TatSu: yaml.representer.RepresenterError when dumping to YAML - python-3.x

Question

I have a object model generated by TatSu after doing a successful parse. The model dumps to stdout using JSON format OK. But when I try to dump it to YAML, I get a RepresenterError exception. I am not sure how to solve this. The object model is generated internally by TatSu. Can anyone shed any light on how to potentially resolve this error?
Using python 3.7.0 with TatSu v4.4.0 with pyyaml 5.1.2.
My code:
import sys
import json
import datetime
import tatsu
from tatsu.ast import asjson
from tatsu.objectmodel import Node
from tatsu.semantics import ModelBuilderSemantics
from tatsu.exceptions import FailedParse
class ModelBase(Node):
pass
class MyModelBuilderSemantics(ModelBuilderSemantics):
def __init__(self, context=None, types=None):
types = [
t for t in globals().values()
if type(t) is type and issubclass(t, ModelBase)
] + (types or [])
super(MyModelBuilderSemantics, self).__init__(context=context, types=types)
def main():
sys.setrecursionlimit(10000)
grammar = open('STIL1999.ebnf.working').read()
parser = tatsu.compile(grammar, semantics=MyModelBuilderSemantics(), asmodel=True)
assert (parser is not None)
try:
start = datetime.datetime.now()
ast = parser.parse(open(sys.argv[1]).read(), filename=sys.argv[1])
finish = datetime.datetime.now()
print('Total = %s' % (finish - start).total_seconds())
print(json.dumps(asjson(ast), indent=2))
except FailedParse as e:
print('Parse error : %s' % e.message)
print(e.buf.line_info(e.pos))
return 1
from tatsu.yaml import ast_dump
ast_dump(ast, stream=open('foo.yaml', 'w'))
return 0
if __name__ == '__main__':
sys.exit(main())
The output:
Total = 0.007043
{
"__class__": "StilSession",
"version": {
"ver": 1.0
},
"header": {
"__class__": "Header",
"objs": [
{
"k": "Title",
"v": "foo.gz"
},
{
"k": "Date",
"v": "Mon Nov 4 02:48:48 2019"
},
{
"k": "Source",
"v": "foo.gz"
},
{
"k": "History",
"objs": [
{
"__class__": "Annotation",
"ann": " This is a test "
}
]
}
]
},
"blocks": []
}
Traceback (most recent call last):
File "./run.py", line 57, in <module>
sys.exit(main())
File "./run.py", line 52, in main
ast_dump(ast, stream=open('foo.yaml', 'w'))
File "/sw_tools/anaconda3/lib/python3.7/site-packages/tatsu/yaml.py", line 50, i
n ast_dump
return dump(data, object_pairs_hook=AST, **kwargs)
File "/sw_tools/anaconda3/lib/python3.7/site-packages/tatsu/yaml.py", line 33, i
n dump
**kwds
File "/sw_tools/anaconda3/lib/python3.7/site-packages/yaml/__init__.py", line 29
0, in dump
return dump_all([data], stream, Dumper=Dumper, **kwds)
File "/sw_tools/anaconda3/lib/python3.7/site-packages/yaml/__init__.py", line 27
8, in dump_all
dumper.represent(data)
File "/sw_tools/anaconda3/lib/python3.7/site-packages/yaml/representer.py", line
27, in represent
node = self.represent_data(data)
File "/sw_tools/anaconda3/lib/python3.7/site-packages/yaml/representer.py", line
58, in represent_data
node = self.yaml_representers[None](self, data)
File "/sw_tools/anaconda3/lib/python3.7/site-packages/yaml/representer.py", line
231, in represent_undefined
raise RepresenterError("cannot represent an object", data)
yaml.representer.RepresenterError: ('cannot represent an object', <tatsu.synth.StilSession object at 0x7ffff6
8e8f98>)

Answer 1

This issue was resolved by the OP in TatSu pull request #146