From 5a842e440f0ec565eba38aec4c1c953a775557ea Mon Sep 17 00:00:00 2001
From: Dan <danjm.com@gmail.com>
Date: Fri, 25 May 2018 11:07:16 -0230
Subject: [PATCH] Gas estimation uses block gas limit as fallback if
 query.estimateGas returns an expected error.

---
 ui/app/components/send_/send.utils.js         | 15 +++++++---
 .../components/send_/tests/send-utils.test.js | 29 ++++++++++++++++++-
 2 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/ui/app/components/send_/send.utils.js b/ui/app/components/send_/send.utils.js
index 750411908..9b8f1d118 100644
--- a/ui/app/components/send_/send.utils.js
+++ b/ui/app/components/send_/send.utils.js
@@ -193,14 +193,21 @@ async function estimateGas ({ selectedAddress, selectedToken, data, blockGasLimi
     roundDown: '0',
     toNumericBase: 'hex',
   }))
-
   // run tx
   return new Promise((resolve, reject) => {
-    estimateGasMethod(paramsForGasEstimate, (err, estimatedGas) => {
+    return estimateGasMethod(paramsForGasEstimate, (err, estimatedGas) => {
       if (err) {
-        reject(err)
+        const simulationFailed = (
+          err.message.includes('Transaction execution error.') ||
+          err.message.includes('gas required exceeds allowance or always failing transaction')
+        )
+        if (simulationFailed) {
+          return resolve(paramsForGasEstimate.gas)
+        } else {
+          return reject(err)
+        }
       }
-      resolve(estimatedGas.toString(16))
+      return resolve(estimatedGas.toString(16))
     })
   })
 }
diff --git a/ui/app/components/send_/tests/send-utils.test.js b/ui/app/components/send_/tests/send-utils.test.js
index 3c772ed47..4801d4a09 100644
--- a/ui/app/components/send_/tests/send-utils.test.js
+++ b/ui/app/components/send_/tests/send-utils.test.js
@@ -241,7 +241,10 @@ describe('send utils', () => {
       selectedAddress: 'mockAddress',
       to: '0xisContract',
       estimateGasMethod: sinon.stub().callsFake(
-        (data, cb) => cb(null, { toString: (n) => `mockToString:${n}` })
+        (data, cb) => cb(
+          data.to.match(/willFailBecauseOf:/) ? { message: data.to.match(/\:(.+)$/)[1] } : null,
+          { toString: (n) => `mockToString:${n}` }
+        )
       ),
     }
     const baseExpectedCall = {
@@ -298,6 +301,30 @@ describe('send utils', () => {
       const result = await estimateGas(Object.assign({}, baseMockParams, { to: '0x123' }))
       assert.equal(result, SIMPLE_GAS_COST)
     })
+
+    it(`should return the adjusted blockGasLimit if it fails with a 'Transaction execution error.'`, async () => {
+      const result = await estimateGas(Object.assign({}, baseMockParams, {
+        to: 'isContract willFailBecauseOf:Transaction execution error.',
+      }))
+      assert.equal(result, '0x64x0.95')
+    })
+
+    it(`should return the adjusted blockGasLimit if it fails with a 'gas required exceeds allowance or always failing transaction.'`, async () => {
+      const result = await estimateGas(Object.assign({}, baseMockParams, {
+        to: 'isContract willFailBecauseOf:gas required exceeds allowance or always failing transaction.',
+      }))
+      assert.equal(result, '0x64x0.95')
+    })
+
+    it(`should reject other errors`, async () => {
+      try {
+        await estimateGas(Object.assign({}, baseMockParams, {
+          to: 'isContract willFailBecauseOf:some other error',
+        }))
+      } catch (err) {
+        assert.deepEqual(err, { message: 'some other error' })
+      }
+    })
   })
 
   describe('estimateGasPriceFromRecentBlocks', () => {