Fix __debug__ comparison check

CHANGELOG.md

@@ -10,6 +10,11 @@ and will output source code compatible with the version of the interpreter it is
 This means that if you minify code written for Python 3.11 using python-minifier running with Python 3.12,
 the minified code may only run with Python 3.12.
 
+## [3.1.1] - 2025-12-11
+
+### Fixed
+- The remove debug transform could incorrectly remove if branches that did not test `__debug__`
+
 ## [3.1.0] - 2025-10-10
 
 ### Added
@@ -306,6 +311,7 @@ the minified code may only run with Python 3.12.
 - python-minifier package
 - pyminify command
 
+[3.1.1]: https://github.com/dflook/python-minifier/compare/3.1.0...3.1.1
 [3.1.0]: https://github.com/dflook/python-minifier/compare/3.0.0...3.1.0
 [3.0.0]: https://github.com/dflook/python-minifier/compare/2.11.3...3.0.0
 [2.11.3]: https://github.com/dflook/python-minifier/compare/2.11.2...2.11.3

src/python_minifier/transforms/remove_debug.py

@@ -27,18 +27,38 @@ def can_remove(self, node):
         if not isinstance(node, ast.If):
             return False
 
-        if isinstance(node.test, ast.Name) and node.test.id == '__debug__':
-            return True
+        def is_simple_debug_check():
+            # Simple case: if __debug__:
+            if isinstance(node.test, ast.Name) and node.test.id == '__debug__':
+                return True
+            return False
 
-        if isinstance(node.test, ast.Compare) and len(node.test.ops) == 1 and isinstance(node.test.ops[0], ast.Is) and self.constant_value(node.test.comparators[0]) is True:
-            return True
+        def is_truthy_debug_comparison():
+            # Comparison case: if __debug__ is True / False / etc.
+            if not isinstance(node.test, ast.Compare):
+                return False
 
-        if isinstance(node.test, ast.Compare) and len(node.test.ops) == 1 and isinstance(node.test.ops[0], ast.IsNot) and self.constant_value(node.test.comparators[0]) is False:
-            return True
+            if not isinstance(node.test.left, ast.Name):
+                return False
 
-        if isinstance(node.test, ast.Compare) and len(node.test.ops) == 1 and isinstance(node.test.ops[0], ast.Eq) and self.constant_value(node.test.comparators[0]) is True:
-            return True
+            if node.test.left.id != '__debug__':
+                return False
 
+            if len(node.test.ops) == 1:
+                op = node.test.ops[0]
+                comparator_value = self.constant_value(node.test.comparators[0])
+
+                if isinstance(op, ast.Is) and comparator_value is True:
+                    return True
+                if isinstance(op, ast.IsNot) and comparator_value is False:
+                    return True
+                if isinstance(op, ast.Eq) and comparator_value is True:
+                    return True
+
+            return False
+
+        if is_simple_debug_check() or is_truthy_debug_comparison():
+            return True
         return False
 
     def suite(self, node_list, parent):

test/test_remove_debug.py

@@ -167,3 +167,61 @@ def test_no_remove_falsy_debug(condition):
     expected_ast = ast.parse(expected)
     actual_ast = remove_debug(source)
     compare_ast(expected_ast, actual_ast)
+
+
+@pytest.mark.parametrize(
+    'condition', [
+        '__sandwich__',
+        '__sandwich__ is True',
+        '__sandwich__ is False',
+        '__sandwich__ is not False',
+        '__sandwich__ == True',
+        '__sandwich__ == __debug__',
+        '__sandwich() == True',
+        'func() is True',
+        'some_call(a, b) is True',
+        'obj.method() is True',
+        'obj.attr is True',
+        'True is something',
+        'True == something',
+    ]
+)
+def test_no_remove_not_debug(condition):
+    source = '''
+value = 10
+
+# Not a __debug__ test
+if ''' + condition + ''':
+  value += 1
+
+print(value)
+    '''
+
+    expected = source
+
+    expected_ast = ast.parse(expected)
+    actual_ast = remove_debug(source)
+    compare_ast(expected_ast, actual_ast)
+
+
+def test_no_remove_is_true_in_elif_chain():
+    """Regression test for issue #142 - if/elif/else with 'is True' comparisons"""
+    source = '''
+def check_is_internet_working(c):
+    url, url_hostname = get_url_and_url_hostname(c)
+
+    if is_internet_working_socket_test(c, url_hostname) is True:
+        c.is_internet_connected = True
+    elif is_internet_working_urllib_open(c, url) is True:
+        c.is_internet_connected = True
+    else:
+        c.is_internet_connected = False
+
+    return c.is_internet_connected
+'''
+
+    expected = source
+
+    expected_ast = ast.parse(expected)
+    actual_ast = remove_debug(source)
+    compare_ast(expected_ast, actual_ast)