Add QueryResponseType trait

CHANGELOG.md

@@ -23,7 +23,8 @@ and this project adheres to
 - cosmwasm-std: Upgrade `serde-json-wasm` dependency to 0.5.0 which adds map
   support to `to_vec`/`to_binary` and friends.
 - cosmwasm-std: Implement `AsRef<[u8]>` for `Binary` and `HexBinary` ([#1550]).
-- cosmwasm-std: Add constructor `SupplyResponse::new` ([#1552]).
+- cosmwasm-std: Allow constructing `SupplyResponse` via a `Default`
+  implementation ([#1552]).
 
 [#1436]: https://github.com/CosmWasm/cosmwasm/issues/1436
 [#1437]: https://github.com/CosmWasm/cosmwasm/issues/1437

packages/std/src/query/bank.rs

@@ -3,6 +3,8 @@ use serde::{Deserialize, Serialize};
 
 use crate::Coin;
 
+use super::query_response::QueryResponseType;
+
 #[non_exhaustive]
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
@@ -22,7 +24,7 @@ pub enum BankQuery {
 }
 
 #[cfg(feature = "cosmwasm_1_1")]
-#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
+#[derive(Serialize, Deserialize, Clone, Debug, Default, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 #[non_exhaustive]
 pub struct SupplyResponse {
@@ -32,28 +34,23 @@ pub struct SupplyResponse {
 }
 
 #[cfg(feature = "cosmwasm_1_1")]
-impl SupplyResponse {
-    /// Constructor for testing frameworks such as cw-multi-test.
-    /// This is required because query response types should be #[non_exhaustive].
-    /// As a contract developer you should not need this constructor since
-    /// query responses are constructed for you via deserialization.
-    #[doc(hidden)]
-    pub fn new(amount: Coin) -> Self {
-        Self { amount }
-    }
-}
+impl QueryResponseType for SupplyResponse {}
 
-#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
+#[derive(Serialize, Deserialize, Clone, Debug, Default, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 pub struct BalanceResponse {
     /// Always returns a Coin with the requested denom.
     /// This may be of 0 amount if no such funds.
     pub amount: Coin,
 }
 
-#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
+impl QueryResponseType for BalanceResponse {}
+
+#[derive(Serialize, Deserialize, Clone, Debug, Default, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
 pub struct AllBalanceResponse {
     /// Returns all non-zero coins held by this account.
     pub amount: Vec<Coin>,
 }
+
+impl QueryResponseType for AllBalanceResponse {}

packages/std/src/query/mod.rs

@@ -7,6 +7,7 @@ use crate::Empty;
 
 mod bank;
 mod ibc;
+mod query_response;
 mod staking;
 mod wasm;
 

packages/std/src/query/query_response.rs

@@ -0,0 +1,16 @@
+use serde::de::DeserializeOwned;
+
+/// A marker trait for query response types.
+///
+/// Those types have in common that they should be `#[non_exhaustive]` in order
+/// to allow adding fields in a backwards compatible way. In contracts they are
+/// only constructed through deserialization. We want to make it hard for
+/// contract developers to construct those types themselves as this is most likely
+/// not what they should do.
+///
+/// In hosts they are constructed as follows:
+/// - wasmvm: Go types with the same JSON layout
+/// - multi-test/cw-sdk: create a default instance and mutate the fields
+///
+/// This trait is crate-internal and can change any time.
+pub(crate) trait QueryResponseType: Default + DeserializeOwned {}

packages/std/src/query/wasm.rs

@@ -3,6 +3,8 @@ use serde::{Deserialize, Serialize};
 
 use crate::Binary;
 
+use super::query_response::QueryResponseType;
+
 #[non_exhaustive]
 #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
 #[serde(rename_all = "snake_case")]
@@ -27,7 +29,7 @@ pub enum WasmQuery {
 }
 
 #[non_exhaustive]
-#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, JsonSchema)]
+#[derive(Serialize, Deserialize, Clone, Default, Debug, PartialEq, Eq, JsonSchema)]
 pub struct ContractInfoResponse {
     pub code_id: u64,
     /// address that instantiated this contract
@@ -40,6 +42,8 @@ pub struct ContractInfoResponse {
     pub ibc_port: Option<String>,
 }
 
+impl QueryResponseType for ContractInfoResponse {}
+
 impl ContractInfoResponse {
     /// Constructor for testing frameworks such as cw-multi-test.
     /// This is required because query response types should be #[non_exhaustive].