Typecheck xmllint with ament_mypy

ament_xmllint/ament_xmllint/main.py

@@ -20,15 +20,21 @@
 import subprocess
 import sys
 import time
+from typing import Any
+from typing import Literal
+from typing_extensions import TypeAlias
 from xml.etree import ElementTree
 from xml.sax import make_parser
 from xml.sax import SAXParseException
+from xml.sax.xmlreader import AttributesImpl
 from xml.sax.handler import ContentHandler
 from xml.sax.saxutils import escape
 from xml.sax.saxutils import quoteattr
 
+ReturnCode: TypeAlias = Literal[0, 1, "Could not find 'xmllint' executable"]
 
-def main(argv=sys.argv[1:]):
+
+def main(argv: list[str] = sys.argv[1:]) -> ReturnCode:
     default_extensions = ['xml']
 
     parser = argparse.ArgumentParser(
@@ -72,16 +78,16 @@ def main(argv=sys.argv[1:]):
     if not xmllint_bin:
         return "Could not find 'xmllint' executable"
 
-    report = []
+    report: list[tuple[str, Any]] = []
 
     # invoke xmllint on all files
     for filename in files:
         # parse file to extract desired validation information
-        parser = make_parser()
+        xml_parser = make_parser()
         handler = CustomHandler()
-        parser.setContentHandler(handler)
+        xml_parser.setContentHandler(handler)
         try:
-            parser.parse(filename)
+            xml_parser.parse(filename)
         except SAXParseException:
             pass
 
@@ -131,7 +137,7 @@ def main(argv=sys.argv[1:]):
     error_count = sum(1 if r[1] else 0 for r in report)
     if not error_count:
         print('No problems found')
-        rc = 0
+        rc: ReturnCode = 0
     else:
         print('%d files are invalid' % error_count, file=sys.stderr)
         rc = 1
@@ -158,8 +164,9 @@ def main(argv=sys.argv[1:]):
     return rc
 
 
-def get_files(paths, extensions, excludes=[]):
-    files = []
+def get_files(paths: list[str], extensions: list[str],
+              excludes: list[str] = []) -> list[str]:
+    files: list[str] = []
     for path in paths:
         if os.path.isdir(path):
             for dirpath, dirnames, filenames in os.walk(path):
@@ -187,31 +194,31 @@ def get_files(paths, extensions, excludes=[]):
 
 class CustomHandler(ContentHandler):
 
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__()
-        self.xml_model_attributes = []
-        self.root_attributes = {}
+        self.xml_model_attributes: list[dict[str, str]] = []
+        self.root_attributes: dict[str, str] = {}
         self._first_node = False
 
-    def processingInstruction(self, target, data):
+    def processingInstruction(self, target: str, data: str) -> None:
         if target != 'xml-model':
             return
 
         root = ElementTree.fromstring('<data ' + data + '/>')
         self.xml_model_attributes.append(root.attrib)
 
-    def startDocument(self):
+    def startDocument(self) -> None:
         self._first_node = True
 
-    def startElement(self, name, attrs):
+    def startElement(self, name: str, attrs: AttributesImpl) -> None:
         if not self._first_node:
             return
         self._first_node = False
         for attr_name in attrs.getNames():
             self.root_attributes[attr_name] = attrs.getValue(attr_name)
 
 
-def get_xunit_content(report, testname, elapsed):
+def get_xunit_content(report: list[tuple[str, Any]], testname: str, elapsed: float) -> str:
     test_count = len(report)
     error_count = len([r for r in report if r[1]])
     data = {

ament_xmllint/ament_xmllint/pytest_marker.py

@@ -13,7 +13,9 @@
 # limitations under the License.
 
 
-def pytest_configure(config):
+from _pytest.config import Config
+
+def pytest_configure(config: Config) -> None:
     config.addinivalue_line(
         'markers',
         'xmllint: marks tests checking XML files being well formed and valid')

ament_xmllint/package.xml

@@ -20,10 +20,12 @@
 
   <exec_depend>ament_lint</exec_depend>
   <exec_depend>libxml2-utils</exec_depend>
+  <exec_depend>python3-typing-extensions</exec_depend>
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>
   <test_depend>ament_pep257</test_depend>
+  <test_depend>ament_mypy</test_depend>
   <test_depend>python3-pytest</test_depend>
 
   <export>

ament_xmllint/test/test_copyright.py

@@ -18,6 +18,6 @@
 
 @pytest.mark.copyright
 @pytest.mark.linter
-def test_copyright():
+def test_copyright() -> None:
     rc = main(argv=[])
     assert rc == 0, 'Found errors'

ament_xmllint/test/test_flake8.py

@@ -18,7 +18,7 @@
 
 @pytest.mark.flake8
 @pytest.mark.linter
-def test_flake8():
+def test_flake8() -> None:
     rc, errors = main_with_errors(argv=[])
     assert rc == 0, \
         'Found %d code style errors / warnings:\n' % len(errors) + \

ament_xmllint/test/test_mypy.py

@@ -0,0 +1,21 @@
+# Copyright 2026 Open Source Robotics Foundation, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from ament_mypy.main import main
+
+
+def test_mypy() -> None:
+    rc = main(argv=[])
+    assert rc == 0, 'Found code style errors / warnings'

ament_xmllint/test/test_pep257.py

@@ -18,6 +18,6 @@
 
 @pytest.mark.linter
 @pytest.mark.pep257
-def test_pep257():
+def test_pep257() -> None:
     rc = main(argv=[])
     assert rc == 0, 'Found docblock style errors'

ament_xmllint/test/test_xmllint.py

@@ -24,6 +24,6 @@
 
 @pytest.mark.linter
 @pytest.mark.xmllint
-def test_xmllint():
+def test_xmllint() -> None:
     rc = main(argv=[])
     assert rc == 0, 'Found errors'