contracts: move schema gen boilerplate to a binary crate

[uint]

Closes #755

This should make the layout of a contract a bit less confusing. How's this look?

[hashedone]

I have one problem with this approach, and it's serious - see the comment. It obviously applies to all instances of this dependency.

[hashedone]

We don't want this in a normal build. Technically it would probably get optimized out, but still would prolong compilation and is not wanted there in general. The workaround for this is probably to:

• make this dependency optional
• add a feature schema-bin enabling this dependency
• add a [[bin]] section like:

[[bin]]
name = "schema"
path = "src/bin/main.rs"
required-features = ["schema-bin"]

This actually might be a good reason to extract the dependency to examples... I mean it still seems better as a binary, but it requires more boilerplate in Cargo.toml

[uint]

It definitely gets optimized out - I tested it before.

This change is coming anyway. I already moved the schema dependency to regular deps in cosmwasm-std 1.1.0 contracts in this PR: CosmWasm/cosmwasm#1339 I also mentioned this problem in the PR, but didn't receive feedback against it or suggested solutions.

I know this could still be changed by adding a feature flag and doing something like:

#[cfg_attr(feature = "schema", derive(QueryResponses))]
pub enum QueryMsg {
    #[cfg_attr(feature = "schema", returns(VerifierResponse))]
    Verifier {},
    ...
}

But I'm not sure I'm really sold on this. Is the extra complexity worth better compilation times?

[hashedone]

I am mostly worried about some garbage left in the output Wasm binary so it increases in size. Did you check if wasm binary size after this change is not affected? If so then build times are secondary and it's mergeable. I am not happy about increasing complexity of dependency tree, but also its not a huge problem (at least yet).

[uint]

AFAIR, I checked the size of the Wasm binary after running it through rust-optimizer and it was identical to main, but I'm happy to double-check it before merging this.

[uint]

@hashedone For the cosmwasm-vm stuff (check_contract, module_size, etc), I'm tempted to set up a new package called cosmwasm-toolbox and move all of them there as binary crates. That way we avoid extra dependencies in cosmwasm-vm, but also avoid adding more feature flags, right? But that's a separate PR for another time.

[hashedone]

@uint I would personally create a separate package for each of those utils, so if we publish them you just do cargo install cw-check-contract or smthng. Also integration with cargo might be a thing (like calling cargo check_contract to ensure build wasm binary and check it.

[ethanfrey]

In the end, the only real effect is changing --example to --bin?
Or does this have other positive improvements? Or needed as a future building block?

[uint]

Well, it also removes the schema gen code from the 'examples' directory so that a person new to CosmWasm contracts doesn't have to wonder "what the hell?" when looking at the source of one and trying to figure out what's what.

[uint]

Recently Dan mentioned this seemed odd and asked if we can rename the examples directory. When I first looked at how schemas are generated in contracts, I also had a "what the hell" moment.

[ethanfrey]

Okay, no blocker my side. Just seemed odd. But I guess I made this weird setup and an used to it.

If it makes CosmWasm users happy, let's do it.

[maurolacy]

LGTM. I guess we'll have to change this in all the other repos for consistency.

[uint]

LGTM. I guess we'll have to change this in all the other repos for consistency.

I think it mainly matters for the "public goods" ones where people are likely to look for inspiration, like here, cosmwasm, cw-template. For other projects it's a nice-to-have IMO.

[uint]

Rebased

[webmaster128]

Is there a reason for keeping those unchanged?

$ find . -name schema.rs | grep examples/schema.rs
./packages/cw1/examples/schema.rs
./packages/cw20/examples/schema.rs
./packages/cw3/examples/schema.rs
./packages/cw4/examples/schema.rs
./packages/cw1155/examples/schema.rs