester.py

@@ -610,6 +610,11 @@ def test_linematcher_no_matching_after_match() -> None:
     assert str(e.value).splitlines() == ["fnmatch: '*'", "   with: '1'"]
 
 
+def test_linematcher_string_api() -> None:
+    lm = LineMatcher(["foo", "bar"])
+    assert str(lm) == "foo\nbar"
+
+
 def test_pytester_addopts_before_testdir(request, monkeypatch) -> None:
     orig = os.environ.get("PYTEST_ADDOPTS", None)
     monkeypatch.setenv("PYTEST_ADDOPTS", "--orig-unused")