Fix a bug in assembleTransaction (#57)

* Fix a bug in assembleTransaction

* Add regression test

* Add basic test for non-invokeHostFunction ops

src/transaction.ts

@@ -51,11 +51,11 @@ export function assembleTransaction(
       if (!sim) {
         throw new Error("missing simulated operation");
       }
-      let footprint = sim.footprint;
+      let footprint = sim.footprint ?? rawOp.footprint;
       if (!(footprint instanceof xdr.LedgerFootprint)) {
         footprint = xdr.LedgerFootprint.fromXDR(footprint.toString(), "base64");
       }
-      const auth = sim.auth.map((a) =>
+      const auth = (sim.auth ?? rawOp.auth).map((a) =>
         a instanceof xdr.ContractAuth
           ? a
           : xdr.ContractAuth.fromXDR(a.toString(), "base64"),

test/unit/transaction_test.js

@@ -78,5 +78,37 @@ describe("assembleTransaction", () => {
 
       expect(result.operations[0].auth.length).to.equal(1);
     });
+
+    it("throws for non-invokehost-fn ops", () => {
+      const txn = new SorobanClient.TransactionBuilder(source, {
+        fee: 100,
+        networkPassphrase,
+        v1: true,
+      })
+        .addOperation(
+          SorobanClient.Operation.changeTrust({
+            asset: SorobanClient.Asset.native(),
+          }),
+        )
+        .setTimeout(SorobanClient.TimeoutInfinite)
+        .build();
+
+      try {
+        SorobanClient.assembleTransaction(txn, networkPassphrase, [null]);
+        expect.fail();
+      } catch (err) {
+        expect(err.toString()).to.equal("Error: Unsupported operation type");
+      }
+    });
+
+    it("handles transactions with no auth or footprint", () => {
+      const txn = emptyTransaction();
+
+      const result = SorobanClient.assembleTransaction(txn, networkPassphrase, [
+        {},
+      ]);
+
+      expect(result.operations[0].auth.length).to.equal(0);
+    });
   });
 });