introduce common.copy() for deep copy

Author: ryanio

packages/client/lib/config.ts

@@ -194,8 +194,8 @@ export class Config {
     // TODO: map chainParams (and lib/util.parseParams) to new Common format
     const common =
       options.common ?? new Common({ chain: Config.CHAIN_DEFAULT, hardfork: 'chainstart' })
-    this.chainCommon = Object.assign(Object.create(Object.getPrototypeOf(common)), common)
-    this.execCommon = Object.assign(Object.create(Object.getPrototypeOf(common)), common)
+    this.chainCommon = common.copy()
+    this.execCommon = common.copy()
 
     this.discDns = this.getDnsDiscovery(options.discDns)
     this.discV4 = this.getV4Discovery(options.discV4)

packages/common/src/index.ts

@@ -742,4 +742,11 @@ export default class Common extends EventEmitter {
   consensusConfig(): any {
     return (<any>this._chainParams)['consensus'][this.consensusAlgorithm()]
   }
+
+  /**
+   * Returns a deep copy of this common instance.
+   */
+  copy(): Common {
+    return Object.assign(Object.create(Object.getPrototypeOf(this)), this)
+  }
 }

packages/tx/src/baseTransaction.ts

@@ -46,10 +46,7 @@ export abstract class BaseTransaction<TransactionObject> {
 
     this._validateExceedsMaxInteger(validateCannotExceedMaxInteger)
 
-    this.common =
-      (txOptions.common &&
-        Object.assign(Object.create(Object.getPrototypeOf(txOptions.common)), txOptions.common)) ??
-      new Common({ chain: 'mainnet' })
+    this.common = txOptions.common?.copy() ?? new Common({ chain: 'mainnet' })
   }
 
   /**