generate options types from fdb.options

[yjh0502]

• I used error-chain for error handling because I'm familiar with it. It might better to change it to failure, as other sub-crates do.
• I embedded fdb.options file into source. Please let me know if you have any preferred option.
• FdbScope::ty and FdbOption::ty return String instead of taking Write (for maybe Formatter?) as a mutable argument. The code looks dirty but it works :(
• fdb_network_set_options and similar APIs take length and pointer as arguments, so next step might be generating apply() function which call underlying C API for each enum types.

[bluejekyll]

This is awesome! I haven't even got a license up yet :)

I was planning an Apache 2.0/MIT if that's ok with you, I'll add that to repo then we can merge that into this PR so that we have all that squared away.

---

• On error-chain: I just pushed an FdbError type last night, it's based on Failure which is going to replace error-chain in most use-cases in Rust. I think you're generator can skip generating errors and instead just use the hand-written type? https://github.com/bluejekyll/foundationdb-rs/blob/master/foundationdb/src/error.rs

• fdb.options: I have no opinion at-the-moment, we can clean this up later... I don't think this is a bad option, but we probably want to track a version somehow.

• "The code looks dirty but it works": All code starts out dirty, then we learn what we want and make it better ;) your decisions here seem fine to me.

• fdb_network_set_options: I almost started working on the wrapper API for this last night. We'll have to see what happens with that.

---

Thanks, again for the PR. Let me get the LICENSE squared away, and then address the FdbError question and then let's go from there.

[bluejekyll]

Failure is quite nice and simple. For the generator, you can get away with just using format_err! and returning the failure::Error type. in the result type, example:

fn example() -> Result<Type, failure::Error> {
   Err(format_err!("my failure message: {}", extra_info)
}

Can we switch to that instead? I believe most of Rust is going to be going in this direction.

[yjh0502]

I changed it to failure.

[bluejekyll]

Can you look at error::FdbError in the foundationdb crate? We should maybe remove my hand-rolled version.

[yjh0502]

I replaced FdbErrorPredicate with options::ErrorPredicate. I'm not sure about name of fn code() -> fdb::FDBErrorPredicate. It's okay for other enum types which might have seperated value like String, but for ErrorPredicate case fn value() -> ... sounds better.

[bluejekyll]

Technically these values are fdb::FDBErrorPredicate_FDB_ERROR_PREDICATE_MAYBE_COMMITTED, rather than the raw value. Not sure if this is something the generator could write instead?

[yjh0502]

I just tried to change those values to generated one, but there are some mismatches between names on fdb.options and names on fdb_c.h. Here's a list.

https://gist.github.com/yjh0502/cd19273e15464e5e2c377fc9f3ce3e03

• Some of them are just singular/plural problem, for example WATCH/WATCHES, BYTE/BYTES. I can handle it with some brute-force replace rules.
• It seems that options with hidden=true is not available on c header. I filtered those options.
• There's one remaining non-regular case, FDBMutationType_FDB_MUTATION_TYPE_SET_VERSIONSTAMPED_KEY, which should not be converted to ..._KEYS. I just hard-coded the case :(

[yjh0502]

Thanks for the feedback!

• I'm happy with Apache 2.0/MIT
• For error types, I just error-chain mainly for ensure!/bail! macros which helps debugging during iteration. I'll replace it into hand-written error types.

For fdb_network_set_options things, I added a unsafe fn apply() which is a helper functions. You can use those functions for initial prototyping :)

• 53c9f45#diff-cd3b1f98c824b08ddc1d3579abe50a0dR371
• 53c9f45#diff-cd3b1f98c824b08ddc1d3579abe50a0dR130

[bluejekyll]

Thanks again for the PR, if this is ready I'll merge it in.

I'm working on travis scripts right now, so we should get some testing options.

[bluejekyll]

Thanks again for the PR, this is a massive help!