Map fields with empty string as key are handled incorrectly

[mkosieradzki]

protobuf.js version: 6.8.0

UPDATED:
Current codegen for map-fields when string key is empty is incorrect.

ORIGINAL:
Current codegen for map-fields is invalid. It assumes that map keys are non empty (!) strings (!!).

1. Map CAN have empty string as indices.
2. Map CAN be indexed by something different than string...

Both parsing and JS representation (Object instead of Map) are broken.

[dcodeIO]

It does not assume that protobuf map keys are strings, it just makes any map keys strings on the JS-side because that's how it works in JavaScript. For example, long ints are converted to an 8 bytes hash string and there are utility functions to convert / generate these keys. Other values are simply converted to strings to be usable as a JS object key.

[mkosieradzki]

@dcodeIO Thanks and sorry, I have jumped too quick to conclusions. So only empty strings are mishandled.

[mkosieradzki]

I have fixed the codegen in my fork and I will create a PR soon.