There are several issues in ast.dump() with incompletely initialized node. Some fields and attributes of AST nodes are optional, but creating an AST node without them leads ast.dump() to fail or to produce incorrect result.

1. With annotate_fields=False ast.dump() outputs subnodes as positional arguments of the node constructor.

>>> ast.dump(ast.Raise(exc=ast.Name(id='a', ctx=ast.Load()), cause=ast.Name(id='b', ctx=ast.Load())), annotate_fields=False)
"Raise(Name('a', Load()), Name('b', Load()))"

But if miss the optional exc field it outputs incorrect output:

>>> ast.dump(ast.Raise(cause=ast.Name(id='a', ctx=ast.Load())), annotate_fields=False)
"Raise(Name('a', Load()))"

which is not distinguished from the case when you pass only the exc field and miss the cause field (both are optional):

>>> ast.dump(ast.Raise(exc=ast.Name(id='a', ctx=ast.Load())), annotate_fields=False)
"Raise(Name('a', Load()))"

2. The documentation of ast.dump() says that its result with annotate_fields=True is impossible to evaluate, but this is not true, because keyword arguments are supported by AST node constructors.

3. Attributes end_lineno and end_col_offset are optional, but if you miss them ast.dump() with include_attributes=True will fail:

>>> ast.dump(ast.Raise(lineno=3, col_offset=4), include_attributes=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/serhiy/py/cpython3.8/Lib/ast.py", line 126, in dump
    return _format(node)
  File "/home/serhiy/py/cpython3.8/Lib/ast.py", line 118, in _format
    rv += ', '.join('%s=%s' % (a, _format(getattr(node, a)))
  File "/home/serhiy/py/cpython3.8/Lib/ast.py", line 118, in <genexpr>
    rv += ', '.join('%s=%s' % (a, _format(getattr(node, a)))
AttributeError: 'Raise' object has no attribute 'end_lineno'

4. Even if you specify all attributes, the output looks weird if you do not specify any field (note a space after "("):

>>> ast.dump(ast.Raise(lineno=3, col_offset=4, end_lineno=3, end_col_offset=24), include_attributes=True)
'Raise( lineno=3, col_offset=4, end_lineno=3, end_col_offset=24)'

New changeset e64f948e762a6b9fd02e2902ccf42438df6fcb61 by Serhiy Storchaka in branch 'master':
bpo-37950: Fix ast.dump() when call with incompletely initialized node. (GH-15510)
https://github.com/python/cpython/commit/e64f948e762a6b9fd02e2902ccf42438df6fcb61

New changeset d3d2650cf84e6be0f84d6d0d538999d1e0cfdd43 by Miss Islington (bot) in branch '3.7':
bpo-37950: Fix ast.dump() when call with incompletely initialized node. (GH-15510)
https://github.com/python/cpython/commit/d3d2650cf84e6be0f84d6d0d538999d1e0cfdd43

New changeset 097eae5b9b4801d34bb900c01b5e6a80f028bc12 by Serhiy Storchaka in branch '3.8':
[3.8] bpo-37950: Fix ast.dump() when call with incompletely initialized node. (GH-15510) (GH-15582)
https://github.com/python/cpython/commit/097eae5b9b4801d34bb900c01b5e6a80f028bc12