Expose rsonpath `MainEngine` and/or `Automaton` to avoid recompiling expressions

[amotl]

Hi again,

coming from one of our discussions about improving rsonpath-as-library use cases, we discovered a candidate that has already been evaluated positively:

@amotl said:

rsonpath currently does not provide a way to compile expressions for later reuse, like the jmespath, jq, and also the re modules are doing it? I recognize that this detail might not be required for typical CLI programs, which is the main target of rsonpath.

@V0ldek mentioned:

This is possible in the Rust rsonpath library (either compiling to an Automaton that can be serialized, or to a full MainEngine that is reusable). @charles-paperman could it be easily exposed in rsonpy as well?

@charles-paperman responded:

It is. I didn't bother packaging the compiled query with the interface but this should be rather straight forward to do. Feel free to open an issue on rsonpy repo and I will update it as soon as I have time :)

Thank you!

With kind regards,
Andreas.

[V0ldek]

@charles-paperman

It probably doesn't make sense to expose both, I'd aim for simplicity in the Python API (in the Rust one as well, but that's on me, the current API is a mess). So allow compiling a string into a MainEngine wrapper and then running on that.