Allow registering ops without specifying the full schema

[smessmer]

Stack:
    :white_circle:  #19280 Split function schema parser from operator  💛
    :white_circle:  #19281 Fixing function schema parser for Android  💛
    :white_circle:  #19282 Move function schema parser to ATen/core build target  💚
    :white_circle:  #19283 String-based schemas in op registration API  💛
    :white_circle:  #19284 Allow ops without tensor args if only fallback kernel exists  💛
    :white_circle:  #19285 Add either type  💛
    :black_circle:  #19286 Allow registering ops without specifying the full schema  💛
    :white_circle:  #19287 Use string based schema for exposing caffe2 ops  💛
    :white_circle:  #19288 Add some tests  💛
    :white_circle:  #19289 Optional inputs and outputs  💛
    :white_circle:  #19290 Add tests for argument types  💛

The operator registration API now allows registering an operator by only giving the operator name and not the full operator schema,
as long as the operator schema can be inferred from the kernel function.

Differential Revision: D14931921

[dzhulgakov]

Looks pretty idiomatic :)

Given that you just check whether '(' is in the schema - couldn't we just use str.find() first and then call one method or another? That way we could have saved ourselves need for Either.

But since you've already added it, I don't mind

[smessmer]

We'd still need the either type because - even if using str.find(), I'd like that logic to live inside the parser header and be returned by parseSchemaOrName(). There will likely be other places where users can specify either a full schema or just a name, and I don't want to repeat the str.find() logic there.

[facebook-github-bot]

This pull request has been merged in 5ca22cc.