1 files changed, 71 insertions, 0 deletions
diff --git a/Lib/ast.py b/Lib/ast.py
index d7e51ab..031bab4 100644
--- a/Lib/ast.py
+++ b/Lib/ast.py
@@ -401,6 +401,77 @@ def walk(node):
         yield node
 
 
+def compare(
+    a,
+    b,
+    /,
+    *,
+    compare_attributes=False,
+):
+    """Recursively compares two ASTs.
+
+    compare_attributes affects whether AST attributes are considered
+    in the comparison. If compare_attributes is False (default), then
+    attributes are ignored. Otherwise they must all be equal. This
+    option is useful to check whether the ASTs are structurally equal but
+    might differ in whitespace or similar details.
+    """
+
+    def _compare(a, b):
+        # Compare two fields on an AST object, which may themselves be
+        # AST objects, lists of AST objects, or primitive ASDL types
+        # like identifiers and constants.
+        if isinstance(a, AST):
+            return compare(
+                a,
+                b,
+                compare_attributes=compare_attributes,
+            )
+        elif isinstance(a, list):
+            # If a field is repeated, then both objects will represent
+            # the value as a list.
+            if len(a) != len(b):
+                return False
+            for a_item, b_item in zip(a, b):
+                if not _compare(a_item, b_item):
+                    return False
+            else:
+                return True
+        else:
+            return type(a) is type(b) and a == b
+
+    def _compare_fields(a, b):
+        if a._fields != b._fields:
+            return False
+        for field in a._fields:
+            a_field = getattr(a, field)
+            b_field = getattr(b, field)
+            if not _compare(a_field, b_field):
+                return False
+        else:
+            return True
+
+    def _compare_attributes(a, b):
+        if a._attributes != b._attributes:
+            return False
+        # Attributes are always ints.
+        for attr in a._attributes:
+            a_attr = getattr(a, attr)
+            b_attr = getattr(b, attr)
+            if a_attr != b_attr:
+                return False
+        else:
+            return True
+
+    if type(a) is not type(b):
+        return False
+    if not _compare_fields(a, b):
+        return False
+    if compare_attributes and not _compare_attributes(a, b):
+        return False
+    return True
+
+
 class NodeVisitor(object):
     """
     A node visitor base class that walks the abstract syntax tree and calls a