Fix IndexError for positional-only default arguments

pycg/processing/preprocessor.py

@@ -50,13 +50,14 @@ def __init__(
 
     def _get_fun_defaults(self, node):
         defaults = {}
-        start = len(node.args.args) - len(node.args.defaults)
+        pos_args = node.args.posonlyargs + node.args.args
+        start = len(pos_args) - len(node.args.defaults)
         for cnt, d in enumerate(node.args.defaults, start=start):
             if not d:
                 continue
 
             self.visit(d)
-            defaults[node.args.args[cnt].arg] = self.decode_node(d)
+            defaults[pos_args[cnt].arg] = self.decode_node(d)
 
         start = len(node.args.kwonlyargs) - len(node.args.kw_defaults)
         for cnt, d in enumerate(node.args.kw_defaults, start=start):

pycg/tests/preprocessor_test.py

@@ -0,0 +1,69 @@
+#
+# Copyright (c) 2020 Vitalis Salis.
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+#
+import ast
+import os
+import tempfile
+
+from base import TestBase
+
+from pycg.machinery.classes import ClassManager
+from pycg.machinery.definitions import DefinitionManager
+from pycg.machinery.imports import ImportManager
+from pycg.machinery.modules import ModuleManager
+from pycg.machinery.scopes import ScopeManager
+from pycg.processing.preprocessor import PreProcessor
+
+
+class PreprocessorTest(TestBase):
+    def _make_preprocessor(self, code):
+        with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+            f.write(code)
+            fname = f.name
+
+        im = ImportManager()
+        sm = ScopeManager()
+        dm = DefinitionManager()
+        cm = ClassManager()
+        mm = ModuleManager()
+        pp = PreProcessor(fname, "mod", im, sm, dm, cm, mm, modules_analyzed=set())
+        return pp, fname
+
+    def test_get_fun_defaults_posonlyargs(self):
+        code = "def eye(n_rows, n_cols=None, /): pass\n"
+        pp, fname = self._make_preprocessor(code)
+        try:
+            node = ast.parse(code).body[0]
+            defaults = pp._get_fun_defaults(node)
+            self.assertIn("n_cols", defaults)
+            self.assertEqual(defaults["n_cols"], [None])
+        finally:
+            os.unlink(fname)
+
+    def test_get_fun_defaults_positional_or_keyword(self):
+        code = "def f(a, b=1): pass\n"
+        pp, fname = self._make_preprocessor(code)
+        try:
+            node = ast.parse(code).body[0]
+            defaults = pp._get_fun_defaults(node)
+            self.assertIn("b", defaults)
+            self.assertEqual(defaults["b"], [1])
+        finally:
+            os.unlink(fname)