fix(rpc): Handle rpc request with empty params

README.md

@@ -67,6 +67,105 @@ DEBUG=devp2p:rlpx,devp2p:eth,-babel [CLIENT_START_COMMAND]
 
 See also this [diagram](./client_diagram.png) with an overview of the client structure together with the initialization and message flow.
 
+## JSON-RPC
+
+**Overview**
+
+You can expose a [JSON-RPC](https://github.com/ethereum/wiki/wiki/JSON-RPC) interface along a client run with:
+
+```shell
+ethereumjs --rpc
+```
+
+To run just the server without syncing:
+
+```shell
+ethereumjs --rpc --maxPeers=0
+```
+
+Currently only a small subset of `RPC` methods are implemented.(*) You can have a look at the 
+[./lib/rpc/modules/](./lib/rpc/modules) source folder or the tracking issue 
+[#17](https://github.com/ethereumjs/ethereumjs-client/issues/17) for an overview.
+
+(*) Side note: implementing RPC methods is actually an extremely thankful task for a first-time
+contribution on the project *hint* *hint*. 😄
+
+**API Examples**
+
+You can use `cURL` to request data from an API endpoint. Here is a simple example for
+[web3_clientVersion](https://github.com/ethereum/wiki/wiki/JSON-RPC#web3_clientversion):
+
+```shell
+curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","id":1,"method":"web3_clientVersion", "params": []}' http://localhost:8545
+```
+
+Note that `"params": []` can also be omitted in this case.
+
+Or - somewhat more convenient and with formatted output - with a tool like [httpie](http://httpie.org/):
+
+```shell
+http POST http://localhost:8545 jsonrpc=2.0 id=1 method=web3_clientVersion params:=[]
+```
+
+Note the `:=` separator for the `params` parameter to 
+[indicate](https://httpie.org/docs#non-string-json-fields) raw `JSON` as an input.
+
+This will give you an output like the following:
+
+```json
+{
+    "id": "1",
+    "jsonrpc": "2.0",
+    "result": "EthereumJS/0.0.5/darwin/node12.15.0"
+}
+```
+
+Here an example for a call on an endpoint with the need for parameters. The following call uses
+the [eth_getBlockByNumer](https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getblockbynumber) endpoint
+to request data for block number 436 (you can use an tool like 
+[RapidTables](https://www.rapidtables.com/convert/number/decimal-to-hex.html) for conversion to `hex`):
+
+
+```shell
+curl -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":["0x1b4", true],"id":1}' http://127.0.0.1:8545
+```
+
+Same with `httpie`:
+
+```shell
+http POST http://localhost:8545 jsonrpc=2.0 id=1 method=eth_getBlockByNumber params:='["0x1b4",true]'
+```
+
+Output:
+
+```json
+{
+    "id": "1",
+    "jsonrpc": "2.0",
+    "result": {
+        "header": {
+            "bloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+            "coinbase": "0xbb7b8287f3f0a933474a79eae42cbca977791171",
+            "difficulty": "0x04ea3f27bc",
+            "extraData": "0x476574682f4c5649562f76312e302e302f6c696e75782f676f312e342e32",
+            "gasLimit": "0x1388",
+            "gasUsed": "0x",
+            "mixHash": "0x4fffe9ae21f1c9e15207b1f472d5bbdd68c9595d461666602f2be20daf5e7843",
+            "nonce": "0x689056015818adbe",
+            "number": "0x01b4",
+            "parentHash": "0xe99e022112df268087ea7eafaf4790497fd21dbeeb6bd7a1721df161a6657a54",
+            "receiptTrie": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+            "stateRoot": "0xddc8b0234c2e0cad087c8b389aa7ef01f7d79b2570bccb77ce48648aa61c904d",
+            "timestamp": "0x55ba467c",
+            "transactionsTrie": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+            "uncleHash": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347"
+        },
+        "transactions": [],
+        "uncleHeaders": []
+    }
+}
+```
+
 ## EXAMPLES
 
 ### Example 1: Light sync
@@ -126,6 +225,8 @@ ethereumjs.run({ network: 'rinkeby', syncmode: 'light', bootnodes: '/ip4/127.0.0
 
 That's it! Now, you should start seeing headers being downloaded to the local storage of your browser. Since IndexDB is being used, even if you close and re-open the browser window, the headers you'll already downloaded will be saved.
 
+![EthereumJS Client Libp2p Browser Syncing](./browser_sync.png?raw=true)
+
 ## Design
 
 **Goals**

lib/rpc/modules/eth.js

@@ -24,6 +24,9 @@ class Eth {
     this.getBlockByHash = middleware(this.getBlockByHash.bind(this), 2,
       [[validators.hex, validators.blockHash], [validators.bool]])
 
+    this.getBlockTransactionCountByHash = middleware(this.getBlockTransactionCountByHash.bind(this), 1,
+      [[validators.hex, validators.blockHash]])
+
     this.protocolVersion = middleware(this.protocolVersion.bind(this), 0, [])
   }
 
@@ -76,6 +79,26 @@ class Eth {
     }
   }
 
+  /**
+   * Returns the transaction count for a block given by the block hash
+   * @param  {Array<string>} [params] An array of one parameter: A block hash
+   * @param  {Function} [cb] A function with an error object as the first argument and an actual value
+   * as the second argument
+   * @return {Promise}
+   */
+  async getBlockTransactionCountByHash (params, cb) {
+    let [blockHash] = params
+
+    try {
+      let block = await this._chain.getBlock(toBuffer(blockHash))
+
+      const json = block.toJSON(true)
+      cb(null, `0x${json.transactions.length.toString(16)}`)
+    } catch (err) {
+      cb(err)
+    }
+  }
+
   /**
    * Returns the current ethereum protocol version
    * @param  {Array<*>} [params] An empty array

lib/rpc/validation.js

@@ -8,7 +8,7 @@ module.exports = {
    * @param {Function[]} validators      array of validator
    */
   middleware (method, requiredParamsCount, validators) {
-    return function (params, cb) {
+    return function (params = [], cb) {
       if (params.length < requiredParamsCount) {
         const err = {
           code: INVALID_PARAMS,

lib/service/ethereumservice.js

@@ -37,6 +37,7 @@ class EthereumService extends Service {
 
     this.flow = new FlowControl(options)
     this.chain = options.chain || new Chain(options)
+    this.common = options.common
     this.minPeers = options.minPeers
     this.interval = options.interval
     this.timeout = options.timeout

lib/service/fastethereumservice.js

@@ -39,6 +39,7 @@ class FastEthereumService extends EthereumService {
       logger: this.logger,
       pool: this.pool,
       chain: this.chain,
+      common: this.common,
       minPeers: this.minPeers,
       interval: this.interval
     })

lib/service/lightethereumservice.js

@@ -31,6 +31,7 @@ class LightEthereumService extends EthereumService {
       logger: this.logger,
       pool: this.pool,
       chain: this.chain,
+      common: this.common,
       minPeers: this.minPeers,
       flow: this.flow,
       interval: this.interval

lib/sync/fastsync.js

@@ -75,6 +75,7 @@ class FastSynchronizer extends Synchronizer {
     this.blockFetcher = new BlockFetcher({
       pool: this.pool,
       chain: this.chain,
+      common: this.common,
       logger: this.logger,
       interval: this.interval,
       first,

lib/sync/fetcher/blockfetcher.js

@@ -64,7 +64,7 @@ class BlockFetcher extends Fetcher {
     let { first, count } = task
     const headers = await peer.eth.getBlockHeaders({ block: first, max: count })
     const bodies = await peer.eth.getBlockBodies(headers.map(h => h.hash()))
-    const blocks = bodies.map((body, i) => new Block([headers[i]].concat(body)))
+    const blocks = bodies.map((body, i) => new Block([headers[i]].concat(body), { common: this.common }))
     return { blocks }
   }
 

lib/sync/fetcher/fetcher.js

@@ -2,9 +2,11 @@
 
 const { Readable, Writable } = require('stream')
 const Heap = require('qheap')
+const Common = require('ethereumjs-common').default
 const { defaultLogger } = require('../../logging')
 
 const defaultOptions = {
+  common: new Common('mainnet', 'chainstart'),
   logger: defaultLogger,
   timeout: 5000,
   interval: 1000,
@@ -24,6 +26,7 @@ class Fetcher extends Readable {
   /**
    * Create new fetcher
    * @param {Object}   options constructor parameters
+   * @param {Common}   options.common common chain config
    * @param {PeerPool} options.pool peer pool
    * @param {number}   [options.timeout] fetch task timeout
    * @param {number}   [options.banTime] how long to ban misbehaving peers
@@ -36,6 +39,7 @@ class Fetcher extends Readable {
     super({ ...options, objectMode: true })
     options = { ...defaultOptions, ...options }
 
+    this.common = options.common
     this.pool = options.pool
     this.logger = options.logger
     this.timeout = options.timeout

lib/sync/lightsync.js

@@ -62,6 +62,7 @@ class LightSynchronizer extends Synchronizer {
     this.headerFetcher = new HeaderFetcher({
       pool: this.pool,
       chain: this.chain,
+      common: this.common,
       flow: this.flow,
       logger: this.logger,
       interval: this.interval,

lib/sync/sync.js

@@ -1,9 +1,11 @@
 'use strict'
 
+const Common = require('ethereumjs-common').default
 const EventEmitter = require('events')
 const { defaultLogger } = require('../logging')
 
 const defaultOptions = {
+  common: new Common('mainnet', 'chainstart'),
   logger: defaultLogger,
   interval: 1000,
   minPeers: 3
@@ -19,6 +21,7 @@ class Synchronizer extends EventEmitter {
    * @param {Object}      options constructor parameters
    * @param {PeerPool}    options.pool peer pool
    * @param {Chain}       options.chain blockchain
+   * @param {Common}      options.common common chain config
    * @param {FlowControl} options.flow flow control manager
    * @param {number}      [options.minPeers=3] number of peers needed before syncing
    * @param {number}      [options.interval] refresh interval
@@ -31,6 +34,7 @@ class Synchronizer extends EventEmitter {
     this.logger = options.logger
     this.pool = options.pool
     this.chain = options.chain
+    this.common = options.common
     this.flow = options.flow
     this.minPeers = options.minPeers
     this.interval = options.interval