Merge pull request #525 from ethereumjs/pass-hardfork-and-chain

Accept a Common object when constructing the VM and pass it when copying it

lib/index.ts

@@ -45,6 +45,7 @@ export interface VMOpts {
    * Allows unlimited contract sizes while debugging. By setting this to `true`, the check for contract size limit of 24KB (see [EIP-170](https://git.io/vxZkK)) is bypassed
    */
   allowUnlimitedContractSize?: boolean
+  common?: Common
 }
 
 /**
@@ -71,10 +72,21 @@ export default class VM extends AsyncEventEmitter {
 
     this.opts = opts
 
-    const chain = opts.chain ? opts.chain : 'mainnet'
-    const hardfork = opts.hardfork ? opts.hardfork : 'petersburg'
-    const supportedHardforks = ['byzantium', 'constantinople', 'petersburg']
-    this._common = new Common(chain, hardfork, supportedHardforks)
+    if (opts.common) {
+      if (opts.chain || opts.hardfork) {
+        throw new Error(
+          'You can only instantiate the VM class with one of: opts.common, or opts.chain and opts.hardfork',
+        )
+      }
+
+      this._common = opts.common
+    } else {
+      const chain = opts.chain ? opts.chain : 'mainnet'
+      const hardfork = opts.hardfork ? opts.hardfork : 'petersburg'
+      const supportedHardforks = ['byzantium', 'constantinople', 'petersburg']
+
+      this._common = new Common(chain, hardfork, supportedHardforks)
+    }
 
     if (opts.stateManager) {
       this.stateManager = opts.stateManager
@@ -141,6 +153,7 @@ export default class VM extends AsyncEventEmitter {
     return new VM({
       stateManager: this.stateManager.copy(),
       blockchain: this.blockchain,
+      common: this._common,
     })
   }
 

tests/api/index.js

@@ -2,6 +2,7 @@ const promisify = require('util.promisify')
 const tape = require('tape')
 const util = require('ethereumjs-util')
 const Block = require('ethereumjs-block')
+const Common = require('ethereumjs-common').default
 const Trie = require('merkle-patricia-tree/secure')
 const VM = require('../../dist/index').default
 const { setupVM } = require('./utils')
@@ -31,6 +32,25 @@ tape('VM with default blockchain', (t) => {
     st.end()
   })
 
+  t.test('should only accept common or chain and fork', (st) => {
+    const common = new Common('mainnet');
+
+    st.throws(() => new VM({ chain: 'a', common }))
+    st.throws(() => new VM({ hardfork: 'a', common }))
+    st.throws(() => new VM({ chain: 'a', hardfork: 'a', common }))
+
+    st.end()
+  })
+
+  t.test('should accept a common object as option', (st) => {
+    const common = new Common('mainnet')
+
+    const vm = new VM({ common })
+    st.equal(vm._common, common)
+
+    st.end()
+  })
+
   t.test('should only accept valid chain and fork', (st) => {
     let vm = new VM({ chain: 'ropsten', hardfork: 'byzantium' })
     st.equal(vm.stateManager._common.param('gasPrices', 'ecAdd'), 500)
@@ -115,6 +135,18 @@ tape('VM with blockchain', (t) => {
 
     st.end()
   })
+
+  t.test('should pass the correct Common object when copying the VM', st => {
+    const vm = setupVM({ chain: 'goerli', hardfork: 'byzantium' })
+    st.equal(vm._common.chainName(), 'goerli')
+    st.equal(vm._common.hardfork(), 'byzantium')
+
+    const copiedVM = vm.copy()
+    st.equal(copiedVM._common.chainName(), 'goerli')
+    st.equal(copiedVM._common.hardfork(), 'byzantium')
+
+    st.end()
+  })
 })
 
 const runBlockchainP = (vm) => promisify(vm.runBlockchain.bind(vm))()