Add support for serde

[erickt]

This is an initial PR that adds support for the yet-to-be-released serde version 0.5.0, so please don't merge this in until that lands. I wanted to submit it to get your input on the design and if you see if there are any gaps in the implementation.

[TyOverby]

Wow! This will take me a while to read through, but it looks great! The one thing that I noticed right off the bat is that we could probably unify most of the unit tests. Instead of having test and test_serde, we could just have test, with proxy functions that use both implementations. Looks like you've already done this actually.

For example

fn proxy_encoded_size<T: ...>(obj: &T) -> usize {
    let ser_size = bincode::encoded_size(obj);
    let serde_size = bincode::serialized_size(obj);
    assert_eq(ser_size, serde_size);
    return ser_size;
}

I noticed that you already did that for the the_same function where you compare the existing implementation with the serde implementation.

I might hold off on reading the rest of the code until I can build and run it myself. At the very least I'll get a refresher on Serde tonight.

[TyOverby]

I am worried about how both of the implementations will be exposed though.

encode and to_vec are identical in terms of functionality, and so is decode and from_slice.

While they should be interchangeable, I think it'll be confusing to library users.

[pcwalton]

@TyOverby Ping. Servo really wants this. Is there a way I can help get this landed?

[TyOverby]

I won't be able to merge this until serde hits 0.5.0 on crates.io, but I will review the code later tonight. It would be great if using serde also sidestepped #41!

[TyOverby]

@erickt: I downloaded your patch and wired it up the path for Serde to your github repo so I could check it with 0.5.0, but there are a set of errors that indicate that serde can't be used with rust-1.0. I thought this was not the case?

$ cargo build
   Compiling aster v0.4.0
   Compiling quasi v0.3.1
   Compiling advapi32-sys v0.1.2
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:233:24: 233:48 error: failed to resolve. Could not find `Constness` in `syntax::ast`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:233             constness: ast::Constness::NotConst,
                                                                                                               ^~~~~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:233:24: 233:48 error: unresolved name `ast::Constness::NotConst`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:233             constness: ast::Constness::NotConst,
                                                                                                               ^~~~~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:247:16: 247:30 error: use of undeclared type name `ast::Constness`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:247     constness: ast::Constness,
                                                                                                       ^~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:261:26: 261:47 error: failed to resolve. Could not find `Constness` in `syntax::ast`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:261         self.constness = ast::Constness::Const;
                                                                                                                 ^~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:261:26: 261:47 error: unresolved name `ast::Constness::Const`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\item.rs:261         self.constness = ast::Constness::Const;
                                                                                                                 ^~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:28:16: 28:30 error: use of undeclared type name `ast::Constness`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:28     constness: ast::Constness,
                                                                                                        ^~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:50:24: 50:48 error: failed to resolve. Could not find `Constness` in `syntax::ast`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:50             constness: ast::Constness::NotConst,
                                                                                                                ^~~~~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:50:24: 50:48 error: unresolved name `ast::Constness::NotConst`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:50             constness: ast::Constness::NotConst,
                                                                                                                ^~~~~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:72:26: 72:47 error: failed to resolve. Could not find `Constness` in `syntax::ast`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:72         self.constness = ast::Constness::Const;
                                                                                                                  ^~~~~~~~~~~~~~~~~~~~~
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:72:26: 72:47 error: unresolved name `ast::Constness::Const`
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\aster-0.4.0\src\method.rs:72         self.constness = ast::Constness::Const;
                                                                                                                  ^~~~~~~~~~~~~~~~~~~~~
error: aborting due to 10 previous errors
Build failed, waiting for other jobs to finish...
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\quasi-0.3.1\src\lib.rs:11:43: 11:66 error: unstable feature
c:/Users/Ty\.cargo\registry\src\github.com-1ecc6299db9ec823\quasi-0.3.1\src\lib.rs:11 #![cfg_attr(not(feature = "with-syntex"), feature(rustc_private))]
                                                                                                                                ^~~~~~~~~~~~~~~~~~~~~~~
note: this feature may not be used in the stable release channel
error: aborting due to previous error
Could not compile `aster`.

To learn more, run the command again with --verbose.

[TyOverby]

Should this be an error inside SerializeError?

[TyOverby]

should this be impl_nums too?

[pcwalton]

@erickt Ping. If you don't have time for this, would you prefer that I pick up the patch and push it through?

[erickt]

@pcwalton: Just finally released 0.5.0 and updated this PR to build with it!

[TyOverby]

@erickt @pcwalton: Is this going to build with stable release? I thought the syntex crate was supposed to build on stable?

[TyOverby]

Ok, I got it building with stable (testing requires nightly, but that's acceptable).

There's a few changes that I'd like to make though, so I'll take this PR from here.

[TyOverby]

Yay merged! 🎉