Make schema an optional pointer so that it's omitted when empty

Makefile

@@ -11,7 +11,7 @@ endif
 # Both cases should fallback to default of getting the version from git tag.
 ifeq ($(strip $(REPOSITORY_VERSION)),)
 	override REPOSITORY_VERSION = "$(shell git describe --tags --always --abbrev=0 --match='v[0-9]*.[0-9]*.[0-9]*' 2> /dev/null | sed 's/^.//')"
-endif  
+endif
 REPOSITORY_BRANCH := "$(shell git rev-parse --abbrev-ref HEAD)"
 BUILD_TIMESTAMP ?= $(shell date '+%Y-%m-%dT%H:%M:%S')
 GOLDFLAGS :=	-X 'github.com/stellar/soroban-tools/cmd/soroban-rpc/internal/config.Version=${REPOSITORY_VERSION}' \
@@ -62,12 +62,12 @@ build-libpreflight: Cargo.lock
 	cd cmd/soroban-rpc/lib/preflight && cargo build --target $(CARGO_BUILD_TARGET) --profile release-with-panic-unwind
 
 build-test-wasms: Cargo.lock
-	cargo build --package 'test_*' --profile test-wasms --target wasm32-unknown-unknown
+	cargo build --package 'test_*' --profile test-wasms --target wasm32-unknown-unknown --jobs 4
 
 build-test: build-test-wasms install_rust
 
 test: build-test
-	cargo test 
+	cargo test
 
 e2e-test:
 	cargo test --test it -- --ignored
@@ -88,7 +88,7 @@ clean:
 publish:
 	cargo workspaces publish --all --force '*' --from-git --yes
 
-# the build-soroban-rpc build target is an optimized build target used by 
+# the build-soroban-rpc build target is an optimized build target used by
 # https://github.com/stellar/pipelines/stellar-horizon/Jenkinsfile-soroban-rpc-package-builder
 # as part of the package building.
 build-soroban-rpc: build-libpreflight
@@ -101,7 +101,7 @@ lint:
 	golangci-lint run ./...
 
 typescript-bindings-fixtures: build-test-wasms
-	cargo run -- contract bindings typescript \
+	cargo run --jobs 4 -- contract bindings typescript \
 					--wasm ./target/wasm32-unknown-unknown/test-wasms/test_custom_types.wasm \
 					--contract-id CBYMYMSDF6FBDNCFJCRC7KMO4REYFPOH2U4N7FXI3GJO6YXNCQ43CDSK \
 					--network futurenet \

cmd/soroban-rpc/internal/methods/simulate_transaction.go

@@ -42,7 +42,7 @@ type SimulateTransactionResponse struct {
 	Events          []string                     `json:"events,omitempty"`          // DiagnosticEvent XDR in base64
 	Results         []SimulateHostFunctionResult `json:"results,omitempty"`         // an array of the individual host function call results
 	Cost            SimulateTransactionCost      `json:"cost,omitempty"`            // the effective cpu and memory cost of the invoked transaction execution.
-	RestorePreamble RestorePreamble              `json:"restorePreamble,omitempty"` // If present, it indicates that a prior RestoreFootprint is required
+	RestorePreamble *RestorePreamble             `json:"restorePreamble,omitempty"` // If present, it indicates that a prior RestoreFootprint is required
 	LatestLedger    int64                        `json:"latestLedger,string"`
 }
 
@@ -136,9 +136,9 @@ func NewSimulateTransactionHandler(logger *log.Entry, ledgerEntryReader db.Ledge
 				Auth: base64EncodeSlice(result.Auth),
 			})
 		}
-		restorePreable := RestorePreamble{}
+		var restorePreamble *RestorePreamble = nil
 		if len(result.PreRestoreTransactionData) != 0 {
-			restorePreable = RestorePreamble{
+			restorePreamble = &RestorePreamble{
 				TransactionData: base64.StdEncoding.EncodeToString(result.PreRestoreTransactionData),
 				MinResourceFee:  result.PreRestoreMinFee,
 			}
@@ -155,7 +155,7 @@ func NewSimulateTransactionHandler(logger *log.Entry, ledgerEntryReader db.Ledge
 				MemoryBytes:     result.MemoryBytes,
 			},
 			LatestLedger:    int64(latestLedger),
-			RestorePreamble: restorePreable,
+			RestorePreamble: restorePreamble,
 		}
 	})
 }

cmd/soroban-rpc/internal/test/simulate_transaction_test.go

@@ -184,7 +184,7 @@ func preflightTransactionParamsLocally(t *testing.T, params txnbuild.Transaction
 func preflightTransactionParams(t *testing.T, client *jrpc2.Client, params txnbuild.TransactionParams) txnbuild.TransactionParams {
 	response := simulateTransactionFromTxParams(t, client, params)
 	// The preamble should be zero except for the special restore case
-	assert.Zero(t, response.RestorePreamble)
+	assert.Nil(t, response.RestorePreamble)
 	return preflightTransactionParamsLocally(t, params, response)
 }
 
@@ -858,6 +858,7 @@ func TestSimulateTransactionBumpAndRestoreFootprint(t *testing.T) {
 	waitForExpiration()
 
 	simulationResult := simulateTransactionFromTxParams(t, client, invokeIncPresistentEntryParams)
+	require.NotNil(t, simulationResult.RestorePreamble)
 	assert.NotZero(t, simulationResult.RestorePreamble)
 
 	params = preflightTransactionParamsLocally(t,