Migrating Contracts

This guide explains what is needed to upgrade contracts when migrating over major releases of cosmwasm. Note that you can also view the complete CHANGELOG to understand the differences.

1.0.0-beta -> 1.0.0 (unreleased)

The minimum Rust supported version is 1.53.0. Verify your Rust version is >= 1.53.0 with: rustc --version.

Simplify mock_dependencies calls with empty balance:

     #[test]
     fn instantiate_fails() {
-        let mut deps = mock_dependencies(&[]);
+        let mut deps = mock_dependencies();

         let msg = InstantiateMsg {};
         let info = mock_info("creator", &coins(1000, "earth"));

Or use the new mock_dependencies_with_balance if you need a balance:

     #[test]
     fn migrate_cleans_up_data() {
-        let mut deps = mock_dependencies(&coins(123456, "gold"));
+        let mut deps = mock_dependencies_with_balance(&coins(123456, "gold"));

         // store some sample data
         deps.storage.set(b"foo", b"bar");

0.16 -> 1.0.0-beta

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "1.0.0-beta"
cosmwasm-storage = "1.0.0-beta"
# ...

[dev-dependencies]
cosmwasm-schema = "1.0.0-beta"
cosmwasm-vm = "1.0.0-beta"
# ...

Use type Record instead of Pair

// before
use cosmwasm_std::Pair;

// after
use cosmwasm_std::Record;

Replace cosmwasm_std::create_entry_points! and cosmwasm_std::create_entry_points_with_migration! with #[entry_point] annotations. See the 0.13 -> 0.14 entry where #[entry_point] was introduced.

If your chain provides a custom queries, add the custom query type as a generic argument to cosmwasm_std::Deps, DepsMut, OwnedDeps and QuerierWrapper. Otherwise it defaults to Empty. E.g.

 #[entry_point]
 pub fn instantiate(
-    deps: DepsMut,
+    deps: DepsMut<CyberQueryWrapper>,
     _env: Env,
     info: MessageInfo,
     msg: InstantiateMsg,
@@ -38,112 +35,95 @@ pub fn instantiate(
 }

 #[entry_point]
-pub fn query(deps: Deps, _env: Env, msg: QueryMsg) -> StdResult<Binary> {
+pub fn query(deps: Deps<CyberQueryWrapper>, _env: Env, msg: QueryMsg) ->   StdResult<Binary> {
     match msg {

 pub struct CyberQuerier<'a> {
-    querier: &'a QuerierWrapper<'a>,
+    querier: &'a QuerierWrapper<'a, CyberQueryWrapper>,
 }

 impl<'a> CyberQuerier<'a> {
-    pub fn new(querier: &'a QuerierWrapper) -> Self {
+    pub fn new(querier: &'a QuerierWrapper<'a, CyberQueryWrapper>) -> Self {
         CyberQuerier { querier }
     }
 }

Replace QuerierWrapper::custom_query with QuerierWrapper::query which is now fully typed:

-let res: CyberlinksAmountResponse = self.querier.custom_query(&request.into())?;
+let res: CyberlinksAmountResponse = self.querier.query(&request.into())?;

See cybercongress/cw-cyber#2 for a complete example.

Integration tests

Add new transaction field to Env when creating a custom mock env:

@@ -19,6 +19,7 @@

 use cosmwasm_std::{
     coins, Addr, BlockInfo, Coin, ContractInfo, Env, MessageInfo, Response, Timestamp,
+    TransactionInfo,
 };
 use cosmwasm_storage::to_length_prefixed;
 use cosmwasm_vm::testing::{instantiate, mock_info, mock_instance};
@@ -52,6 +53,7 @@ fn mock_env_info_height(signer: &str, sent: &[Coin], height: u64, time: u64) ->
         contract: ContractInfo {
             address: Addr::unchecked(MOCK_CONTRACT_ADDR),
         },
+        transaction: Some(TransactionInfo { index: 3 }),
     };
     let info = mock_info(signer, sent);
     return (env, info);

Gas usage increases by a factor of approximately 150_000. Adapt your tests accordingly.

0.15 -> 0.16

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.16.0"
cosmwasm-storage = "0.16.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.16.0"
cosmwasm-vm = "0.16.0"
# ...

The attr function now accepts arguments that implement Into<String> rather than ToString. This means that "stringly" types like &str are still accepted, but others (like numbers or booleans) have to be explicitly converted to strings; you can use the to_string method (from the std::string::ToString trait) for that.
```
  let steal_funds = true;
- attr("steal_funds", steal_funds),
+ attr("steal_funds", steal_funds.to_string()),
```
It also means that &&str is no longer accepted.
The iterator feature in cosmwasm-std, cosmwasm-vm and cosmwasm-storage is now enabled by default. If you want to use it, you don't have to explicitly enable it anymore.

If you don't want to use it, you have to disable default features when depending on cosmwasm-std. Example:
```
- cosmwasm-std = { version = "0.15.0" }
+ cosmwasm-std = { version = "0.16.0", default-features = false }
```

The Event::attr setter has been renamed to Event::add_attribute - this is for consistency with other types, like Response.

- let event = Event::new("ibc").attr("channel", "connect");
+ let event = Event::new("ibc").add_attribute("channel", "connect");

Response can no longer be built using a struct literal. Please use Response::new as well as relevant builder-style setters to set the data.

This is a step toward better API stability.

  #[entry_point]
  pub fn migrate(deps: DepsMut, env: Env, msg: MigrateMsg) -> StdResult<Response> {
      // ...

      let send = BankMsg::Send {
          to_address: msg.payout.clone(),
          amount: balance,
      };
      let data_msg = format!("burnt {} keys", count).into_bytes();

-     Ok(Response {
-         messages: vec![SubMsg::new(send)],
-         attributes: vec![attr("action", "burn"), attr("payout", msg.payout)],
-         events: vec![],
-         data: Some(data_msg.into()),
-     })
+     Ok(Response::new()
+         .add_message(send)
+         .add_attribute("action", "burn")
+         .add_attribute("payout", msg.payout)
+         .set_data(data_msg))
  }

- Ok(Response {
-     data: Some((old_size as u32).to_be_bytes().into()),
-     ..Response::default()
- })
+ Ok(Response::new().set_data((old_size as u32).to_be_bytes()))

- let res = Response {
-     messages: msgs,
-     attributes: vec![attr("action", "reflect_subcall")],
-     events: vec![],
-     data: None,
- };
- Ok(res)
+ Ok(Response::new()
+     .add_attribute("action", "reflect_subcall")
+     .add_submessages(msgs))

For IBC-enabled contracts only: constructing IbcReceiveResponse and IbcBasicResponse follows the same principles now as Response above.

  pub fn ibc_packet_receive(
      deps: DepsMut,
      env: Env,
      msg: IbcPacketReceiveMsg,
  ) -> StdResult<IbcReceiveResponse> {
      // ...

-     Ok(IbcReceiveResponse {
-         acknowledgement,
-         messages: vec![],
-         attributes: vec![],
-         events: vec![Event::new("ibc").attr("packet", "receive")],
-     })
+     Ok(IbcReceiveResponse::new()
+         .set_ack(acknowledgement)
+         .add_event(Event::new("ibc").add_attribute("packet", "receive")))
  }

For IBC-enabled contracts only: IBC entry points have different signatures. Instead of accepting bare packets, channels and acknowledgements, all of those are wrapped in a Msg type specific to the given entry point. Channels, packets and acknowledgements have to be unpacked from those.

  #[entry_point]
- pub fn ibc_channel_open(_deps: DepsMut, _env: Env, channel: IbcChannel) -> StdResult<()> {
+ pub fn ibc_channel_open(_deps: DepsMut, _env: Env, msg: IbcChannelOpenMsg) -> StdResult<()> {
+     let channel = msg.channel();

      // do things
  }

  #[entry_point]
  pub fn ibc_channel_connect(
      deps: DepsMut,
      env: Env,
-     channel: IbcChannel,
+     msg: IbcChannelConnectMsg,
  ) -> StdResult<IbcBasicResponse> {
+     let channel = msg.channel();

      // do things
  }

  #[entry_point]
  pub fn ibc_channel_close(
      deps: DepsMut,
      env: Env,
-     channel: IbcChannel,
+     msg: IbcChannelCloseMsg,
  ) -> StdResult<IbcBasicResponse> {
+     let channel = msg.channel();

      // do things
  }

  #[entry_point]
  pub fn ibc_packet_receive(
      deps: DepsMut,
      env: Env,
-     packet: IbcPacket,
+     msg: IbcPacketReceiveMsg,
  ) -> StdResult<IbcReceiveResponse> {
+     let packet = msg.packet;

      // do things
  }

  #[entry_point]
  pub fn ibc_packet_receive(
      deps: DepsMut,
      env: Env,
-     ack: IbcAcknowledgementWithPacket,
+     msg: IbcPacketReceiveMsg,
  ) -> StdResult<IbcBasicResponse> {
      // They are the same struct just a different name
      let ack = msg;

      // do things
  }

  #[entry_point]
  pub fn ibc_packet_timeout(
      deps: DepsMut,
      env: Env,
-     packet: IbcPacket,
+     msg: IbcPacketTimeoutMsg,
  ) -> StdResult<IbcBasicResponse> {
+     let packet = msg.packet;

      // do things
  }

0.14 -> 0.15

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.15.0"
cosmwasm-storage = "0.15.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.15.0"
cosmwasm-vm = "0.15.0"
# ...

Combine messages and submessages on the Response object. The new format uses messages: Vec<SubMsg<T>>, so copy submessages content, and wrap old messages using SubMsg::new. Here is how to change messages:

let send = BankMsg::Send { to_address, amount };

// before
let res = Response {
  messages: vec![send.into()],
  ..Response::default()
}

// after
let res = Response {
  messages: vec![SubMsg::new(send)],
  ..Response::default()
}

// alternate approach
let mut res = Response::new();
res.add_message(send);

And here is how to change submessages:

// before
let sub_msg = SubMsg {
  id: INIT_CALLBACK_ID,
  msg: msg.into(),
  gas_limit: None,
  reply_on: ReplyOn::Success,
};
let res = Response {
  submessages: vec![sub_msg],
  ..Response::default()
};

// after
let msg = SubMsg::reply_on_success(msg, INIT_CALLBACK_ID);
let res = Response {
  messages: vec![msg],
  ..Response::default()
};

// alternate approach
let msg = SubMsg::reply_on_success(msg, INIT_CALLBACK_ID);
let mut res = Response::new();
res.add_submessage(msg);

Note that this means you can mix "messages" and "submessages" in any execution order. You are no more restricted to doing "submessages" first.

Rename the send field to funds whenever constructing a WasmMsg::Execute or WasmMsg::Instantiate value.

  let exec = WasmMsg::Execute {
      contract_addr: coin.address.into(),
      msg: to_binary(&msg)?,
-     send: vec![],
+     funds: vec![],
  };

Uint128 field can no longer be constructed using a struct literal. Call Uint128::new (or Uint128::zero) instead.

- const TOKENS_PER_WEIGHT: Uint128 = Uint128(1_000);
- const MIN_BOND: Uint128 = Uint128(5_000);
+ const TOKENS_PER_WEIGHT: Uint128 = Uint128::new(1_000);
+ const MIN_BOND: Uint128 = Uint128::new(5_000);

- assert_eq!(escrow_balance, Uint128(0));
+ assert_eq!(escrow_balance, Uint128::zero());

If constructing a Response using struct literal syntax, add the events field.

  Ok(Response {
      messages: vec![],
      attributes,
+     events: vec![],
      data: None,
  })

For IBC-enabled contracts only: You need to adapt to the new IbcAcknowledgementWithPacket structure and use the embedded data field:

// before
pub fn ibc_packet_ack(
  deps: DepsMut,
  env: Env,
  ack: IbcAcknowledgement,
) -> StdResult<Response> {
  let res: AcknowledgementMsg = from_slice(&ack.acknowledgement)?;
  // ...
}

// after
pub fn ibc_packet_ack(
  deps: DepsMut,
  env: Env,
  ack: IbcAcknowledgementWithPacket,
) -> StdResult<Response> {
  let res: AcknowledgementMsg = from_slice(&ack.acknowledgement.data)?;
  // ...
}

You also need to update the constructors in test code. Below we show how to do so both for JSON data as well as any custom binary format:

// before (JSON)
let ack = IbcAcknowledgement {
  acknowledgement: to_binary(&AcknowledgementMsg::Ok(())).unwrap()
  original_packet: packet,
};

// after (JSON)
let ack = IbcAcknowledgementWithPacket {
    acknowledgement: IbcAcknowledgement::encode_json(&AcknowledgementMsg::Ok(())).unwrap(),
    original_packet: packet,
};

// before (Custom binary data)
let acknowledgement = vec![12, 56, 78];
let ack = IbcAcknowledgement {
  acknowledgement: Binary(acknowledgement),
  original_packet: packet,
};

// after (Custom binary data)
let acknowledgement = vec![12, 56, 78];
let ack = IbcAcknowledgement {
  acknowledgement: IbcAcknowledgement::new(acknowledgement),
  original_packet: packet,
};

0.13 -> 0.14

The minimum Rust supported version for 0.14 is 1.51.0. Verify your Rust version is >= 1.51.0 with: rustc --version

Update CosmWasm and schemars dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.14.0"
cosmwasm-storage = "0.14.0"
schemars = "0.8.1"
# ...

[dev-dependencies]
cosmwasm-schema = "0.14.0"
cosmwasm-vm = "0.14.0"
# ...

Rename the init entry point to instantiate. Also, rename InitMsg to InstantiateMsg.
Rename the handle entry point to execute. Also, rename HandleMsg to ExecuteMsg.
Rename InitResponse, HandleResponse and MigrateResponse to Response. The old names are still supported (with a deprecation warning), and will be removed in the next version. Also, you'll need to add the submessages field to Response.

Remove from_address from BankMsg::Send, which is now automatically filled with the contract address:

// before
ctx.add_message(BankMsg::Send {
    from_address: env.contract.address,
    to_address: to_addr,
    amount: balance,
});

// after
ctx.add_message(BankMsg::Send {
    to_address: to_addr,
    amount: balance,
});

Use the new entry point system. From lib.rs remove

#[cfg(target_arch = "wasm32")]
cosmwasm_std::create_entry_points!(contract);

// or

#[cfg(target_arch = "wasm32")]
cosmwasm_std::create_entry_points_with_migration!(contract);

Then add the macro attribute #[entry_point] to your contract.rs as follows:

use cosmwasm_std::{entry_point, … };

// …

#[entry_point]
pub fn init(
    _deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    _msg: InitMsg,
) -> StdResult<Response> {
    // …
}

#[entry_point]
pub fn execute(
    _deps: DepsMut,
    _env: Env,
    _info: MessageInfo,
    _msg: ExecuteMsg,
) -> StdResult<Response> {
    // …
}

// only if you have migrate
#[entry_point]
pub fn migrate(
    deps: DepsMut,
    env: Env,
    _info: MessageInfo,
    msg: MigrateMsg,
) -> StdResult<Response> {
    // …
}

#[entry_point]
pub fn query(_deps: Deps, _env: Env, _msg: QueryMsg) -> StdResult<QueryResponse> {
    // …
}

Since Response contains a data field, converting Context into Response always succeeds.

// before
pub fn init(deps: DepsMut, env: Env, info: MessageInfo, msg: InitMsg) -> Result<InitResponse, HackError> {
    // …
    let mut ctx = Context::new();
    ctx.add_attribute("Let the", "hacking begin");
    Ok(ctx.try_into()?)
}

// after
pub fn init(deps: DepsMut, env: Env, info: MessageInfo, msg: InitMsg) -> Result<Response, HackError> {
    // …
    let mut ctx = Context::new();
    ctx.add_attribute("Let the", "hacking begin");
    Ok(ctx.into())
}

Remove the info: MessageInfo field from the migrate entry point:
```
// Before
pub fn migrate(
    deps: DepsMut,
    env: Env,
    _info: MessageInfo,
    msg: MigrateMsg,
) -> StdResult<MigrateResponse> {
  // ...
}

// After
pub fn migrate(deps: DepsMut, env: Env, msg: MigrateMsg) -> StdResult<Response> {
  // ...
}
```
MessageInfo::funds was always empty since MsgMigrateContract does not have a funds field. MessageInfo::sender should not be needed for authentication because the chain checks permissions before calling migrate. If the sender's address is needed for anything else, this should be expressed as part of the migrate message.

Add mutating helper methods to Response that can be used instead of creating a Context that is later converted to a response:

// before
pub fn handle_impl(deps: DepsMut, env: Env, info: MessageInfo) -> Result<Response, ContractError> {
    // ...

    // release counter_offer to creator
    let mut ctx = Context::new();
    ctx.add_message(BankMsg::Send {
        to_address: state.creator,
        amount: state.counter_offer,
    });

    // release collateral to sender
    ctx.add_message(BankMsg::Send {
        to_address: state.owner,
        amount: state.collateral,
    });

    // ..

    ctx.add_attribute("action", "execute");
    Ok(ctx.into())
}


// after
pub fn execute_impl(deps: DepsMut, env: Env, info: MessageInfo) -> Result<Response, ContractError> {
    // ...

    // release counter_offer to creator
    let mut resp = Response::new();
    resp.add_message(BankMsg::Send {
        to_address: state.creator,
        amount: state.counter_offer,
    });

    // release collateral to sender
    resp.add_message(BankMsg::Send {
        to_address: state.owner,
        amount: state.collateral,
    });

    // ..

    resp.add_attribute("action", "execute");
    Ok(resp)
}

Use type Pair instead of KV

// before
use cosmwasm_std::KV;

// after
use cosmwasm_std::Pair;

If necessary, add a wildcard arm to the match of now non-exhaustive message types BankMsg, BankQuery, WasmMsg and WasmQuery.

HumanAddr has been deprecated in favour of simply String. It never added any significant safety bonus over String and was just a marker type. The new type Addr was created to hold validated addresses. Those can be created via Addr::unchecked, Api::addr_validate, Api::addr_humanize and JSON deserialization. In order to maintain type safety, deserialization into Addr must only be done from trusted sources like a contract's state or a query response. User inputs must be deserialized into String. This new Addr type makes it easy to use human readable addresses in state:

With pre-validated Addr from MessageInfo:

// before
pub struct State {
    pub owner: CanonicalAddr,
}

let state = State {
    owner: deps.api.canonical_address(&info.sender /* of type HumanAddr */)?,
};


// after
pub struct State {
    pub owner: Addr,
}
let state = State {
    owner: info.sender.clone() /* of type Addr */,
};

With user input in msg:

// before
pub struct State {
    pub verifier: CanonicalAddr,
    pub beneficiary: CanonicalAddr,
    pub funder: CanonicalAddr,
}

deps.storage.set(
    CONFIG_KEY,
    &to_vec(&State {
        verifier: deps.api.canonical_address(&msg.verifier /* of type HumanAddr */)?,
        beneficiary: deps.api.canonical_address(&msg.beneficiary /* of type HumanAddr */)?,
        funder: deps.api.canonical_address(&info.sender /* of type HumanAddr */)?,
    })?,
);

// after
pub struct State {
    pub verifier: Addr,
    pub beneficiary: Addr,
    pub funder: Addr,
}

deps.storage.set(
    CONFIG_KEY,
    &to_vec(&State {
        verifier: deps.api.addr_validate(&msg.verifier /* of type String */)?,
        beneficiary: deps.api.addr_validate(&msg.beneficiary /* of type String */)?,
        funder: info.sender /* of type Addr */,
    })?,
);

The existing CanonicalAddr remains unchanged and can be used in cases in which a compact binary representation is desired. For JSON state this does not save much data (e.g. the bech32 address cosmos1pfq05em6sfkls66ut4m2257p7qwlk448h8mysz takes 45 bytes as direct ASCII and 28 bytes when its canonical representation is base64 encoded). For fixed length database keys CanonicalAddr remains handy though.

Replace StakingMsg::Withdraw with DistributionMsg::SetWithdrawAddress and DistributionMsg::WithdrawDelegatorReward. StakingMsg::Withdraw was a shorthand for the two distribution messages. However, it was unintuitive because it did not set the address for one withdraw only but for all following withdrawls. Since withdrawls are triggered by different events such as validators changing their commission rate, an address that was set for a one-time withdrawl would be used for future withdrawls not considered by the contract author.

If the contract never set a withdraw address other than the contract itself (env.contract.address), you can simply replace StakingMsg::Withdraw with DistributionMsg::WithdrawDelegatorReward. It is then never changed from the default. Otherwise you need to carefully track what the current withdraw address is. A one-time change can be implemented by emitted 3 messages:
1. SetWithdrawAddress { address: recipient } to temporarily change the recipient
2. WithdrawDelegatorReward { validator } to do a manual withdrawl from the given validator
3. SetWithdrawAddress { address: env.contract.address.into() } to change it back for all future withdrawls
The block time in env.block.time is now a Timestamp which stores nanosecond precision. env.block.time_nanos was removed. If you need the compnents as before, use
```
let seconds = env.block.time.nanos() / 1_000_000_000;
let nsecs = env.block.time.nanos() % 1_000_000_000;
```

0.12 -> 0.13

The minimum Rust supported version for 0.13 is 1.47.0. Verify your Rust version is >= 1.47.0 with: rustc --version

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.13.0"
cosmwasm-storage = "0.13.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.13.0"
cosmwasm-vm = "0.13.0"
# ...

0.11 -> 0.12

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.12.0"
cosmwasm-storage = "0.12.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.12.0"
cosmwasm-vm = "0.12.0"
# ...

In your contract's .cargo/config remove --features backtraces, which is now available in Rust nightly only:

@@ -1,6 +1,6 @@
 [alias]
 wasm = "build --release --target wasm32-unknown-unknown"
 wasm-debug = "build --target wasm32-unknown-unknown"
-unit-test = "test --lib --features backtraces"
+unit-test = "test --lib"
 integration-test = "test --test integration"
 schema = "run --example schema"

In order to use backtraces for debugging, run RUST_BACKTRACE=1 cargo +nightly unit-test --features backtraces.

Rename the type Extern to Deps, and radically simplify the init/handle/migrate/query entrypoints. Rather than &mut Extern<S, A, Q>, use DepsMut. And instead of &Extern<S, A, Q>, use Deps. If you ever pass eg. foo<A: Api>(api: A) around, you must now use dynamic trait pointers: foo(api: &dyn Api). Here is the quick search-replace guide on how to fix contract.rs:

In production (non-test) code:
- <S: Storage, A: Api, Q: Querier> => ``
- &mut Extern<S, A, Q> => DepsMut
- &Extern<S, A, Q> => Deps
- &mut deps.storage => deps.storage where passing into state.rs helpers
- &deps.storage => deps.storage where passing into state.rs helpers
On the top, remove use cosmwasm_std::{Api, Extern, Querier, Storage}. Add use cosmwasm_std::{Deps, DepsMut}.

In test code only:
- &mut deps, => deps.as_mut(),
- &deps, => deps.as_ref(),
You may have to add use cosmwasm_std::{Storage} if the compile complains about the trait

If you use cosmwasm-storage, in state.rs:
- <S: Storage> => ``
- <S: ReadonlyStorage> => ``
- <S, => <
- &mut S => &mut dyn Storage
- &S => &dyn Storage
If you have any references to ReadonlyStorage left after the above, please replace them with Storage

0.10 -> 0.11

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.11.0"
cosmwasm-storage = "0.11.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.11.0"
cosmwasm-vm = "0.11.0"
# ...

Contracts now support any custom error type E: ToString + From<StdError>. Previously this has been StdError, which you can still use. However, you can now create a much more structured error experience for your unit tests that handels exactly the error cases of your contract. In order to get a convenient implementation for ToString and From<StdError>, we use the crate thiserror, which needs to be added to the contracts dependencies in Cargo.toml. To create the custom error, create an error module src/errors.rs as follows:
```
use cosmwasm_std::{CanonicalAddr, StdError};
use thiserror::Error;

// thiserror implements Display and ToString if you
// set the `#[error("…")]` attribute for all cases
#[derive(Error, Debug)]
pub enum MyCustomError {
    #[error("{0}")]
    // let thiserror implement From<StdError> for you
    Std(#[from] StdError),
    // this is whatever we want
    #[error("Permission denied: the sender is not the current owner")]
    NotCurrentOwner {
        expected: CanonicalAddr,
        actual: CanonicalAddr,
    },
    #[error("Messages empty. Must reflect at least one message")]
    MessagesEmpty,
}
```
Then add mod errors; to src/lib.rs and use crate::errors::MyCustomError; to src/contract.rs. Now adapt the return types as follows:
- fn init: Result<InitResponse, MyCustomError>,
- fn migrate (if you have it): Result<MigrateResponse, MyCustomError>,
- fn handle: Result<HandleResponse, MyCustomError>,
- fn query: Result<Binary, MyCustomError>.
If one of your funtions does not use the custom error, you can continue to use StdError as before. I.e. you can have handle returning Result<HandleResponse, MyCustomError> and query returning StdResult<Binary>.

You can have a top-hevel init/migrate/handle/query that returns a custom error but some of its implementations only return errors from the standard library (StdResult<HandleResponse> aka. Result<HandleResponse, StdError>). Then use Ok(std_result?) to convert between the result types. E.g.
```
pub fn handle<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    msg: HandleMsg,
) -> Result<HandleResponse, StakingError> {
    match msg {
        // conversion to Result<HandleResponse, StakingError>
        HandleMsg::Bond {} => Ok(bond(deps, env)?),
        // this already returns Result<HandleResponse, StakingError>
        HandleMsg::_BondAllTokens {} => _bond_all_tokens(deps, env),
    }
}
```
or
```
pub fn init<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    msg: InitMsg,
) -> Result<InitResponse, HackError> {
    // …

    let mut ctx = Context::new();
    ctx.add_attribute("Let the", "hacking begin");
    Ok(ctx.try_into()?)
}
```
Once you got familiar with the concept, you can create different error types for each of the contract's functions.

You can also try a different error library than thiserror. The staking development contract shows how this would look like using snafu.
Change order of arguments such that storage is always first followed by namespace in Bucket::new, Bucket::multilevel, ReadonlyBucket::new, ReadonlyBucket::multilevel, PrefixedStorage::new, PrefixedStorage::multilevel, ReadonlyPrefixedStorage::new, ReadonlyPrefixedStorage::multilevel, bucket, bucket_read, prefixed and prefixed_read.
```
// before
let mut bucket = bucket::<_, Data>(b"data", &mut store);

// after
let mut bucket = bucket::<_, Data>(&mut store, b"data");
```

Rename InitResponse::log, MigrateResponse::log and HandleResponse::log to InitResponse::attributes, MigrateResponse::attributes and HandleResponse::attributes. Replace calls to log with attr:

// before
Ok(HandleResponse {
  log: vec![log("action", "change_owner"), log("owner", owner)],
  ..HandleResponse::default()
})

// after
Ok(HandleResponse {
  attributes: vec![attr("action", "change_owner"), attr("owner", owner)],
  ..HandleResponse::default()
})

Rename Context::add_log to Context::add_attribute:

// before
let mut ctx = Context::new();
ctx.add_log("action", "release");
ctx.add_log("destination", &to_addr);

// after
let mut ctx = Context::new();
ctx.add_attribute("action", "release");
ctx.add_attribute("destination", &to_addr);

Add result type to Bucket::update and Singleton::update:

// before
bucket.update(b"maria", |mayd: Option<Data>| {
  let mut d = mayd.ok_or(StdError::not_found("Data"))?;
  old_age = d.age;
  d.age += 1;
  Ok(d)
})

// after
bucket.update(b"maria", |mayd: Option<Data>| -> StdResult<_> {
  let mut d = mayd.ok_or(StdError::not_found("Data"))?;
  old_age = d.age;
  d.age += 1;
  Ok(d)
})

Remove all canonical_length arguments from mock APIs in tests:

// before
let mut deps = mock_dependencies(20, &[]);
let mut deps = mock_dependencies(20, &coins(123456, "gold"));
let deps = mock_dependencies_with_balances(20, &[(&rich_addr, &rich_balance)]);
let api = MockApi::new(20);

// after
let mut deps = mock_dependencies(&[]);
let mut deps = mock_dependencies(&coins(123456, "gold"));
let deps = mock_dependencies_with_balances(&[(&rich_addr, &rich_balance)]);
let api = MockApi::default();

Add MessageInfo as separate arg after Env for init, handle, migrate. Add Env arg to query. Use info.sender instead of env.message.sender and info.sent_funds rather than env.message.sent_funds. Just changing the function signatures of the 3-4 export functions should be enough, then the compiler will warn you anywhere you use env.message

// before
pub fn init<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    msg: InitMsg,
) {
    deps.storage.set(
        CONFIG_KEY,
        &to_vec(&State {
            verifier: deps.api.canonical_address(&msg.verifier)?,
            beneficiary: deps.api.canonical_address(&msg.beneficiary)?,
            funder: deps.api.canonical_address(&env.message.sender)?,
        })?,
    );
}

// after
pub fn init<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    _env: Env,
    info: MessageInfo,
    msg: InitMsg,
) {
    deps.storage.set(
        CONFIG_KEY,
        &to_vec(&State {
            verifier: deps.api.canonical_address(&msg.verifier)?,
            beneficiary: deps.api.canonical_address(&msg.beneficiary)?,
            funder: deps.api.canonical_address(&info.sender)?,
        })?,
    );
}

Test code now has mock_info which takes the same args mock_env used to. You can just pass mock_env() directly into the function calls unless you need to change height/time.

One more object to pass in for both unit and integration tests. To do this quickly, I just highlight all copies of env and replace them with info (using Ctrl+D in VSCode or Alt+J in IntelliJ). Then I select all deps, info sections and replace that with deps, mock_env(), info. This fixes up all init and handle calls, then just add an extra mock_env() to the query calls.

// before: unit test
let env = mock_env(creator.as_str(), &[]);
let res = init(&mut deps, env, msg).unwrap();

let query_response = query(&deps, QueryMsg::Verifier {}).unwrap();

// after: unit test
let info = mock_info(creator.as_str(), &[]);
let res = init(&mut deps, mock_env(), info, msg).unwrap();

let query_response = query(&deps, mock_env(), QueryMsg::Verifier {}).unwrap();

// before: integration test
let env = mock_env("creator", &coins(1000, "earth"));
let res: InitResponse = init(&mut deps, env, msg).unwrap();

let query_response = query(&mut deps, QueryMsg::Verifier {}).unwrap();

// after: integration test
let info = mock_info("creator", &coins(1000, "earth"));
let res: InitResponse = init(&mut deps, mock_env(), info, msg).unwrap();

let query_response = query(&mut deps, mock_env(), QueryMsg::Verifier {}).unwrap();

0.9 -> 0.10

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.10.0"
cosmwasm-storage = "0.10.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.10.0"
cosmwasm-vm = "0.10.0"
# ...

Integration tests:

Calls to Api::human_address and Api::canonical_address now return a pair of result and gas information. Change
```
// before
verifier: deps.api.canonical_address(&verifier).unwrap(),

// after
verifier: deps.api.canonical_address(&verifier).0.unwrap(),
```
The same applies for all calls of Querier and Storage.

All Tests:

All usages of mock_env will have to remove the first argument (no need of API).

// before
let env = mock_env(&deps.api, "creator", &coins(1000, "earth"));

// after
let env = mock_env("creator", &coins(1000, "earth"));

Contracts:

All code that uses message.sender or contract.address should deal with HumanAddr not CanonicalAddr. Many times this means you can remove a conversion step.

0.8 -> 0.9

Update CosmWasm dependencies in Cargo.toml (skip the ones you don't use):

[dependencies]
cosmwasm-std = "0.9.0"
cosmwasm-storage = "0.9.0"
# ...

[dev-dependencies]
cosmwasm-schema = "0.9.0"
cosmwasm-vm = "0.9.0"
# ...

lib.rs:

The C export boilerplate can now be reduced to the following code (see e.g. in hackatom/src/lib.rs):

mod contract; // contains init, handle, query
// maybe additional modules here

#[cfg(target_arch = "wasm32")]
cosmwasm_std::create_entry_points!(contract);

Contract code and uni tests:

cosmwasm_storage::get_with_prefix, cosmwasm_storage::set_with_prefix, cosmwasm_storage::RepLog::commit, cosmwasm_std::ReadonlyStorage::get, cosmwasm_std::ReadonlyStorage::range, cosmwasm_std::Storage::set and cosmwasm_std::Storage::remove now return the value directly that was wrapped in a result before.
Error creator functions are now in type itself, e.g. StdError::invalid_base64 instead of invalid_base64. The free functions are deprecated and will be removed before 1.0.
Remove InitResponse.data in init. Before 0.9 this was not stored to chain but ignored.
Use cosmwasm_storage::transactional instead of the removed cosmwasm_storage::transactional_deps.
Replace cosmwasm_std::Never with cosmwasm_std::Empty.

Integration tests:

Replace cosmwasm_vm::ReadonlyStorage with cosmwasm_vm::Storage, which now contains all backend storage methods.
Storage getters (and iterators) now return a result of (Option<Vec<u8>>, u64), where the first component is the element and the second one is the gas cost. Thus in a few places .0 must be added to access the element.

0.7.2 -> 0.8

Update wasm code

Cargo.toml dependencies:

Update to schemars = "0.7"
Replace cosmwasm = "0.7" with cosmwasm-std = "0.8"
Replace cosmwasm-vm = "0.7" with cosmwasm-vm = "0.8"
Replace cw-storage = "0.2" with cosmwasm-storage = "0.8"
Remove explicit snafu dependency. cosmwasm_std still uses it internally but doesn't expose snafu specifics anymore. See more details on errors below.

(Note: until release of 0.8, you need to use git references for all cosmwasm_* packages)

Cargo.toml features:

Replace "cosmwasm/backtraces" with "cosmwasm-std/backtraces"

Imports:

Replace all use cosmwasm::X::Y with use cosmwasm_std::Y, except for mock
Replace all use cosmwasm::mock::Y with use cosmwasm_std::testing::Y. This should only be used in test code.
Replace cw_storage:X with cosmwasm_storage::X
Replace cosmwasm_std::Response with cosmwasm_std::HandleResponse and cosmwasm_std::InitResponse (different type for each call)

src/lib.rs:

This has been re-written, but is generic boilerplate and should be (almost) the same in all contracts:

copy the new version from contracts/queue
Add pub mod XYZ directives for any modules you use besides contract

Contract Code:

Add query to extern:
- Before: my_func<S: Storage, A: Api>(deps: &Extern<S, A>, ...
- After: my_func<S: Storage, A: Api, Q: Querier>(deps: &Extern<S, A, Q>, ...
- Remember to add use cosmwasm_std::Querier;
query now returns StdResult<Binary> instead of Result<Vec<u8>>
- You can also replace to_vec(...) with to_binary(...)
No .context(...) is required after from_slice and to_vec, they return proper cosmwasm_std::Error variants on errors.
env.message.signer becomes env.message.sender.

If you used env.contract.balance, you must now use the querier. The following code block should work:

// before (in env)
let foo = env.contract.balance;

// after (query my balance)
let contract_addr = deps.api.human_address(&env.contract.address)?;
let balance = deps.querier.query_all_balances(&contract_addr)?;
let foo = balance.amount;

Update the CosmosMsg enums used:
- CosmosMsg::Send{} => CosmosMsg::Bank(BankMsg::Send{})
- CosmosMsg::Opaque{ data } => CosmosMsg::Native{ msg }
- CosmosMsg::Contract => CosmosMsg::Wasm(WasmMsg::Execute{})
Complete overhaul of cosmwasm::Error into cosmwasm_std::StdError:
- Auto generated snafu error constructor structs like NotFound/ParseErr/… have been privatized in favour of error generation helpers like not_found/parse_err/…
- All error generator functions now return errors instead of results, such that e.g. return unauthorized(); becomes return Err(unauthorized());
- Error cases don't contain source fields anymore. Instead source errors are converted to standard types like String. For this reason, both snafu::ResultExt and snafu::OptionExt cannot be used anymore. An error wrapper now looks like .map_err(invalid_base64) and an Option::None to error mapping looks like .ok_or_else(|| not_found("State")).
- Backtraces became optional. Use RUST_BACKTRACE=1 to enable them for unit tests.
- Utf8Err/Utf8StringErr merged into StdError::InvalidUtf8
- Base64Err renamed into StdError::InvalidBase64
- ContractErr/DynContractErr merged into StdError::GenericErr, thus both contract_err and dyn_contract_err must be replaced with generic_err.
- The unused ValidationErr was removed

At this point cargo wasm should pass.

Update test code

Both:

Update all imports from cosmwasm::mock::* to cosmwasm_std::testing::*
Use from_binary not from_slice on all query responses (update imports)
- from_slice(res.as_slice()) -> from_binary(&res)
Replace coin("123", "FOO") with coins(123, "FOO"). We renamed it to coins to be more explicit that it returns Vec<Coin>, and now accept a u128 as the first argument for better type-safety. coin is now an alias to Coin::new and returns one Coin.
Remove the 4th argument (contract balance) from all calls to mock_env, this is no longer stored in the environment.

dependencies was renamed to mock_dependencies. mock_dependencies and mock_instance take a 2nd argument to set the contract balance (visible for the querier). If you need to set more balances, use mock_XX_with_balances. The follow code block explains:

// before: balance as last arg in mock_env
let mut deps = dependencies(20);
let env = mock_env(&deps.api, "creator", &coins(15, "earth"), &coins(1015, "earth"));

// after: balance as last arg in mock_dependencies
let mut deps = mock_dependencies(20, &coins(1015, "earth"));
let env = mock_env(&deps.api, "creator", &coins(15, "earth"));

Unit Tests:

Replace dependencies with mock_dependencies

Integration Tests:

We no longer check errors as strings but have rich types:
- Before: match err { ContractResult::Err(msg) => assert_eq!(msg, "Unauthorized"), ... }
- After: match err { Err(StdError::Unauthorized{ .. }) => {}, ... }
Remove all imports / use of ContractResult
You must specify CosmosMsg::Native type when calling cosmwasm_vm::testing::{handle, init}. You will want to use cosmwasm_std::{HandleResult, InitResult} or use cosmwasm_std::{HandleResponse, InitResponse}. If you don't use custom native types, simply update calls as follows:
- let res = init(...) => let res: InitResult = init(...)
- let res = init(...).unwrap() => let res: InitResponse = init(...).unwrap()
- let res = handle(...) => let res: HandleResult = handle(...)
- let res = handle(...).unwrap() => let res: HandleResponse = handle(...).unwrap()

Update schema code

All helper functions have been moved into a new cosmwasm-schema package.

Add cosmwasm-schema = "0.8" to [dev-dependencies] in Cargo.toml
Remove serde_json [dev-dependency] if there, as cosmwasm-schema will handle JSON output internally.
Update examples/schema.rs to look more like queue, but replacing all the imports and type names with those you currently have.
Regenerate schemas with cargo schema

Polishing

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cargo fmt
cargo clippy

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MIGRATING.md

MIGRATING.md

Migrating Contracts

1.0.0-beta -> 1.0.0 (unreleased)

0.16 -> 1.0.0-beta

Integration tests

0.15 -> 0.16

0.14 -> 0.15

0.13 -> 0.14

0.12 -> 0.13

0.11 -> 0.12

0.10 -> 0.11

0.9 -> 0.10

0.8 -> 0.9

0.7.2 -> 0.8

Update wasm code

Update test code

Update schema code

Polishing

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MIGRATING.md

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Migrating Contracts

1.0.0-beta -> 1.0.0 (unreleased)

0.16 -> 1.0.0-beta

Integration tests

0.15 -> 0.16

0.14 -> 0.15

0.13 -> 0.14

0.12 -> 0.13

0.11 -> 0.12

0.10 -> 0.11

0.9 -> 0.10

0.8 -> 0.9

0.7.2 -> 0.8

Update wasm code

Update test code

Update schema code

Polishing