fix: emit warning when TOML is invalid in a style file (closes #68)

Makefile

@@ -49,13 +49,13 @@ sphinx:
 	$(MAKE)
 
 # $(O) is meant as a shortcut for $(SPHINXOPTS).
-.cache/make/sphinx: docs *.rst *.md
+.cache/make/sphinx: src/* docs *.rst *.md
 	-rm -rf docs/source
-	sphinx-apidoc --force --module-first --separate --implicit-namespaces --output-dir docs/source src/nitpick/
+	sphinx-apidoc --force --module-first --separate --implicit-namespaces --output-dir docs/source src/
 	@$(SPHINXBUILD) "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
 	touch .cache/make/sphinx
 
-.cache/make/run: .github/* .travis/* docs/* src/nitpick/* styles/* tests/* nitpick-style.toml
+.cache/make/run: .github/* .travis/* docs/* src/* styles/* tests/* nitpick-style.toml
 	pre-commit run --all-files
 	flake8
 	touch .cache/make/run
@@ -64,6 +64,6 @@ pytest:
 	-rm .cache/make/pytest
 	$(MAKE)
 
-.cache/make/pytest: src/nitpick/* styles/* tests/*
+.cache/make/pytest: src/* styles/* tests/*
 	pytest
 	touch .cache/make/pytest

src/nitpick/config.py

@@ -19,6 +19,7 @@
     TOOL_NITPICK,
     TOOL_NITPICK_JMEX,
 )
+from nitpick.exceptions import StyleError
 from nitpick.files.pyproject_toml import PyProjectTomlFile
 from nitpick.files.setup_cfg import SetupCfgFile
 from nitpick.formats import TomlFormat
@@ -164,7 +165,11 @@ def merge_styles(self) -> YieldFlake8Error:
 
         configured_styles = self.tool_nitpick_dict.get("style", "")  # type: StrOrList
         style = Style(self)
-        style.find_initial_styles(configured_styles)
+        try:
+            style.find_initial_styles(configured_styles)
+        except StyleError as err:
+            yield self.style_error(err.style_file_name.name, "Invalid TOML:", err.args[0])
+
         self.style_dict = style.merge_toml_dict()
 
         from nitpick.plugin import NitpickChecker

src/nitpick/exceptions.py

@@ -0,0 +1,10 @@
+"""Nitpick exceptions."""
+from pathlib import Path
+
+
+class StyleError(Exception):
+    """An error in a style file."""
+
+    def __init__(self, style_file_name: Path, *args: object) -> None:
+        self.style_file_name = style_file_name
+        super().__init__(*args)

src/nitpick/style.py

@@ -6,6 +6,7 @@
 
 import requests
 from slugify import slugify
+from toml import TomlDecodeError
 
 from nitpick.constants import (
     DEFAULT_NITPICK_STYLE_URL,
@@ -14,6 +15,7 @@
     NITPICK_STYLES_INCLUDE_JMEX,
     TOML_EXTENSION,
 )
+from nitpick.exceptions import StyleError
 from nitpick.files.pyproject_toml import PyProjectTomlFile
 from nitpick.formats import TomlFormat
 from nitpick.generic import MergeDict, climb_directory_tree, is_url, search_dict
@@ -60,7 +62,10 @@ def include_multiple_styles(self, chosen_styles: StrOrList) -> None:
                 continue
 
             toml = TomlFormat(path=style_path)
-            self._all_styles.add(toml.as_data)
+            try:
+                self._all_styles.add(toml.as_data)
+            except TomlDecodeError as err:
+                raise StyleError(style_path, "{}: {}".format(err.__class__.__name__, err)) from err
 
             sub_styles = search_dict(NITPICK_STYLES_INCLUDE_JMEX, toml.as_data, [])  # type: StrOrList
             if sub_styles:

tests/test_style.py

@@ -499,3 +499,19 @@ def test_invalid_tool_nitpick_on_pyproject_toml(request):
             + " Invalid data in [tool.nitpick]:\x1b[92m\n{}\x1b[0m".format(error_message),
             1,
         )
+
+
+def test_invalid_toml(request):
+    """Invalid TOML should emit a NIP warning, not raise TomlDecodeError."""
+    ProjectMock(request).style(
+        """
+        ["setup.cfg".flake8]
+        ignore = D100,D104,D202,E203,W503
+        """
+    ).lint().assert_errors_contain(
+        """
+        NIP001 File nitpick-style.toml has an incorrect style. Invalid TOML:\x1b[92m
+        TomlDecodeError: This float doesn't have a leading digit (line 2 column 1 char 21)\x1b[0m
+        """,
+        1,
+    )