Add prototype plugin

flake8p/hook.py

@@ -3,12 +3,10 @@
 import flake8.main.cli
 import flake8.options.config
 import sys
-if sys.version_info >= (3, 11):
-    import tomllib as toml
-else:
-    import tomli as toml
 from pathlib import Path
 
+from flake8p.util import load_flake8_from_toml, find_and_load_toml_file, normalize_from_toml
+
 
 # Remember original Flake8 objects.
 flake8_RawConfigParser  = flake8.options.config.configparser.RawConfigParser
@@ -23,29 +21,23 @@ class RawConfigParser(flake8_RawConfigParser):
     def _read(self, stream, path):
         file = Path(path)
         if file.name == 'pyproject.toml':
-            with file.open('rb') as f:
-                settings = toml.load(f)
+            _, settings = load_flake8_from_toml(file)
             if not self.has_section('flake8'):
                 self.add_section('flake8')
-            for (key, value) in settings['tool']['flake8'].items():
-                if isinstance(value, (bool, int, float)):
-                    value = str(value)
+            settings = normalize_from_toml(settings)
+            for (key, value) in settings['flake8'].items():
                 self.set('flake8', key, value)
         else:
             super()._read(stream, path)
 
 
 def find_config_file(path):
     """Convinces Flake8 to prefer `pyproject.toml` over other config files."""
-    file = Path(path)/'pyproject.toml'
-    if file.exists():
-        with file.open('rb') as f:
-            settings = toml.load(f)
-        if 'tool' in settings and 'flake8' in settings['tool']:
-            return str(file)
+    config_path, config = find_and_load_toml_file(path)
+    if config_path and config:
+        return str(config_path)
     return flake8_find_config_file(path)
 
-
 # Monkey-patch Flake8 with our modified objects.
 flake8.options.config.configparser.RawConfigParser = RawConfigParser
 flake8.options.config._find_config_file = find_config_file

flake8p/plugin.py

@@ -0,0 +1,19 @@
+from typing import Any, Dict, List
+import configparser
+
+from flake8p.util import monkeypatch
+
+import flake8.options.config
+
+class FlakeConfigToml:
+    def __init__(self, tree):
+        pass
+
+    def __iter__(self):
+        raise StopIteration()
+
+    def run(self, *args) -> List[Any]:
+        return []
+
+    def add_options(self, *args):
+        monkeypatch()

flake8p/util.py

@@ -0,0 +1,80 @@
+from typing import Tuple, Any, Dict, List, Optional
+from pathlib import Path
+import configparser
+
+if sys.version_info >= (3, 11):
+    import tomllib as toml
+else:
+    import tomli as toml
+
+import flake8.options.config
+
+def _stat_key(p: Path) -> Tuple[int, int]:
+    st = p.stat()
+    return st.st_ino, st.st_dev
+
+def load_flake8_from_toml(filename: Path) -> Dict[str, Any]:
+    try:
+        with filename.open('rb') as f:
+            settings = toml.load(f)
+        if 'tool' in settings and 'flake8' in settings['tool']:
+            return {"flake8": settings["tool"]["flake8"]}
+        else:
+            return {}
+    except Exception:
+        return {}
+
+def normalize_from_toml(settings: Dict[str, Any]) -> Dict[str, Any]:
+    output = {}
+    for key, value in settings["flake8"].items():
+        if isinstance(value, (bool, int, float)):
+            value = str(value)
+        elif isinstance(value, list):
+            value = ",".join(str(x) for x in value)
+        output[key] = value
+    return {"flake8": output}
+
+def find_and_load_toml_file(_path: Optional[str]) -> Tuple[Optional[Path], Dict[str, Any]]:
+    if _path:
+        path = Path(_path).resolve()
+    else:
+        path = Path(".").resolve()
+    try:
+        # if the homedir isn't detected expanduser() raises RuntimeError
+        home_stat = _stat_key(Path("~").expanduser())
+    except RuntimeError:
+        home_stat = None
+
+    dir_stat = _stat_key(path)
+    while True:
+        cfg_path = path / "pyproject.toml"
+        if cfg_path.exists():
+            cfg = load_flake8_from_toml(cfg_path)
+            if cfg:
+                return cfg_path, cfg
+        new_path = path.parent
+        new_dir_stat = _stat_key(new_path)
+        if new_dir_stat == dir_stat or new_dir_stat == home_stat:
+            break
+        else:
+            path = new_path
+            dir_stat = new_dir_stat
+
+    # did not find any configuration file
+    return None, {}
+
+def monkeypatch():
+    flake8_parse_config = flake8.options.config.parse_config
+    flake8_option_manager = flake8.options.config.OptionManager
+
+    def parse_config(
+        option_manager: flake8_option_manager,
+        cfg: configparser.RawConfigParser,
+        cfg_dir: str,
+    ) -> Dict[str, Any]:
+        loaded_toml = find_and_load_toml_file()
+        normalized = normalize_from_toml(loaded_toml)
+        cfg.read_dict(normalized)
+        return flake8_parse_config(option_manager, cfg, cfg_dir)
+
+    flake8.options.config.parse_config = parse_config

pyproject.toml

@@ -26,6 +26,9 @@ dependencies = [
 [project.scripts]
 flake8p = 'flake8p:main'
 
+[project.entry-points."flake8.extensions"]
+CFG999 = "flake8p.plugin:FlakeConfigToml"
+
 [project.optional-dependencies]
 test = ['pyTest', 'pyTest-cov']