Error reporting is limited when dict key is unhashable

[zaneb]

If you attempt to parse code that contains a mapping with an unhashable key, yaml raises a ConstructorError that tells the user exactly where the issue was. However, oyaml raises a TypeError, which may be missed by exception handling code expecting a ConstructorError, and which contains no information about where the problem occurred.

>>> def test():
...   try:
...     yaml.safe_load("{foo: bar}: baz")
...   except Exception as e:
...     print("%s: %s" % (type(e).__name__, e))
... 
>>> import yaml
>>> test()
ConstructorError: while constructing a mapping
found unacceptable key (unhashable type: 'dict')
  in "<string>", line 1, column 1:
    {foo: bar}: baz
    ^
>>> import oyaml
>>> test()
TypeError: unhashable type: 'OrderedDict'

[wimglenn]

What version(s)? Can not reproduce with oyaml v0.8 / PyYAML 5.1 / Python 3.7.2 (linux). I get the same richer exception context for both pyyaml and oyaml.

Edit: I can reproduce it on 2.7

[zaneb]

Anything before 3.6 I expect. oyaml doesn't patch the Loader after that.

[wimglenn]

Hmm, it's not really amenable to monkeypatching here since the mapping type is just a literal in the local scope. I really need this to be more like def construct_mapping(self, node, deep=False, factory=dict):. But I'll see what I can do. Thanks for the report!

[zaneb]

Yes, it's a pain. You have to choose between inefficiency and reimplementing a bunch of internal logic :(

[wimglenn]

There could also be an ast rewrite 😈
Anyway, the try/re-raise in #18 seems an acceptable solution, time will tell if travis agrees ..