Harmonize gast.dump behavior across versions, following py3.13 behavior

gast/__init__.py

@@ -1,3 +1,3 @@
 from .gast import *
 from .version import __version__
-from ast import NodeVisitor, NodeTransformer, iter_fields, dump
+from ast import NodeVisitor, NodeTransformer, iter_fields

gast/gast.py

@@ -469,3 +469,95 @@ def increment_lineno(node, n=1):
         if 'end_lineno' in child._attributes:
             child.end_lineno = (getattr(child, 'end_lineno', 0) or 0) + n
     return node
+
+if _sys.version_info.major == 3 and _sys.version_info.minor >= 13:
+    dump = _ast.dump
+else:
+    # Code import from Lib/ast.py
+    #
+    # minor changes: getattr(x, y, ...) is None => getattr(x, y, 42) is None
+    #
+    def dump(
+        node, annotate_fields=True, include_attributes=False,
+        # *,  # removed for compatibility with python2 :-/
+        indent=None, show_empty=False,
+    ):
+        """
+        Return a formatted dump of the tree in node.  This is mainly useful for
+        debugging purposes.  If annotate_fields is true (by default),
+        the returned string will show the names and the values for fields.
+        If annotate_fields is false, the result string will be more compact by
+        omitting unambiguous field names.  Attributes such as line
+        numbers and column offsets are not dumped by default.  If this is wanted,
+        include_attributes can be set to true.  If indent is a non-negative
+        integer or string, then the tree will be pretty-printed with that indent
+        level. None (the default) selects the single line representation.
+        If show_empty is False, then empty lists and fields that are None
+        will be omitted from the output for better readability.
+        """
+        def _format(node, level=0):
+            if indent is not None:
+                level += 1
+                prefix = '\n' + indent * level
+                sep = ',\n' + indent * level
+            else:
+                prefix = ''
+                sep = ', '
+            if isinstance(node, AST):
+                cls = type(node)
+                args = []
+                args_buffer = []
+                allsimple = True
+                keywords = annotate_fields
+                for name in node._fields:
+                    try:
+                        value = getattr(node, name)
+                    except AttributeError:
+                        keywords = True
+                        continue
+                    if value is None and getattr(cls, name, 42) is None:
+                        keywords = True
+                        continue
+                    if (
+                        not show_empty
+                        and (value is None or value == [])
+                        # Special cases:
+                        # `Constant(value=None)` and `MatchSingleton(value=None)`
+                        and not isinstance(node, (Constant, MatchSingleton))
+                    ):
+                        args_buffer.append(repr(value))
+                        continue
+                    elif not keywords:
+                        args.extend(args_buffer)
+                        args_buffer = []
+                    value, simple = _format(value, level)
+                    allsimple = allsimple and simple
+                    if keywords:
+                        args.append('%s=%s' % (name, value))
+                    else:
+                        args.append(value)
+                if include_attributes and node._attributes:
+                    for name in node._attributes:
+                        try:
+                            value = getattr(node, name)
+                        except AttributeError:
+                            continue
+                        if value is None and getattr(cls, name, 42) is None:
+                            continue
+                        value, simple = _format(value, level)
+                        allsimple = allsimple and simple
+                        args.append('%s=%s' % (name, value))
+                if allsimple and len(args) <= 3:
+                    return '%s(%s)' % (node.__class__.__name__, ', '.join(args)), not args
+                return '%s(%s%s)' % (node.__class__.__name__, prefix, sep.join(args)), False
+            elif isinstance(node, list):
+                if not node:
+                    return '[]', True
+                return '[%s%s]' % (prefix, sep.join(_format(x, level)[0] for x in node)), False
+            return repr(node), True
+
+        if not isinstance(node, AST):
+            raise TypeError('expected AST, got %r' % node.__class__.__name__)
+        if indent is not None and not isinstance(indent, str):
+            indent = ' ' * indent
+        return _format(node)[0]

tests/test_api.py

@@ -5,12 +5,8 @@
 import sys
 
 
-if sys.version_info >= (3, 13):
-    def dump(node):
-        return gast.dump(node, show_empty=True)
-else:
-    def dump(node):
-        return gast.dump(node)
+def dump(node):
+    return gast.dump(node, show_empty=True)
 
 
 class APITestCase(unittest.TestCase):

tests/test_compat.py

@@ -4,12 +4,8 @@
 import sys
 
 
-if sys.version_info >= (3, 13):
-    def dump(node):
-        return gast.dump(node, show_empty=True)
-else:
-    def dump(node):
-        return gast.dump(node)
+def dump(node):
+    return gast.dump(node, show_empty=True)
 
 
 class CompatTestCase(unittest.TestCase):

tests/test_py3_12.py

@@ -4,12 +4,8 @@
 import gast
 import sys
 
-if sys.version_info >= (3, 13):
-    def dump(node):
-        return gast.dump(node, show_empty=True)
-else:
-    def dump(node):
-        return gast.dump(node)
+def dump(node):
+    return gast.dump(node, show_empty=True)
 
 
 class Python3_12TestCase(unittest.TestCase):