[PR #13462/cba5c4a9 backport][8.4.x] fix: support TerminalReporter.isatty being called

changelog/13461.bugfix.rst

@@ -0,0 +1,3 @@
+Corrected ``_pytest.terminal.TerminalReporter.isatty`` to support
+being called as a method. Before it was just a boolean which could
+break correct code when using ``-o log_cli=true``).

src/_pytest/compat.py

@@ -300,3 +300,23 @@ def get_user_id() -> int | None:
 # This also work for Enums (if you use `is` to compare) and Literals.
 def assert_never(value: NoReturn) -> NoReturn:
     assert False, f"Unhandled value: {value} ({type(value).__name__})"
+
+
+class CallableBool:
+    """
+    A bool-like object that can also be called, returning its true/false value.
+
+    Used for backwards compatibility in cases where something was supposed to be a method
+    but was implemented as a simple attribute by mistake (see `TerminalReporter.isatty`).
+
+    Do not use in new code.
+    """
+
+    def __init__(self, value: bool) -> None:
+        self._value = value
+
+    def __bool__(self) -> bool:
+        return self._value
+
+    def __call__(self) -> bool:
+        return self._value

src/_pytest/terminal.py

@@ -31,6 +31,7 @@
 
 import pluggy
 
+from _pytest import compat
 from _pytest import nodes
 from _pytest import timing
 from _pytest._code import ExceptionInfo
@@ -387,7 +388,9 @@ def __init__(self, config: Config, file: TextIO | None = None) -> None:
         self.reportchars = getreportopt(config)
         self.foldskipped = config.option.fold_skipped
         self.hasmarkup = self._tw.hasmarkup
-        self.isatty = file.isatty()
+        # isatty should be a method but was wrongly implemented as a boolean.
+        # We use CallableBool here to support both.
+        self.isatty = compat.CallableBool(file.isatty())
         self._progress_nodeids_reported: set[str] = set()
         self._timing_nodeids_reported: set[str] = set()
         self._show_progress_info = self._determine_show_progress_info()
@@ -766,7 +769,7 @@ def _width_of_current_line(self) -> int:
         return self._tw.width_of_current_line
 
     def pytest_collection(self) -> None:
-        if self.isatty:
+        if self.isatty():
             if self.config.option.verbose >= 0:
                 self.write("collecting ... ", flush=True, bold=True)
         elif self.config.option.verbose >= 1:
@@ -779,7 +782,7 @@ def pytest_collectreport(self, report: CollectReport) -> None:
             self._add_stats("skipped", [report])
         items = [x for x in report.result if isinstance(x, Item)]
         self._numcollected += len(items)
-        if self.isatty:
+        if self.isatty():
             self.report_collect()
 
     def report_collect(self, final: bool = False) -> None:
@@ -811,7 +814,7 @@ def report_collect(self, final: bool = False) -> None:
             line += f" / {skipped} skipped"
         if self._numcollected > selected:
             line += f" / {selected} selected"
-        if self.isatty:
+        if self.isatty():
             self.rewrite(line, bold=True, erase=True)
             if final:
                 self.write("\n")

testing/test_terminal.py

@@ -442,6 +442,16 @@ def test_long_xfail():
             ]
         )
 
+    @pytest.mark.parametrize("isatty", [True, False])
+    def test_isatty(self, pytester: Pytester, monkeypatch, isatty: bool) -> None:
+        config = pytester.parseconfig()
+        f = StringIO()
+        monkeypatch.setattr(f, "isatty", lambda: isatty)
+        tr = TerminalReporter(config, f)
+        assert tr.isatty() == isatty
+        # It was incorrectly implemented as a boolean so we still support using it as one.
+        assert bool(tr.isatty) == isatty
+
 
 class TestCollectonly:
     def test_collectonly_basic(self, pytester: Pytester) -> None: