ENG-7619: make console errors go to stderr (#5789)

* ENG-7619: make console errors go to stderr

* check err not out

Author: adhami3310

reflex/utils/console.py

@@ -22,6 +22,7 @@
 
 # Console for pretty printing.
 _console = Console()
+_console_stderr = Console(stderr=True)
 
 # The current log level.
 _LOG_LEVEL = LogLevel.INFO
@@ -96,6 +97,21 @@ def print(msg: str, *, dedupe: bool = False, **kwargs):
     _console.print(msg, **kwargs)
 
 
+def _print_stderr(msg: str, *, dedupe: bool = False, **kwargs):
+    """Print a message to stderr.
+
+    Args:
+        msg: The message to print.
+        dedupe: If True, suppress multiple console logs of print message.
+        kwargs: Keyword arguments to pass to the print function.
+    """
+    if dedupe:
+        if msg in _EMITTED_PRINTS:
+            return
+        _EMITTED_PRINTS.add(msg)
+    _console_stderr.print(msg, **kwargs)
+
+
 @once
 def log_file_console():
     """Create a console that logs to a file.
@@ -342,7 +358,7 @@ def error(msg: str, *, dedupe: bool = False, **kwargs):
             if msg in _EMITTED_ERRORS:
                 return
             _EMITTED_ERRORS.add(msg)
-        print(f"[red]{msg}[/red]", **kwargs)
+        _print_stderr(f"[red]{msg}[/red]", **kwargs)
     if should_use_log_file_console():
         print_to_log_file(f"[red]{msg}[/red]", **kwargs)
 

reflex/vars/base.py

@@ -2345,7 +2345,7 @@ def __get__(self, instance: BaseState | None, owner: type):
     def _check_deprecated_return_type(self, instance: BaseState, value: Any) -> None:
         if not _isinstance(value, self._var_type, nested=1, treat_var_as_type=False):
             console.error(
-                f"Computed var '{type(instance).__name__}.{self._js_expr}' must return"
+                f"Computed var '{type(instance).__name__}.{self._name}' must return"
                 f" a value of type '{escape(str(self._var_type))}', got '{value!s}' of type {type(value)}."
             )
 
@@ -2395,7 +2395,7 @@ def _deps(
         except Exception as e:
             console.warn(
                 "Failed to automatically determine dependencies for computed var "
-                f"{objclass.__name__}.{self._js_expr}: {e}. "
+                f"{objclass.__name__}.{self._name}: {e}. "
                 "Provide static_deps and set auto_deps=False to suppress this warning."
             )
             return d

tests/integration/test_exception_handlers.py

@@ -114,7 +114,7 @@ def driver(test_app: AppHarness) -> Generator[WebDriver, None, None]:
 
 def test_frontend_exception_handler_during_runtime(
     driver: WebDriver,
-    capsys,
+    capsys: pytest.CaptureFixture[str],
 ):
     """Test calling frontend exception handler during runtime.
 
@@ -136,13 +136,13 @@ def test_frontend_exception_handler_during_runtime(
     time.sleep(2)
 
     captured_default_handler_output = capsys.readouterr()
-    assert "induce_frontend_error" in captured_default_handler_output.out
-    assert "ReferenceError" in captured_default_handler_output.out
+    assert "induce_frontend_error" in captured_default_handler_output.err
+    assert "ReferenceError" in captured_default_handler_output.err
 
 
 def test_backend_exception_handler_during_runtime(
     driver: WebDriver,
-    capsys,
+    capsys: pytest.CaptureFixture[str],
 ):
     """Test calling backend exception handler during runtime.
 
@@ -164,14 +164,14 @@ def test_backend_exception_handler_during_runtime(
     time.sleep(2)
 
     captured_default_handler_output = capsys.readouterr()
-    assert "divide_by_number" in captured_default_handler_output.out
-    assert "ZeroDivisionError" in captured_default_handler_output.out
+    assert "divide_by_number" in captured_default_handler_output.err
+    assert "ZeroDivisionError" in captured_default_handler_output.err
 
 
 def test_frontend_exception_handler_with_react(
     test_app: AppHarness,
     driver: WebDriver,
-    capsys,
+    capsys: pytest.CaptureFixture[str],
 ):
     """Test calling frontend exception handler during runtime.
 
@@ -194,9 +194,9 @@ def test_frontend_exception_handler_with_react(
 
     captured_default_handler_output = capsys.readouterr()
     if isinstance(test_app, AppHarnessProd):
-        assert "Error: Minified React error #31" in captured_default_handler_output.out
+        assert "Error: Minified React error #31" in captured_default_handler_output.err
     else:
         assert (
             "Error: Objects are not valid as a React child (found: object with keys \n{invalid})"
-            in captured_default_handler_output.out
+            in captured_default_handler_output.err
         )

tests/units/test_state.py

@@ -1625,7 +1625,7 @@ def reset(self):
 
 
 @pytest.mark.asyncio
-async def test_state_with_invalid_yield(capsys, mock_app):
+async def test_state_with_invalid_yield(capsys: pytest.CaptureFixture[str], mock_app):
     """Test that an error is thrown when a state yields an invalid value.
 
     Args:
@@ -1664,7 +1664,7 @@ def invalid_handler(self):
             token="",
         )
     captured = capsys.readouterr()
-    assert "must only return/yield: None, Events or other EventHandlers" in captured.out
+    assert "must only return/yield: None, Events or other EventHandlers" in captured.err
 
 
 @pytest_asyncio.fixture(