Support opening data_objects in append mode

[hechth]

Currenty, even if a data object is oppenend with 'a' in the mode, it doesn!t seek the end before returnng the file

[d-w-moore]

Is that for pyfilesystem specifically?

[trel]

Can you provide example code that is not working for you?

[d-w-moore]

@trel @hechth Confirmed this is needed. I had thought that pyfilesystem did its own seek, but (more sensibly) it relies on the underlying object to implement 'a' correctly. I've run it through with pyfilesystem / irodsfs -- my own toy implementation -- and the changes in https://github.com/d-w-moore/python-irodsclient/tree/495.m, and that seems to correct it.

The basic problem is: ses.data_objects.open('aa.dat','a').write(b'_') should always extend the length of the object by seeking to the end automatically, and it doesn't. Instead, it's writing always at offset 0.

Which is a general problem needing a fix.

[trel]

okay, nice - we need a test to capture this new behavior, both in the positive and negative.

[trel]

i see the branch linked above and it has three commits, just need the PR created...

[d-w-moore]

i see the branch linked above and it has three commits, just need the PR created...

Now created: #516

[hechth]

@d-w-moore and @trel thanks a lot!