Merge pull request #1498 from rkm/fix-missing-config

return an error if the explicitly specified config is missing

src/flake8/options/config.py

@@ -8,6 +8,7 @@ from typing import List
 from typing import Optional
 from typing import Tuple
 
+from flake8 import exceptions
 from flake8.options.manager import OptionManager
 
 LOG = logging.getLogger(__name__)
@@ -60,7 +61,10 @@ def load_config(
 
     cfg = configparser.RawConfigParser()
     if config is not None:
-        cfg.read(config)
+        if not cfg.read(config):
+            raise exceptions.ExecutionError(
+                f"The specified config file does not exist: {config}"
+            )
         cfg_dir = os.path.dirname(config)
     else:
         cfg_dir = pwd

tests/integration/test_main.py

@@ -386,3 +386,21 @@ def test_early_keyboard_interrupt_does_not_crash(capsys):
     out, err = capsys.readouterr()
     assert out == "... stopped\n"
     assert err == ""
+
+
+def test_config_file_not_found(tmpdir, capsys):
+    """Ensure that an explicitly specified config file which is not found is an
+    error"""
+
+    expected = """\
+There was a critical error during execution of Flake8:
+The specified config file does not exist: missing.cfg
+"""
+
+    with tmpdir.as_cwd():
+        tmpdir.join("t.py").write("print('hello hello world')\n")
+        assert cli.main(["--config", "missing.cfg", "t.py"]) == 1
+
+    out, err = capsys.readouterr()
+    assert out == expected
+    assert err == ""

tests/unit/test_options_config.py

@@ -2,6 +2,7 @@ import configparser
 
 import pytest
 
+from flake8 import exceptions
 from flake8.main.options import register_default_options
 from flake8.options import config
 from flake8.options.manager import OptionManager
@@ -164,3 +165,8 @@ def test_parse_config_ignores_unknowns(tmp_path, opt_manager, caplog):
             'Option "wat" is not registered. Ignoring.',
         )
     ]
+
+
+def test_load_config_missing_file_raises_exception(capsys):
+    with pytest.raises(exceptions.ExecutionError):
+        config.load_config("foo.cfg", [])