VM: add selectHardforkByBlockNumber option (#966)

* vm: add selectHardforkByBlockNumber option

packages/vm/lib/index.ts

@@ -89,6 +89,13 @@ export interface VMOpts {
    * Default: `false` [ONLY set to `true` during debugging]
    */
   allowUnlimitedContractSize?: boolean
+
+  /**
+   * Select hardfork based upon block number. This automatically switches to the right hard fork based upon the block number.
+   *
+   * Default: `true`
+   */
+  selectHardforkByBlockNumber?: boolean
 }
 
 /**
@@ -113,6 +120,7 @@ export default class VM extends AsyncEventEmitter {
   protected _isInitialized: boolean = false
   protected readonly _allowUnlimitedContractSize: boolean
   protected _opcodes: OpcodeList
+  protected readonly _selectHardforkByBlockNumber: boolean
 
   /**
    * Cached emit() function, not for public usage
@@ -203,6 +211,8 @@ export default class VM extends AsyncEventEmitter {
 
     this._allowUnlimitedContractSize = opts.allowUnlimitedContractSize || false
 
+    this._selectHardforkByBlockNumber = opts.selectHardforkByBlockNumber ?? true
+
     if (this._common.eips().includes(2537)) {
       if (IS_BROWSER) {
         throw new Error('EIP-2537 is currently not supported in browsers')

packages/vm/lib/runBlock.ts

@@ -122,6 +122,14 @@ export default async function runBlock(this: VM, opts: RunBlockOpts): Promise<Ru
    */
   await this._emit('beforeBlock', block)
 
+  if (this._selectHardforkByBlockNumber) {
+    const currentHf = this._common.hardfork()
+    this._common.setHardforkByBlockNumber(block.header.number.toNumber())
+    if (this._common.hardfork() != currentHf) {
+      this._updateOpcodes()
+    }
+  }
+
   // Set state root if provided
   if (root) {
     await state.setStateRoot(root)

packages/vm/tests/BlockchainTestsRunner.ts

@@ -71,6 +71,7 @@ export default async function runBlockchainTest(options: any, testData: any, t:
     state,
     blockchain,
     common,
+    selectHardforkByBlockNumber: false,
   })
 
   // set up pre-state

packages/vm/tests/api/runBlock.spec.ts

@@ -7,6 +7,7 @@ import { DefaultStateManager } from '../../lib/state'
 import runBlock from '../../lib/runBlock'
 import { setupPreConditions, getDAOCommon } from '../util'
 import { setupVM, createAccount } from './utils'
+import VM from '../../lib/index'
 
 const testData = require('./testdata.json')
 
@@ -110,6 +111,67 @@ tape('should fail when tx gas limit higher than block gas limit', async (t) => {
   t.end()
 })
 
+tape('should correctly use the selectHardforkByBlockNumber option', async (t) => {
+  const common1 = new Common({
+    chain: 'mainnet',
+    hardfork: 'chainstart',
+  })
+
+  // Have to use an unique common, otherwise the HF will be set to muirGlacier and then will not change back to chainstart.
+  const common2 = new Common({
+    chain: 'mainnet',
+    hardfork: 'chainstart',
+  })
+
+  const privateKey = Buffer.from(
+    'e331b6d69882b4cb4ea581d88e0b604039a3de5967688d3dcffdd2270c0fd109',
+    'hex'
+  )
+
+  function getBlock(common: Common): Block {
+    return Block.fromBlockData(
+      {
+        header: {
+          number: new BN(10000000),
+        },
+        transactions: [
+          Transaction.fromTxData(
+            {
+              data: '0x600154', // PUSH 01 SLOAD
+              gasLimit: new BN(100000),
+            },
+            { common }
+          ).sign(privateKey),
+        ],
+      },
+      { common }
+    )
+  }
+
+  const vm = new VM({ common: common1 })
+  const vm_noSelect = new VM({ common: common2, selectHardforkByBlockNumber: false })
+
+  const txResultMuirGlacier = await vm.runBlock({
+    block: getBlock(common1),
+    skipBlockValidation: true,
+    generate: true,
+  })
+  const txResultChainstart = await vm_noSelect.runBlock({
+    block: getBlock(common2),
+    skipBlockValidation: true,
+    generate: true,
+  })
+  t.ok(
+    txResultChainstart.results[0].gasUsed.toNumber() == 21000 + 68 * 3 + 3 + 50,
+    'tx charged right gas on chainstart hard fork'
+  )
+  t.ok(
+    txResultMuirGlacier.results[0].gasUsed.toNumber() == 21000 + 32000 + 16 * 3 + 3 + 800,
+    'tx charged right gas on muir glacier hard fork'
+  )
+  t.end()
+})
+
 tape('should run valid block', async (t) => {
   const vm = setupVM()
   const suite = setup(vm)

packages/vm/tests/api/utils.ts

@@ -22,5 +22,8 @@ export function setupVM(opts: VMOpts & { genesisBlock?: Block } = {}) {
       genesisBlock,
     })
   }
-  return new VM(opts)
+  return new VM({
+    selectHardforkByBlockNumber: false,
+    ...opts,
+  })
 }