T7042: drop use of inspect module in favor of ast for source analysis

This avoids importing the config mode script as a module, with requisite
dependencies, which may be inconvenient.

src/tests/test_configd_inspect.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2020-2024 VyOS maintainers and contributors
+# Copyright (C) 2020-2025 VyOS maintainers and contributors
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 or later as
@@ -12,93 +12,151 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-import os
-import re
+import ast
 import json
 
-import warnings
-import importlib.util
-from inspect import signature
-from inspect import getsource
-from functools import wraps
 from unittest import TestCase
 
 INC_FILE = 'data/configd-include.json'
 CONF_DIR = 'src/conf_mode'
 
-f_list = ['get_config', 'verify', 'generate', 'apply']
-
-def import_script(s):
-    path = os.path.join(CONF_DIR, s)
-    name = os.path.splitext(s)[0].replace('-', '_')
-    spec = importlib.util.spec_from_file_location(name, path)
-    module = importlib.util.module_from_spec(spec)
-    spec.loader.exec_module(module)
-    return module
-
-# importing conf_mode scripts imports jinja2 with deprecation warning
-def ignore_deprecation_warning(f):
-    @wraps(f)
-    def decorated_function(*args, **kwargs):
-        with warnings.catch_warnings():
-            warnings.simplefilter("ignore")
-            f(*args, **kwargs)
-    return decorated_function
+funcs = ['get_config', 'verify', 'generate', 'apply']
+
+
+class FunctionSig(ast.NodeVisitor):
+    def __init__(self):
+        self.func_sig_len = dict.fromkeys(funcs, None)
+        self.get_config_default_values = []
+
+    def visit_FunctionDef(self, node):
+        func_name = node.name
+        if func_name in funcs:
+            self.func_sig_len[func_name] = len(node.args.args)
+
+        if func_name == 'get_config':
+            for default in node.args.defaults:
+                if isinstance(default, ast.Constant):
+                    self.get_config_default_values.append(default.value)
+
+        self.generic_visit(node)
+
+    def get_sig_lengths(self):
+        return self.func_sig_len
+
+    def get_config_default(self):
+        return self.get_config_default_values[0]
+
+
+class LegacyCall(ast.NodeVisitor):
+    def __init__(self):
+        self.legacy_func_count = 0
+
+    def visit_Constant(self, node):
+        value = node.value
+        if isinstance(value, str):
+            if 'my_set' in value or 'my_delete' in value:
+                self.legacy_func_count += 1
+
+        self.generic_visit(node)
+
+    def get_legacy_func_count(self):
+        return self.legacy_func_count
+
+
+class ConfigInstance(ast.NodeVisitor):
+    def __init__(self):
+        self.count = 0
+
+    def visit_Call(self, node):
+        if isinstance(node.func, ast.Name):
+            name = node.func.id
+            if name == 'Config':
+                self.count += 1
+        self.generic_visit(node)
+
+    def get_count(self):
+        return self.count
+
+
+class FunctionConfigInstance(ast.NodeVisitor):
+    def __init__(self):
+        self.func_config_instance = dict.fromkeys(funcs, 0)
+
+    def visit_FunctionDef(self, node):
+        func_name = node.name
+        if func_name in funcs:
+            config_instance = ConfigInstance()
+            config_instance.visit(node)
+            self.func_config_instance[func_name] = config_instance.get_count()
+        self.generic_visit(node)
+
+    def get_func_config_instance(self):
+        return self.func_config_instance
+
 
 class TestConfigdInspect(TestCase):
     def setUp(self):
+        self.ast_list = []
+
         with open(INC_FILE) as f:
             self.inc_list = json.load(f)
 
-    @ignore_deprecation_warning
-    def test_signatures(self):
         for s in self.inc_list:
-            m = import_script(s)
-            for i in f_list:
-                f = getattr(m, i, None)
-                self.assertIsNotNone(f, f"'{s}': missing function '{i}'")
-                sig = signature(f)
-                par = sig.parameters
-                l = len(par)
-                self.assertEqual(l, 1,
-                        f"'{s}': '{i}' incorrect signature")
-                if i == 'get_config':
-                    for p in par.values():
-                        self.assertTrue(p.default is None,
-                                f"'{s}': '{i}' incorrect signature")
-
-    @ignore_deprecation_warning
-    def test_function_instance(self):
-        for s in self.inc_list:
-            m = import_script(s)
-            for i in f_list:
-                f = getattr(m, i, None)
-                if not f:
-                    continue
-                str_f = getsource(f)
-                # Regex not XXXConfig() T3108
-                n = len(re.findall(r'[^a-zA-Z]Config\(\)', str_f))
-                if i == 'get_config':
-                    self.assertEqual(n, 1,
-                            f"'{s}': '{i}' no instance of Config")
-                if i != 'get_config':
-                    self.assertEqual(n, 0,
-                            f"'{s}': '{i}' instance of Config")
-
-    @ignore_deprecation_warning
-    def test_file_instance(self):
-        for s in self.inc_list:
-            m = import_script(s)
-            str_m = getsource(m)
-            # Regex not XXXConfig T3108
-            n = len(re.findall(r'[^a-zA-Z]Config\(\)', str_m))
-            self.assertEqual(n, 1,
-                    f"'{s}' more than one instance of Config")
-
-    @ignore_deprecation_warning
+            s_path = f'{CONF_DIR}/{s}'
+            with open(s_path) as f:
+                s_str = f.read()
+            s_tree = ast.parse(s_str)
+            self.ast_list.append((s, s_tree))
+
+    def test_signatures(self):
+        for s, t in self.ast_list:
+            visitor = FunctionSig()
+            visitor.visit(t)
+            sig_lens = visitor.get_sig_lengths()
+
+            for f in funcs:
+                self.assertIsNotNone(sig_lens[f], f"'{s}': '{f}' missing")
+                self.assertEqual(sig_lens[f], 1, f"'{s}': '{f}' incorrect signature")
+
+            self.assertEqual(
+                visitor.get_config_default(),
+                None,
+                f"'{s}': 'get_config' incorrect signature",
+            )
+
+    def test_file_config_instance(self):
+        for s, t in self.ast_list:
+            visitor = ConfigInstance()
+            visitor.visit(t)
+            count = visitor.get_count()
+
+            self.assertEqual(count, 1, f"'{s}' more than one instance of Config")
+
+    def test_function_config_instance(self):
+        for s, t in self.ast_list:
+            visitor = FunctionConfigInstance()
+            visitor.visit(t)
+            func_config_instance = visitor.get_func_config_instance()
+
+            for f in funcs:
+                if f == 'get_config':
+                    self.assertTrue(
+                        func_config_instance[f] > 0,
+                        f"'{s}': '{f}' no instance of Config",
+                    )
+                    self.assertTrue(
+                        func_config_instance[f] < 2,
+                        f"'{s}': '{f}' more than one instance of Config",
+                    )
+                else:
+                    self.assertEqual(
+                        func_config_instance[f], 0, f"'{s}': '{f}' instance of Config"
+                    )
+
     def test_config_modification(self):
-        for s in self.inc_list:
-            m = import_script(s)
-            str_m = getsource(m)
-            n = str_m.count('my_set')
-            self.assertEqual(n, 0, f"'{s}' modifies config")
+        for s, t in self.ast_list:
+            visitor = LegacyCall()
+            visitor.visit(t)
+            legacy_func_count = visitor.get_legacy_func_count()
+
+            self.assertEqual(legacy_func_count, 0, f"'{s}' modifies config")