Fix

x/wasm/keeper/keeper.go

@@ -171,7 +171,13 @@ func (k Keeper) create(ctx context.Context, creator sdk.AccAddress, wasmCode []b
 	}
 
 	gasLeft := k.runtimeGasForContract(sdkCtx)
-	checksum, gasUsed, err := k.wasmVM.StoreCode(wasmCode, gasLeft)
+	var gasUsed uint64
+	if sdkCtx.ExecMode() == sdk.ExecModeSimulate {
+		// only simulate storing the code, no files are written
+		checksum, gasUsed, err = k.wasmVM.SimulateStoreCode(wasmCode, gasLeft)
+	} else {
+		checksum, gasUsed, err = k.wasmVM.StoreCode(wasmCode, gasLeft)
+	}
 	k.consumeRuntimeGas(sdkCtx, gasUsed)
 	if err != nil {
 		return 0, checksum, errorsmod.Wrap(types.ErrCreateFailed, err.Error())

x/wasm/keeper/wasmtesting/mock_engine.go

@@ -24,6 +24,7 @@ var _ types.WasmEngine = &MockWasmEngine{}
 type MockWasmEngine struct {
 	StoreCodeFn              func(codeID wasmvm.WasmCode, gasLimit uint64) (wasmvm.Checksum, uint64, error)
 	StoreCodeUncheckedFn     func(codeID wasmvm.WasmCode) (wasmvm.Checksum, error)
+	SimulateStoreCodeFn      func(codeID wasmvm.WasmCode, gasLimit uint64) (wasmvm.Checksum, uint64, error)
 	AnalyzeCodeFn            func(codeID wasmvm.Checksum) (*wasmvmtypes.AnalysisReport, error)
 	InstantiateFn            func(codeID wasmvm.Checksum, env wasmvmtypes.Env, info wasmvmtypes.MessageInfo, initMsg []byte, store wasmvm.KVStore, goapi wasmvm.GoAPI, querier wasmvm.Querier, gasMeter wasmvm.GasMeter, gasLimit uint64, deserCost wasmvmtypes.UFraction) (*wasmvmtypes.ContractResult, uint64, error)
 	ExecuteFn                func(codeID wasmvm.Checksum, env wasmvmtypes.Env, info wasmvmtypes.MessageInfo, executeMsg []byte, store wasmvm.KVStore, goapi wasmvm.GoAPI, querier wasmvm.Querier, gasMeter wasmvm.GasMeter, gasLimit uint64, deserCost wasmvmtypes.UFraction) (*wasmvmtypes.ContractResult, uint64, error)
@@ -117,6 +118,13 @@ func (m *MockWasmEngine) StoreCodeUnchecked(codeID wasmvm.WasmCode) (wasmvm.Chec
 	return m.StoreCodeUncheckedFn(codeID)
 }
 
+func (m *MockWasmEngine) SimulateStoreCode(codeID wasmvm.WasmCode, gasLimit uint64) (wasmvm.Checksum, uint64, error) {
+	if m.SimulateStoreCodeFn == nil {
+		panic("not supposed to be called!")
+	}
+	return m.SimulateStoreCodeFn(codeID, gasLimit)
+}
+
 func (m *MockWasmEngine) AnalyzeCode(codeID wasmvm.Checksum) (*wasmvmtypes.AnalysisReport, error) {
 	if m.AnalyzeCodeFn == nil {
 		panic("not supposed to be called!")

x/wasm/types/wasmer_engine.go

@@ -30,6 +30,11 @@ type WasmEngine interface {
 	// Use this for adding code that was checked before, particularly in the case of state sync.
 	StoreCodeUnchecked(code wasmvm.WasmCode) (wasmvm.Checksum, error)
 
+	// SimulateStoreCode works like StoreCode, but does not actually store the code.
+	// Instead, it just does all the validation and compilation steps without storing the result on disk.
+	// Returns both the checksum, as well as the gas cost of compilation (in CosmWasm Gas) or an error.
+	SimulateStoreCode(code wasmvm.WasmCode, gasLimit uint64) (wasmvm.Checksum, uint64, error)
+
 	// AnalyzeCode will statically analyze the code.
 	// Currently just reports if it exposes all IBC entry points.
 	AnalyzeCode(checksum wasmvm.Checksum) (*wasmvmtypes.AnalysisReport, error)