fix: price requests for zero should get zero as an answer (#2762)

fixes #2760
Agoric · Mar 30, 2021 · 11285e7 · 11285e7
1 parent 6e779bf
commit 11285e7
Show file tree

Hide file tree

Showing 4 changed files with 107 additions and 0 deletions.
diff --git a/packages/zoe/src/contracts/autoswap.js b/packages/zoe/src/contracts/autoswap.js
@@ -343,6 +343,9 @@ const start = async zcf => {
     const inputReserve = getPoolAmount(amountIn.brand).value;
     const outputReserve = getPoolAmount(brandOut).value;
     assert(isNatValue(amountIn.value));
+    if (amountMath.isEmpty(amountIn)) {
+      return amountMath.makeEmpty(brandOut);
+    }
     const outputValue = getInputPrice(
       amountIn.value,
       inputReserve,
@@ -362,6 +365,9 @@ const start = async zcf => {
     const inputReserve = getPoolAmount(brandIn).value;
     const outputReserve = getPoolAmount(amountOut.brand).value;
     assert(isNatValue(amountOut.value));
+    if (amountMath.isEmpty(amountOut)) {
+      return amountMath.makeEmpty(brandIn);
+    }
     const outputValue = getOutputPrice(
       amountOut.value,
       inputReserve,

diff --git a/packages/zoe/src/contracts/multipoolAutoswap/pool.js b/packages/zoe/src/contracts/multipoolAutoswap/pool.js
@@ -103,6 +103,12 @@ export const makeAddPool = (zcf, isSecondary, initPool, centralBrand) => {
           outputBrand,
         );
         assert(isNatValue(inputAmount.value));
+        if (amountMath.isEmpty(inputAmount)) {
+          return {
+            amountOut: amountMath.makeEmpty(outputBrand),
+            amountIn: amountMath.makeEmpty(inputAmount.brand),
+          };
+        }
         const valueOut = getInputPrice(
           inputAmount.value,
           inputReserve,
@@ -126,6 +132,12 @@ export const makeAddPool = (zcf, isSecondary, initPool, centralBrand) => {
           outputAmount.brand,
         );
         assert(isNatValue(outputAmount.value));
+        if (amountMath.isEmpty(outputAmount)) {
+          return {
+            amountOut: amountMath.makeEmpty(outputAmount.brand),
+            amountIn: amountMath.makeEmpty(inputBrand),
+          };
+        }
         const valueIn = getOutputPrice(
           outputAmount.value,
           inputReserve,

diff --git a/packages/zoe/test/unitTests/contracts/test-autoswap.js b/packages/zoe/test/unitTests/contracts/test-autoswap.js
@@ -622,3 +622,62 @@ test('autoSwap jig - swap varying amounts', async t => {
 
   // attempt a trade with bad numbers
 });
+
+test('autoSwap price quote for zero', async t => {
+  const {
+    moolaIssuer,
+    simoleanIssuer,
+    moolaMint,
+    simoleanMint,
+    moola,
+    simoleans,
+    zoe,
+  } = setup();
+  const installation = await installationPFromSource(zoe, autoswap);
+
+  // Setup Alice
+  const aliceMoolaPayment = moolaMint.mintPayment(moola(10));
+  // Let's assume that simoleans are worth 2x as much as moola
+  const aliceSimoleanPayment = simoleanMint.mintPayment(simoleans(5));
+
+  // Alice creates an autoswap instance
+  const issuerKeywordRecord = harden({
+    Central: moolaIssuer,
+    Secondary: simoleanIssuer,
+  });
+  const startRecord = await zoe.startInstance(
+    installation,
+    issuerKeywordRecord,
+  );
+  /** @type {AutoswapPublicFacet} */
+  const publicFacet = startRecord.publicFacet;
+  const liquidityIssuerP = await E(publicFacet).getLiquidityIssuer();
+  const liquidityBrand = await E(liquidityIssuerP).getBrand();
+  const liquidity = value => amountMath.make(value, liquidityBrand);
+
+  // Alice adds liquidity
+  // 10 moola = 5 simoleans at the time of the liquidity adding
+  // aka 2 moola = 1 simolean
+  const aliceProposal = harden({
+    want: { Liquidity: liquidity(10) },
+    give: { Central: moola(10), Secondary: simoleans(5) },
+  });
+  const alicePayments = {
+    Central: aliceMoolaPayment,
+    Secondary: aliceSimoleanPayment,
+  };
+  const aliceInvitation = await publicFacet.makeAddLiquidityInvitation();
+  await zoe.offer(aliceInvitation, aliceProposal, alicePayments);
+
+  const simoleanAmounts = await E(publicFacet).getInputPrice(
+    moola(0),
+    simoleans(0).brand,
+  );
+  t.deepEqual(simoleanAmounts, simoleans(0), `currentPrice`);
+
+  const moolaAmounts = await E(publicFacet).getOutputPrice(
+    simoleans(0),
+    moola(0n).brand,
+  );
+  t.deepEqual(moolaAmounts, moola(0), `price 0`);
+});
diff --git a/packages/zoe/test/unitTests/contracts/test-autoswapPool.js b/packages/zoe/test/unitTests/contracts/test-autoswapPool.js
@@ -190,3 +190,33 @@ test('pool getOutputPrice cenToCen', async t => {
     },
   );
 });
+
+test('pool getPrice zero', async t => {
+  const allocations = { central: 100n, secondary: 100n };
+  const { pool, centralBrand, central, secondary } = await setupPool(
+    allocations,
+  );
+  const valueIn = 0n;
+  const { amountOut, amountIn } = await E(pool).getPriceGivenAvailableInput(
+    secondary(valueIn),
+    centralBrand,
+  );
+  const expected = 0n;
+  t.deepEqual(amountOut, central(expected));
+  t.deepEqual(amountIn, secondary(valueIn));
+});
+
+test('pool getOutputPrice zero', async t => {
+  const poolBalances = { central: 100n, secondary: 100n };
+  const { pool, secondaryBrand, central, secondary } = await setupPool(
+    poolBalances,
+  );
+  const valueOut = 0n;
+  const { amountOut, amountIn } = await E(pool).getPriceGivenRequiredOutput(
+    secondaryBrand,
+    central(valueOut),
+  );
+  const expected = 0n;
+  t.deepEqual(amountOut, central(valueOut));
+  t.deepEqual(amountIn, secondary(expected));
+});