Add a support of --append-config

.github/workflows/test.yml

@@ -17,5 +17,4 @@ jobs:
       - name: Install
         run: python -m pip install .
       - name: Test
-        working-directory: .github/workflows/test
-        run: pflake8
+        run: python -m unittest discover -v -s test

pflake8/__init__.py

@@ -32,8 +32,11 @@ def _read(self, fp, filename):
             )
 
             for section, config in section_to_copy.items():
-                self.add_section(section)
-                self._sections[section] = self._dict(config)
+                try:
+                    self.add_section(section)
+                except (configparser.DuplicateSectionError):
+                    pass
+                self._sections.setdefault(section, self._dict()).update(self._dict(config))
         else:
             super(ConfigParserTomlMixin, self)._read(fp, filename)
 

pyproject.toml

@@ -26,6 +26,9 @@ name = "pflake8"
 
 [tool.black]
 skip-string-normalization = 1
+force-exclude = [
+    "test/data/dummy.py",
+]
 
 [tool.isort]
 profile = "black"
@@ -35,4 +38,4 @@ multi_line_output = 3
 max-line-length = 88
 extend-ignore = ["E203"]
 max-complexity = 10
-exclude = "venv"
+exclude = ["venv", "test/data/"]

test/data/dummy.py

@@ -0,0 +1,5 @@
+d = {"a" : 1}  # E203
+
+
+def a_long_name_function_definition(x="this is a test for", y="--max-line-length setting."):  # E501
+    pass

test/data/pyproject.toml

@@ -0,0 +1,2 @@
+[tool.flake8]
+extend-ignore = ["E203"]

test/data/setup.cfg

@@ -0,0 +1,2 @@
+[flake8]
+max-line-length = 120

test/data/setup_custom.cfg

@@ -0,0 +1,2 @@
+[flake8]
+extend-ignore = E203

test/test_append_config.py

@@ -0,0 +1,33 @@
+import sys
+import unittest
+import pflake8
+
+
+class TestAppendConfig(unittest.TestCase):
+    def test_append_config_toml(self):
+        sys.argv = [
+            "pflake8",
+            "--config",
+            "./test/data/setup.cfg",
+            "--append-config",
+            "./test/data/pyproject.toml",
+            "./test/data/dummy.py",
+        ]
+
+        pflake8.main()  # OK if this raises no exception.
+
+    def test_append_config_normal(self):
+        sys.argv = [
+            "pflake8",
+            "--config",
+            "./test/data/setup.cfg",
+            "--append-config",
+            "./test/data/setup_custom.cfg",
+            "./test/data/dummy.py",
+        ]
+
+        pflake8.main()  # OK if this raises no exception.
+
+
+if __name__ == '__main__':
+    unittest.main()