Validate pyproject.toml configuration more stringently

Co-authored-by: Amethyst Reese <amy@n7.gg>

ufmt/config.py

@@ -1,13 +1,15 @@
 # Copyright 2022 Amethyst Reese
 # Licensed under the MIT license
-
+import logging
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Any, Dict, List, Optional
+from typing import List, Optional, Sequence
 
 import tomlkit
 from trailrunner import project_root
 
+LOG = logging.getLogger(__name__)
+
 
 @dataclass
 class UfmtConfig:
@@ -22,13 +24,26 @@ def ufmt_config(path: Optional[Path] = None) -> UfmtConfig:
     config_path = root / "pyproject.toml"
     if config_path.is_file():
         pyproject = tomlkit.loads(config_path.read_text())
-        config: Dict[str, Any] = {}
-
-        if "tool" in pyproject and "ufmt" in pyproject["tool"]:  # type: ignore
-            config.update(pyproject["tool"]["ufmt"])  # type: ignore
-
-        config["project_root"] = root
-        config["pyproject_path"] = config_path
-        return UfmtConfig(**config)
+        config = pyproject.get("tool", {}).get("ufmt", {})
+        if not isinstance(config, dict):
+            LOG.warning("%s: tool.ufmt is not a mapping, ignoring", config_path)
+            config = {}
+
+        config_excludes = config.pop("excludes", [])
+        if isinstance(config_excludes, Sequence) and not isinstance(
+            config_excludes, str
+        ):
+            excludes = [str(x) for x in config_excludes]
+        else:
+            raise ValueError(f"{config_path}: excludes must be a list of strings")
+
+        if config:
+            LOG.warning("%s: unknown values ignored: %r", config_path, sorted(config))
+
+        return UfmtConfig(
+            project_root=root,
+            pyproject_path=config_path,
+            excludes=excludes,
+        )
 
     return UfmtConfig()

ufmt/tests/config.py

@@ -5,6 +5,7 @@
 from tempfile import TemporaryDirectory
 from textwrap import dedent
 from unittest import TestCase
+from unittest.mock import ANY, patch
 
 from trailrunner.tests.core import cd
 
@@ -93,3 +94,119 @@ def test_ufmt_config(self):
                     ),
                     config,
                 )
+
+    @patch("ufmt.config.LOG")
+    def test_invalid_config(self, log_mock):
+        with self.subTest("string"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool]
+                    ufmt = "hello"
+                    """
+                )
+            )
+            expected = UfmtConfig(project_root=self.td, pyproject_path=self.pyproject)
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+
+            log_mock.warning.assert_called_once()
+            log_mock.reset_mock()
+
+        with self.subTest("array"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [[tool.ufmt]]
+                    excludes = ["fixtures/"]
+                    """
+                )
+            )
+            expected = UfmtConfig(project_root=self.td, pyproject_path=self.pyproject)
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+
+            log_mock.warning.assert_called_once()
+            log_mock.reset_mock()
+
+        with self.subTest("extra"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool.ufmt]
+                    unknown_element = true
+                    hello_world = "my name is"
+                    """
+                )
+            )
+            expected = UfmtConfig(project_root=self.td, pyproject_path=self.pyproject)
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+
+            log_mock.warning.assert_called_with(
+                ANY, self.pyproject, ["hello_world", "unknown_element"]
+            )
+            log_mock.reset_mock()
+
+    @patch("ufmt.config.LOG")
+    def test_config_excludes(self, log_mock):
+        with self.subTest("missing"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool.ufmt]
+                    """
+                )
+            )
+            expected = UfmtConfig(project_root=self.td, pyproject_path=self.pyproject)
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+            log_mock.assert_not_called()
+
+        with self.subTest("empty"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool.ufmt]
+                    excludes = []
+                    """
+                )
+            )
+            expected = UfmtConfig(
+                project_root=self.td, pyproject_path=self.pyproject, excludes=[]
+            )
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+            log_mock.assert_not_called()
+
+        with self.subTest("list"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool.ufmt]
+                    excludes = ["fixtures/"]
+                    """
+                )
+            )
+            expected = UfmtConfig(
+                project_root=self.td,
+                pyproject_path=self.pyproject,
+                excludes=["fixtures/"],
+            )
+            result = ufmt_config(self.td / "fake.py")
+            self.assertEqual(expected, result)
+            log_mock.assert_not_called()
+
+        with self.subTest("string"):
+            self.pyproject.write_text(
+                dedent(
+                    """
+                    [tool.ufmt]
+                    excludes = "fixtures/"
+                    """
+                )
+            )
+            with self.assertRaisesRegex(
+                ValueError, "excludes must be a list of strings"
+            ):
+                ufmt_config(self.td / "fake.py")