Allow transactions with 0-gwei gas price (#4073)

* Allow transactions with 0-gwei gas price
* Add tests to verify tx with 0 gas fee
* Conditionally use CurrencyInput in CurrencyDisplay

3 files changed, 11 insertions, 12 deletions

diff --git a/ui/app/components/customize-gas-modal/index.js b/ui/app/components/customize-gas-modal/index.js
index 4c693d1c3..1ff8eea87 100644
--- a/ui/app/components/customize-gas-modal/index.js
+++ b/ui/app/components/customize-gas-modal/index.js
@@ -280,8 +280,7 @@ CustomizeGasModal.prototype.render = function () {
         h(GasModalCard, {
           value: convertedGasPrice,
           min: forceGasMin || MIN_GAS_PRICE_GWEI,
-          // max: 1000,
-          step: multiplyCurrencies(MIN_GAS_PRICE_GWEI, 10),
+          step: 1,
           onChange: value => this.convertAndSetGasPrice(value),
           title: this.context.t('gasPrice'),
           copy: this.context.t('gasPriceCalculation'),
@@ -290,7 +289,6 @@ CustomizeGasModal.prototype.render = function () {
         h(GasModalCard, {
           value: convertedGasLimit,
           min: 1,
-          // max: 100000,
           step: 1,
           onChange: value => this.convertAndSetGasLimit(value),
           title: this.context.t('gasLimit'),
diff --git a/ui/app/components/send/currency-display.js b/ui/app/components/send/currency-display.js
index a7bd5d7ea..90fb2b66c 100644
--- a/ui/app/components/send/currency-display.js
+++ b/ui/app/components/send/currency-display.js
@@ -89,7 +89,6 @@ CurrencyDisplay.prototype.render = function () {
   } = this.props
 
   const valueToRender = this.getValueToRender()
-
   const convertedValueToRender = this.getConvertedValueToRender(valueToRender)
 
   return h('div', {
@@ -97,22 +96,24 @@ CurrencyDisplay.prototype.render = function () {
     style: {
       borderColor: inError ? 'red' : null,
     },
-    onClick: () => this.currencyInput.focus(),
+    onClick: () => this.currencyInput && this.currencyInput.focus(),
   }, [
 
     h('div.currency-display__primary-row', [
 
       h('div.currency-display__input-wrapper', [
 
-        h(CurrencyInput, {
+        h(readOnly ? 'input' : CurrencyInput, {
           className: primaryBalanceClassName,
           value: `${valueToRender}`,
           placeholder: '0',
           readOnly,
-          onInputChange: newValue => {
-            handleChange(this.getAmount(newValue))
-          },
-          inputRef: input => { this.currencyInput = input },
+          ...(!readOnly ? {
+            onInputChange: newValue => {
+              handleChange(this.getAmount(newValue))
+            },
+            inputRef: input => { this.currencyInput = input },
+          } : {}),
         }),
 
         h('span.currency-display__currency-symbol', primaryCurrency),
diff --git a/ui/app/components/send/send-constants.js b/ui/app/components/send/send-constants.js
index b3ee0899a..5d89c74aa 100644
--- a/ui/app/components/send/send-constants.js
+++ b/ui/app/components/send/send-constants.js
@@ -1,8 +1,8 @@
 const ethUtil = require('ethereumjs-util')
 const { conversionUtil, multiplyCurrencies } = require('../../conversion-util')
 
-const MIN_GAS_PRICE_HEX = (100000000).toString(16)
-const MIN_GAS_PRICE_DEC = '100000000'
+const MIN_GAS_PRICE_DEC = '0'
+const MIN_GAS_PRICE_HEX = (parseInt(MIN_GAS_PRICE_DEC)).toString(16)
 const MIN_GAS_LIMIT_DEC = '21000'
 const MIN_GAS_LIMIT_HEX = (parseInt(MIN_GAS_LIMIT_DEC)).toString(16)