Create a framework of functional tests for configuration files

Also migrate three standard unittest to the new framework for testing.

9 files changed, 202 insertions, 47 deletions

diff --git a/pylint/testutils/configuration_test.py b/pylint/testutils/configuration_test.py
new file mode 100644
index 000000000..00d828b08
--- /dev/null
+++ b/pylint/testutils/configuration_test.py
@@ -0,0 +1,85 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+
+"""Utility function for configuration testing."""
+import copy
+import json
+import unittest
+from pathlib import Path
+from typing import Any, Dict, Tuple, Union
+
+from pylint.lint import Run
+
+USER_SPECIFIC = str(Path(__file__).parent.parent.parent)
+
+
+def get_expected_or_default(pyproject_toml_path: str, suffix: str, default: Any) -> str:
+    def get_path_according_to_suffix() -> Path:
+        path = Path(pyproject_toml_path)
+        return path.parent / f"{path.stem}.{suffix}"
+
+    expected = default
+    expected_result_path = get_path_according_to_suffix()
+    if expected_result_path.exists():
+        with open(expected_result_path, encoding="utf8") as f:
+            expected = f.read()
+    return expected
+
+
+EXPECTED_CONF_APPEND_KEY = "functional_append"
+EXPECTED_CONF_REMOVE_KEY = "functional_remove"
+EXPECTED_CONF_SPECIAL_KEYS = [EXPECTED_CONF_APPEND_KEY, EXPECTED_CONF_REMOVE_KEY]
+
+
+def get_expected_configuration(
+    configuration_path: str, default_configuration: Dict[str, Any]
+) -> Dict[str, Any]:
+    """Get the expected parsed configuration of a configuration functional test"""
+    result = copy.deepcopy(default_configuration)
+    config_as_json = get_expected_or_default(
+        configuration_path, suffix="result.json", default="{}"
+    )
+    to_override = json.loads(config_as_json)
+    for key, value in to_override.items():
+        if key not in EXPECTED_CONF_SPECIAL_KEYS:
+            result[key] = value
+    if EXPECTED_CONF_APPEND_KEY in to_override:
+        for key, value in to_override[EXPECTED_CONF_APPEND_KEY].items():
+            result[key] += value
+    if EXPECTED_CONF_REMOVE_KEY in to_override:
+        for key, value in to_override[EXPECTED_CONF_REMOVE_KEY].items():
+            result[key] -= value
+    return result
+
+
+def get_expected_output(configuration_path: str) -> Tuple[int, str]:
+    """Get the expected output of a functional test."""
+
+    def get_relative_path(path: str) -> str:
+        """Get the relative path we want without user specific information"""
+        return path.replace(USER_SPECIFIC, "")[1:]
+
+    output = get_expected_or_default(configuration_path, suffix="out", default="")
+    exit_code = 2 if output else 0
+    return exit_code, output.format(
+        abspath=configuration_path, relpath=get_relative_path(configuration_path)
+    )
+
+
+def run_using_a_configuration_file(
+    configuration_path: Union[Path, str], file_to_lint: str = __file__
+) -> Tuple[unittest.mock.Mock, unittest.mock.Mock, Run]:
+    """Simulate a run with a configuration without really launching the checks."""
+    configuration_path = str(configuration_path)
+    args = ["--rcfile", configuration_path, file_to_lint]
+    # If we used `pytest.raises(SystemExit)`, the `runner` variable
+    # would not be accessible outside the `with` block.
+    with unittest.mock.patch("sys.exit") as mocked_exit:
+        # Do not actually run checks, that could be slow. Do not mock
+        # `Pylinter.check`: it calls `Pylinter.initialize` which is
+        # needed to properly set up messages inclusion/exclusion
+        # in `_msg_states`, used by `is_message_enabled`.
+        check = "pylint.lint.pylinter.check_parallel"
+        with unittest.mock.patch(check) as mocked_check_parallel:
+            runner = Run(args)
+    return mocked_exit, mocked_check_parallel, runner
diff --git a/tests/config/functional/ini/pylintrc_with_message_control.ini b/tests/config/functional/ini/pylintrc_with_message_control.ini
new file mode 100644
index 000000000..95d99036f
--- /dev/null
+++ b/tests/config/functional/ini/pylintrc_with_message_control.ini
@@ -0,0 +1,5 @@
+# Check that we can read the "regular" INI .pylintrc file
+[messages control]
+disable = logging-not-lazy,logging-format-interpolation
+jobs = 10
+reports = yes
diff --git a/tests/config/functional/ini/pylintrc_with_message_control.result.json b/tests/config/functional/ini/pylintrc_with_message_control.result.json
new file mode 100644
index 000000000..21938c319
--- /dev/null
+++ b/tests/config/functional/ini/pylintrc_with_message_control.result.json
@@ -0,0 +1,7 @@
+{
+  "functional_append": {
+    "disable": [["logging-not-lazy"], ["logging-format-interpolation"]]
+  },
+  "jobs": 10,
+  "reports": true
+}
diff --git a/tests/config/functional/setup_cfg/setup_cfg_with_message_control.cfg b/tests/config/functional/setup_cfg/setup_cfg_with_message_control.cfg
new file mode 100644
index 000000000..d5e4c564c
--- /dev/null
+++ b/tests/config/functional/setup_cfg/setup_cfg_with_message_control.cfg
@@ -0,0 +1,5 @@
+# setup.cfg is an INI file where section names are prefixed with "pylint."
+[pylint.messages control]
+disable = logging-not-lazy,logging-format-interpolation
+jobs = 10
+reports = yes
diff --git a/tests/config/functional/setup_cfg/setup_cfg_with_message_control.result.json b/tests/config/functional/setup_cfg/setup_cfg_with_message_control.result.json
new file mode 100644
index 000000000..21938c319
--- /dev/null
+++ b/tests/config/functional/setup_cfg/setup_cfg_with_message_control.result.json
@@ -0,0 +1,7 @@
+{
+  "functional_append": {
+    "disable": [["logging-not-lazy"], ["logging-format-interpolation"]]
+  },
+  "jobs": 10,
+  "reports": true
+}
diff --git a/tests/config/functional/toml/toml_with_message_control.result.json b/tests/config/functional/toml/toml_with_message_control.result.json
new file mode 100644
index 000000000..21938c319
--- /dev/null
+++ b/tests/config/functional/toml/toml_with_message_control.result.json
@@ -0,0 +1,7 @@
+{
+  "functional_append": {
+    "disable": [["logging-not-lazy"], ["logging-format-interpolation"]]
+  },
+  "jobs": 10,
+  "reports": true
+}
diff --git a/tests/config/functional/toml/toml_with_message_control.toml b/tests/config/functional/toml/toml_with_message_control.toml
new file mode 100644
index 000000000..0e58d8918
--- /dev/null
+++ b/tests/config/functional/toml/toml_with_message_control.toml
@@ -0,0 +1,7 @@
+# Check that we can read a TOML file where lists and integers are
+# expressed as strings.
+
+[tool.pylint."messages control"]
+disable = "logging-not-lazy,logging-format-interpolation"
+jobs = "10"
+reports = "yes"
diff --git a/tests/config/test_config.py b/tests/config/test_config.py
index 8ce5d9b42..723d4636e 100644
--- a/tests/config/test_config.py
+++ b/tests/config/test_config.py
@@ -46,53 +46,6 @@ def check_configuration_file_reader(
     assert bool(runner.linter.config.reports) == expected_reports_truthey
 
 
-def test_can_read_ini(tmp_path: Path) -> None:
-    # Check that we can read the "regular" INI .pylintrc file
-    config_file = tmp_path / ".pylintrc"
-    config_file.write_text(
-        """
-[messages control]
-disable = logging-not-lazy,logging-format-interpolation
-jobs = 10
-reports = yes
-"""
-    )
-    run = get_runner_from_config_file(config_file)
-    check_configuration_file_reader(run)
-
-
-def test_can_read_setup_cfg(tmp_path: Path) -> None:
-    # Check that we can read a setup.cfg (which is an INI file where
-    # section names are prefixed with "pylint."
-    config_file = tmp_path / "setup.cfg"
-    config_file.write_text(
-        """
-[pylint.messages control]
-disable = logging-not-lazy,logging-format-interpolation
-jobs = 10
-reports = yes
-"""
-    )
-    run = get_runner_from_config_file(config_file)
-    check_configuration_file_reader(run)
-
-
-def test_can_read_toml(tmp_path: Path) -> None:
-    # Check that we can read a TOML file where lists and integers are
-    # expressed as strings.
-    config_file = tmp_path / "pyproject.toml"
-    config_file.write_text(
-        """
-[tool.pylint."messages control"]
-disable = "logging-not-lazy,logging-format-interpolation"
-jobs = "10"
-reports = "yes"
-"""
-    )
-    run = get_runner_from_config_file(config_file)
-    check_configuration_file_reader(run)
-
-
 def test_can_read_toml_rich_types(tmp_path: Path) -> None:
     # Check that we can read a TOML file where lists, integers and
     # booleans are expressed as such (and not as strings), using TOML
diff --git a/tests/config/test_functional_config_loading.py b/tests/config/test_functional_config_loading.py
new file mode 100644
index 000000000..5d3696c2f
--- /dev/null
+++ b/tests/config/test_functional_config_loading.py
@@ -0,0 +1,79 @@
+# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
+# For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
+
+"""
+This launch the configuration functional tests. This permit to test configuration
+files by providing a file with the appropriate extension in the ``tests/config/functional``
+directory.
+
+Let's say you have a regression_list_crash.toml file to test. Then if there is an error in the conf,
+add ``regression_list_crash.out`` alongside your file with the expected output of pylint in it. Use
+``{relpath}`` and ``{abspath}`` for the path of the file. The exit code will have to be 2 (error)
+if this file exists.
+
+You must also define a ``regression_list_crash.result.json`` if you want to check the parsed configuration.
+This file will be loaded as a dict and will override the default value of the default pylint
+configuration. If you need to append or remove a value use the special key ``"functional_append"``
+and ``"functional_remove":``. Check the existing code for example.
+"""
+
+# pylint: disable=redefined-outer-name
+
+from pathlib import Path
+from typing import Any, Dict
+
+import pytest
+from _pytest.capture import CaptureFixture
+
+from pylint.testutils.configuration_test import (
+    get_expected_configuration,
+    get_expected_output,
+    run_using_a_configuration_file,
+)
+
+HERE = Path(__file__).parent
+FUNCTIONAL_DIR = HERE / "functional"
+# We use string then recast to path so we can use -k in pytest otherwise
+# we get 'configuration_path0' as a test name. Relative to the functional
+# directory because otherwise the string is very lengthy
+CONFIGURATION_PATHS = [
+    str(path.relative_to(FUNCTIONAL_DIR))
+    for ext in ("toml", "ini", "cfg")
+    for path in FUNCTIONAL_DIR.rglob(f"*.{ext}")
+]
+FILE_TO_LINT = str(HERE / "file_to_lint.py")
+
+
+@pytest.fixture()
+def default_configuration(tmp_path: Path) -> Dict[str, Any]:
+    empty_pylintrc = tmp_path / "pylintrc"
+    empty_pylintrc.write_text("")
+    mock_exit, _, runner = run_using_a_configuration_file(
+        str(empty_pylintrc), FILE_TO_LINT
+    )
+    mock_exit.assert_called_once_with(0)
+    return runner.linter.config.__dict__
+
+
+@pytest.mark.parametrize("configuration_path", CONFIGURATION_PATHS)
+def test_functional_config_loading(
+    configuration_path: str,
+    default_configuration: Dict[str, Any],
+    capsys: CaptureFixture,
+):
+    """Functional tests for configurations."""
+    configuration_path = str(FUNCTIONAL_DIR / configuration_path)
+    msg = f"Wrong result with configuration {configuration_path}"
+    expected_code, expected_output = get_expected_output(configuration_path)
+    expected_loaded_configuration = get_expected_configuration(
+        configuration_path, default_configuration
+    )
+    mock_exit, _, runner = run_using_a_configuration_file(
+        configuration_path, FILE_TO_LINT
+    )
+    mock_exit.assert_called_once_with(expected_code)
+    out, err = capsys.readouterr()
+    # rstrip() applied so we can have a final newline in the expected test file
+    assert expected_output.rstrip() == out.rstrip(), msg
+    assert expected_loaded_configuration == runner.linter.config.__dict__
+    assert not err, msg