Rework how a typed parameter is handled (#311)

This change utilizes the visitor pattern to process nodes of type
typed_parameter and typed_default_parameter instead of manually checking
children of the function def. This works because typed parameters are
only within function defs.

This commit also adds test cases to ensure this is working.

This change also protects against the traceback found when encountering
an unexpected *arg as a function parameter.

Fixes #310

Signed-off-by: Eric Brown <[email protected]>

precli/parsers/python.py

@@ -50,41 +50,35 @@ def visit_class_definition(self, nodes: list[Node]):
     def visit_function_definition(self, nodes: list[Node]):
         func_id = self.child_by_type(self.context["node"], "identifier")
         func = func_id.text.decode()
-
         self.current_symtab = SymbolTable(func, parent=self.current_symtab)
+        self.visit(nodes)
+        self.current_symtab = self.current_symtab.parent()
 
-        func_parameters = self.child_by_type(
-            self.context["node"], "parameters"
-        )
-        func_args = func_parameters.named_children
-
-        for func_arg in func_args:
-            # typed_parameter or identifier
-            if func_arg.type == "typed_parameter":
-                param_id = self.child_by_type(func_arg, "identifier")
-                param_type = self.child_by_type(func_arg, "type")
-
-                if param_type.named_children[0].type in (
-                    "attribute",
-                    "identifier",
-                    "string",
-                    "integer",
-                    "float",
-                    "true",
-                    "false",
-                    "none",
-                ):
-                    param_name = param_id.text.decode()
-                    param_type = self.literal_value(
-                        param_type.named_children[0],
-                        default=param_type.named_children[0],
-                    )
-                    self.current_symtab.put(
-                        param_name, "identifier", param_type
-                    )
+    def visit_typed_default_parameter(self, nodes: list[Node]):
+        self.visit_typed_parameter(nodes)
+
+    def visit_typed_parameter(self, nodes: list[Node]):
+        param_id = self.child_by_type(self.context["node"], "identifier")
+        param_type = self.child_by_type(self.context["node"], "type")
+
+        if param_id is not None and param_type.named_children[0].type in (
+            "attribute",
+            "identifier",
+            "string",
+            "integer",
+            "float",
+            "true",
+            "false",
+            "none",
+        ):
+            param_name = param_id.text.decode()
+            param_type = self.literal_value(
+                param_type.named_children[0],
+                default=param_type.named_children[0],
+            )
+            self.current_symtab.put(param_name, "identifier", param_type)
 
         self.visit(nodes)
-        self.current_symtab = self.current_symtab.parent()
 
     def visit_named_expression(self, nodes: list[Node]):
         if len(nodes) > 1 and nodes[1].text.decode() == ":=":

tests/unit/rules/python/stdlib/examples/ssl_context_set_ecdh_curve_typed_default_param.py

@@ -0,0 +1,14 @@
+# level: WARNING
+# start_line: 10
+# end_line: 10
+# start_column: 27
+# end_column: 39
+import ssl
+
+
+def set_curve(context: ssl.SSLContext = None) -> None:
+    context.set_ecdh_curve("prime192v1")
+
+
+context = ssl.SSLContext()
+set_curve(context)

tests/unit/rules/python/stdlib/examples/ssl_context_set_ecdh_curve_typed_param.py

@@ -0,0 +1,14 @@
+# level: WARNING
+# start_line: 10
+# end_line: 10
+# start_column: 27
+# end_column: 39
+import ssl
+
+
+def set_curve(context: ssl.SSLContext) -> None:
+    context.set_ecdh_curve("prime192v1")
+
+
+context = ssl.SSLContext()
+set_curve(context)

tests/unit/rules/python/stdlib/test_ssl_context_weak_key.py

@@ -49,6 +49,8 @@ def test_rule_meta(self):
             "ssl_context_set_ecdh_curve_secp256r1.py",
             "ssl_context_set_ecdh_curve_sect163k1.py",
             "ssl_context_set_ecdh_curve_sect571k1.py",
+            "ssl_context_set_ecdh_curve_typed_default_param.py",
+            "ssl_context_set_ecdh_curve_typed_param.py",
             "ssl_context_set_ecdh_curve_unverified_context.py",
         ]
     )