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| # Integration | ||
|
|
||
| If you want to use Wasm in your own app, here is how you can get this working | ||
| quickly and easily. First, check to make sure you fit the pre-requisites, | ||
| then integrate the `x/wasm` module as described below, and finally, you | ||
| can add custom messages and queries to your custom Go/SDK modules, exposing | ||
| them to any chain-specific contract. | ||
|
|
||
| ## Prerequisites | ||
|
|
||
| The pre-requisites of integrating `x/wasm` into your custom app is to be using | ||
| a compatible version of the Cosmos SDK, and to accept some limits to the | ||
| hardware it runs on. | ||
|
|
||
| | wasmd | Cosmos SDK | | ||
| |:-----:|:----------:| | ||
| | v0.7 | v0.38 | | ||
| | v0.8 | v0.38 | | ||
|
|
||
| We currently only support Intel/AMD64 CPUs and OSX or Linux (with glibc - not muslc like alpine). | ||
| This limit comes from the Rust dll we use to run the wasm code. There are open issues | ||
| for adding [ARM support](https://github.com/CosmWasm/go-cosmwasm/issues/53), | ||
| adding [Windows support](https://github.com/CosmWasm/go-cosmwasm/issues/28), | ||
| and [compiling static binaries](https://github.com/CosmWasm/go-cosmwasm/issues/45), so it works on both glibc and muslc systems. | ||
| However, these issues are not high on the roadmap and unless you are championing | ||
| them, please count on the current limits for the near future. | ||
|
|
||
| ## Quick Trial | ||
|
|
||
| The simplest way to try out CosmWasm is simply to run `wasmd` out of the box, | ||
| and focus on writing, uploading, and using your custom contracts. There is | ||
| plenty that can be done there, and lots to learn. | ||
|
|
||
| Once you are happy with it and want to use a custom Cosmos SDK app, | ||
| you may consider simply forking `wasmd`. *I highly advise against this*. | ||
| You should try one of the methods below. | ||
|
|
||
| ## Integrating wasmd | ||
|
|
||
| ### As external module | ||
|
|
||
| The simplest way to use `wasmd` is just to import `x/wasm` and wire it up | ||
| in `app.go`. You now have access to the whole module and you custom modules | ||
| running side by side. (But the CosmWasm contracts will only have access | ||
| to `bank` and `staking`... more below on [customization](#Adding-Custom-Hooks)). | ||
|
|
||
| The requirement here is that you have imported the standard sdk modules | ||
| from the Cosmos SDK, and enabled them in `app.go`. If so, you can just look | ||
| at [`wasmd/app/app.go`](https://github.com/CosmWasm/wasmd/blob/master/app/app.go#) | ||
| for how to do so (just search there for lines with `wasm`). | ||
|
|
||
| ### Copied into your app | ||
|
|
||
| Sometimes, however, you will need to copy `x/wasm` into your app. This should | ||
| be in limited cases, and makes upgrading more difficult, so please take the | ||
| above path if possible. This is required if you have either disabled some key | ||
| SDK modules in your app (eg. using PoA not staking and need to disable those | ||
| callbacks and feature support), or if you have copied in the core `x/*` modules | ||
| from the Cosmos SDK into your application and customized them somehow. | ||
|
|
||
| In either case, your best approach is to copy the `x/wasm` module from the | ||
| latest release into your application. Your goal is to make **minimal changes** | ||
| in this module, and rather add your customizations in a separate module. | ||
| This is due to the fact that you will have to copy and customize `x/wasm` | ||
| from upstream on all future `wasmd` releases, and this should be as simple | ||
| as possible. | ||
|
|
||
| If, for example, you have forked the standard SDK libs, you just want to | ||
| change the imports (from eg. `github.com/cosmos/cosmos-sdk/x/bank` to | ||
| `github.com/YOUR/APP/x/bank`), and adjust any calls if there are compiler | ||
| errors due to differing APIs (maybe you use Decimals not Ints for currencies?). | ||
|
|
||
| By the end of this, you should be able to run the standard CosmWasm contracts | ||
| in your application, alongside all your custom logic. | ||
|
|
||
| ## Adding custom hooks | ||
|
|
||
| Once you have gotten this integration working and are happy with the | ||
| flexibility it offers you, you will probably start wishing for deeper | ||
| integration with your custom SDK modules. "It sure is nice to have custom | ||
| tokens with a bonding curve from my native token, but I would love | ||
| to trade them on the exchange I wrote as a Go module. Or maybe use them | ||
| to add options to the exchange." | ||
|
|
||
| At this point, you need to dig down deeper and see how you can add this | ||
| power without forking either CosmWasm or `wasmd`. | ||
|
|
||
| ### Calling contracts from native code | ||
|
|
||
| This is perhaps the easiest part. Let's say your native exchange module | ||
| wants to call into a token that lives as a CosmWasm module. You need to | ||
| pass the `wasm.Keeper` into your `exchange.Keeper`. If you know the format | ||
| for sending messages and querying the contract (exported as json schema | ||
| from each contract), and have a way of configuring addresses of supported | ||
| token contracts, your exchange code can simply call `wasm.Keeper.Execute` | ||
| with a properly formatted message to move funds, or `wasm.Keeper.SmartQuery` | ||
| to check balances. | ||
|
|
||
| If you look at the unit tests in [`x/wasm/internal/keeper`](https://github.com/CosmWasm/wasmd/tree/master/x/wasm/internal/keeper), | ||
| it should be pretty straight forward. | ||
|
|
||
| ### Extending the Contract Interface | ||
|
|
||
| If you want to let the contracts access your native modules, the first | ||
| step is to define a set of Messages and Queries that you want to expose, | ||
| and then add them as `CosmosMsg::Custom` and `QueryRequest::Custom` | ||
| variants. You can see an example of the [bindings for Terra](https://github.com/CosmWasm/terra-contracts/tree/master/packages/bindings). | ||
|
|
||
| Once you have those bindings, use them to build a | ||
| [simple contact using much of the API](https://github.com/CosmWasm/terra-contracts/tree/master/contracts/maker). | ||
| Don't worry too much about the details, this should be usable, but mainly | ||
| you will want to upload it to your chain and use for integration tests | ||
| with your native Cosmos SDK modules. Once that is solid, then add more | ||
| and more complex contracts. | ||
|
|
||
| You will then likely want to add a `mocks` package so you can provide | ||
| mocks for the functionality of your native modules when unit testing | ||
| the contracts (provide static data for exchange rates when your contracts | ||
| query it). You can see an example of [mocks for Terra contracts](https://github.com/CosmWasm/terra-contracts/tree/master/packages/mocks). | ||
|
|
||
| What these three steps provide is basically a chain-specific extension to the CosmWasm contract SDK. | ||
| Any CosmWasm contract can import you library (bindings and mocks) and easily get started using | ||
| your custom, chain-specific extensions just as easily as using the standard CosmWasm interfaces. | ||
| What is left is actually wiring them up in your chain so they work as desired. | ||
|
|
||
| Note, in order to ensure that no one tries to run the contracts on an unsupported chain, | ||
| you will want to include a `requires_XYZ` directive in your `bindings` library, this will | ||
| mean that only blockchain apps that explicitly declare their support for the `XYZ` extensions | ||
| (please rename XYZ to your project name) will allow the contract to be uploaded, and others | ||
| get error messages upon upload, not while running a critical feature later on. | ||
| You just need to add [a line like this](https://github.com/CosmWasm/terra-contracts/blob/master/packages/bindings/src/lib.rs#L13-L16) | ||
| to your binding library to add the requirement to any contract that imports your `bindings` lib. | ||
|
|
||
| ### Calling into the SDK | ||
|
|
||
| Before I show how this works, I want to remind you, if you have copied `x/wasm`, | ||
| please **do not make these changes to `x/wasm`**. | ||
|
|
||
| We will add a new module, eg. `x/contracts`, that will contain custom | ||
| bindings between CosmWasm contracts and your native modules. There are two entry points | ||
| for you to use. The first is | ||
| [`CustomQuerier`](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/query_plugins.go#L35), | ||
| which allows you to handle your custom queries. The second is | ||
| [`CustomEncoder`](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/handler_plugin.go#L30) | ||
| which allows you to convert the `CosmosMsg::Custom(YourMessage)` types to `[]sdk.Msg` to be dispatched. | ||
|
|
||
| Writing stubs for these is rather simple. You can look at the `reflect_test.go` file to see this in action. | ||
| In particular, here [we define a `CustomQuerier`](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/reflect_test.go#L355-L385), | ||
| and here [we define a `CustomHandler`](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/reflect_test.go#L303-L353). | ||
| This code is responsible to take `json.RawMessage` from the raw bytes serialized from your custom types in rust and parse it into | ||
| Go structs. Then take these go structs and properly convert them for your custom SDK modules. | ||
|
|
||
| You can look at the implementations for the `staking` module to see how to build these for non-trivial | ||
| cases, including passing in the `Keeper` via a closure. Here we | ||
| [encode staking messages](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/handler_plugin.go#L114-L192). | ||
| Note that withdraw returns 2 messages, which is an option you can use if needed to translate into native messages. | ||
| When we [handle staking queries](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/x/wasm/internal/keeper/query_plugins.go#L109-L172) | ||
| we take in a `Keeper in the closure` and dispatch the custom `QueryRequest` from the contract to the native `Keeper` interface, | ||
| then encodes a response. When defining the return types, note that for proper parsing in the Rust contract, you | ||
| should properly name the JSON fields and use the `omitempty` keyword if Rust expects `Option<T>`. You must also use | ||
| `omitempty` and pointers for all fields that correspond to a Rust `enum`, so exactly one field is serialized. | ||
|
|
||
| ### Wiring it all together | ||
|
|
||
| Once you have writen and tested these custom callbacks for your module, you need to enable it in your application. | ||
| The first step is to write an integration test with a contract compiled with your custom SDK to ensure it works properly, | ||
| then you need to configure this in `app.go`. | ||
|
|
||
| For the test cases, you must | ||
| [define the supported feature set](https://github.com/CosmWasm/wasmd/blob/ade03a1d39a9b8882e9a1ce80572d39d57bb9bc3/x/wasm/internal/keeper/reflect_test.go#L52) | ||
| to include your custom name (remember `requires_XYZ` above?). Then, when creating `TestInput`, | ||
| you can [pass in your custom encoder and querier](https://github.com/CosmWasm/wasmd/blob/ade03a1d39a9b8882e9a1ce80572d39d57bb9bc3/x/wasm/internal/keeper/reflect_test.go#L52). | ||
| Run a few tests with your compiled contract, ideally exercising the majority of the interfaces to ensure that all parsing between the contract and | ||
| the SDK is implemented properly. | ||
|
|
||
| Once you have tested this and are happy with the results, you can wire it up in `app.go`. | ||
| Just edit [the default `NewKeeper` constructor](https://github.com/CosmWasm/wasmd/blob/v0.8.0-rc1/app/app.go#L257-L258) | ||
| to have the proper `supportedFeatures` and pass in the `CustomEncoder` and `CustomQuerier` as the last two arguments to `NewKeeper`. | ||
| Now you can compile your chain and upload your custom contracts on it. |
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