Add errorHelper, cleanup error handling when blocks are out of range

lib/database/leveluparrayadapter.js

@@ -1,4 +1,5 @@
 var Sublevel = require("level-sublevel");
+const { LevelUpOutOfRangeError, BlockOutOfRangeError } = require("../utils/errorhelper");
 
 // Level up adapter that looks like an array. Doesn't support inserts.
 
@@ -58,11 +59,11 @@ LevelUpArrayAdapter.prototype.get = function(index, callback) {
       return callback(err);
     }
     if (index >= length) {
-      return callback(
-        new Error(
-          "LevelUpArrayAdapter named '" + self.name + "' index out of range: index " + index + "; length: " + length
-        )
-      );
+      // index out of range
+      let RangeError = self.name === "blocks"
+        ? new BlockOutOfRangeError(index, length)
+        : new LevelUpOutOfRangeError(self.name, index, length);
+      return callback(RangeError);
     }
     self._get(index, callback);
   });

lib/statemanager.js

@@ -12,6 +12,7 @@ var ForkedBlockchain = require("./utils/forkedblockchain.js");
 var Web3 = require("web3");
 var sigUtil = require("eth-sig-util");
 var _ = require("lodash");
+const { BlockOutOfRangeError } = require("./utils/errorhelper");
 
 var to = require("./utils/to");
 var random = require("./utils/random");
@@ -627,7 +628,7 @@ StateManager.prototype.processCall = function(from, rawTx, blockNumber, callback
 
     self.blockchain.processCall(tx, blockNumber, function(err, results) {
       if (err) {
-        if (err.message.indexOf("LevelUpArrayAdapter named 'blocks' index out of range: index") >= 0) {
+        if (err instanceof BlockOutOfRangeError) {
           // block doesn't exist
           return callback(null, null);
         }

lib/subproviders/geth_api_double.js

@@ -5,6 +5,7 @@ var to = require("../utils/to");
 var txhelper = require("../utils/txhelper");
 var blockHelper = require("../utils/block_helper");
 var pkg = require("../../package.json");
+const { BlockOutOfRangeError } = require("../utils/errorhelper");
 
 var Subprovider = require("web3-provider-engine/subproviders/subprovider.js");
 
@@ -188,7 +189,7 @@ GethApiDouble.prototype.eth_getBlockByHash = function(txHash, includeFullTransac
 GethApiDouble.prototype.eth_getBlockTransactionCountByNumber = function(blockNumber, callback) {
   this.state.blockchain.getBlock(blockNumber, function(err, block) {
     if (err) {
-      if (err.message.indexOf("LevelUpArrayAdapter named 'blocks' index out of range: index") >= 0) {
+      if (err instanceof BlockOutOfRangeError) {
         // block doesn't exist
         return callback(null, 0);
       }

lib/utils/errorhelper.js

@@ -0,0 +1,20 @@
+class LevelUpOutOfRangeError extends Error {
+  constructor(type, index, len) {
+    const message = "LevelUpArrayAdapter named '" + type + "' index out of range: index " + index + "; length: " + len;
+    super(message);
+    this.message = message;
+    this.name = `${this.constructor.name}:${type}`;
+    this.type = type;
+  }
+}
+
+class BlockOutOfRangeError extends LevelUpOutOfRangeError {
+  constructor(index, len) {
+    super("blocks", index, len);
+  }
+}
+
+module.exports = {
+  LevelUpOutOfRangeError,
+  BlockOutOfRangeError
+};