Added flag to ignore aliases/anchors

[engnadeau]

• Fixes Disable Aliases/Anchors #103

[engnadeau]

Only Python 2.6 fails, but it's EOL.

[engnadeau]

This PR will depend on #105

[perlpunk]

I think this can be useful.
However, when using with cyclic references, we run into an endless loop. This is a problem with the existing code, so adding this flag doesn't introduce this problem, but makes it easy to reproduce:

import yaml

string = "&node [ a, b, *node ]"
data = yaml.load(string)
print(data)
out = yaml.dump(data, ignore_aliases=True)
print(out)

...
RecursionError: maximum recursion depth exceeded while calling a Python object

The code in represent_data should remember the nodes it has already visited and output null in that case.

I might have some time to fix this, but not sure when.

[perlpunk]

On the other hand, if the desired behaviour is to expand all aliases, then we'd have to live with the possibility of an endless loop. The documentation should warn about this then.

[engnadeau]

Yes, my intention is to have no aliases at all, simplifying the YAML markup.

[engnadeau]

closing stale PR