This has, as far as I can see, two implications:
1. It must be possible to test for the presence of an extension
2. It must be possible to parse past 'unknown' extensions.
Stan's post brings to mind another consideration: some extensions may
themselves require extensions in order to function correctly. For instance,
an auto-file-by-favorite-color-of-sender extension may require the
ordered-list-of-favorite-colors extension.
You thus certainly have to have a test for the presence of an extension in
this case.
However, I think it's arguable that the second proposed requirement, that it
parse past unknown extensions, really has to apply. In the above instance, I
want the whole chain to fail so I don't accidentally file away by the wrong
set of colors or something.
This appears to me, on its face, to be the simpler approach and is more
likely to be safe in the sense that fewer unintended consequences are likely
to happen if the failure mode -- especially on extensions -- is simple. The
authoring filter agent ought simply to be told 'hey, you're yucking around
with some unknown extensions, go fix this' when a commit is attempted.
(And here Matt pauses to think of some disastrous FLAMES misfiling
episodes...ugh.)
- Matt