when a string param is empty in data then decodeLog throws "The parameter "0x" must be a valid HEX string."

[szerintedmi]

web3@1.0.0-beta.20

It seems web3.eth.abi.decodeLog doesn't handle cases when a string data in event log is empty, it throws:

Uncaught Error: The parameter "0x" must be a valid HEX string.
    at Object.hexToUtf8 (utils.js:186)
    at SolidityTypeString.formatOutputString [as _outputFormatter] (formatters.js:209)
    at type.js:246
    at SolidityTypeString../node_modules/web3/packages/web3-eth-abi/src/types/type.js.SolidityType.decode (type.js:247)
    at index.js:322
    at Array.forEach (<anonymous>)
    at ABICoder../node_modules/web3/packages/web3-eth-abi/src/index.js.ABICoder.decodeParameters (index.js:321)
    at ABICoder../node_modules/web3/packages/web3-eth-abi/src/index.js.ABICoder.decodeLog (index.js:363)
    at abi-decoder.js:181
    at Array.map (<anonymous>)
    at Object.decodeLogs (abi-decoder.js:119)
    at XMLHttpRequest.xhr.onreadystatechange (ethHelper.js:150)

To reproduce, based on
Tx1 (param "narrative" is "test x" in data) and Tx2 (param "narrative" is "" in data)

let _inputs = [
                { indexed: true, name: "from", type: "address" },
                { indexed: true, name: "to", type: "address" },
                { indexed: false, name: "amount", type: "uint256" },
                { indexed: false, name: "narrative", type: "string" }
            ];
            let _topics = [
                "0x000000000000000000000000ae653250b4220835050b75d3bc91433246903a95",
                "0x00000000000000000000000094011c67bc1e6448ed4b8682047358ca6cd09470"
            ];

            let _logDataTx1 =
                "0x0000000000000000000000000000000000000000000000000000000000002710000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000067465737420780000000000000000000000000000000000000000000000000000";
            let _logDataTx2 =
                "0x000000000000000000000000000000000000000000000000000000000000271000000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000000";

            let _decodedDataTx1 = web3.eth.abi.decodeLog(
                _inputs,
                _logDataTx1,
                _topics
            );
            console.log("Decoded data Tx1:", _decodedDataTx1);
// ^^^^ output is correct, last param is there ^^^^
            let _decodedDataTx2 = web3.eth.abi.decodeLog(
                _inputs,
                _logDataTx2,
                _topics
            );
// ^^^^  Throws: Uncaught Error: The parameter "0x" must be a valid HEX string. ^^^^ 
            console.log("Decoded data Tx2:", _decodedDataTx2);

[frozeman]

The current 1.0 branch will result in the following:

>             web3.eth.abi.decodeLog(_inputs,_logDataTx1,_topics);
Result {
  '0': '0xae653250B4220835050B75D3bC91433246903A95',
  '1': '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  '2': '10000',
  '3': 'test x',
  __length__: 4,
  from: '0xae653250B4220835050B75D3bC91433246903A95',
  to: '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  amount: '10000',
  narrative: 'test x' }
>
>             web3.eth.abi.decodeLog(_inputs,_logDataTx2,_topics);
Result {
  '0': '0xae653250B4220835050B75D3bC91433246903A95',
  '1': '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  '2': '10000',
  __length__: 4,
  from: '0xae653250B4220835050B75D3bC91433246903A95',
  to: '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  amount: '10000',
  narrative: undefined }

I would have to dig deeper, to figure out how i can make it return an empty string here, as we use the same coder also for call return values etc.

[szerintedmi]

Great, thanks. Is it a released branch? If so I will test it.
I'm already happy with undefined - that would make it possible to get rid of the current ugly, complex & non-generic workaround we had to add :)

[frozeman]

I can make a beta release now.

[frozeman]

will be as follows:

>             web3.eth.abi.decodeLog(_inputs,_logDataTx1,_topics);
Result {
  '0': '0xae653250B4220835050B75D3bC91433246903A95',
  '1': '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  '2': '10000',
  '3': 'test x',
  __length__: 4,
  from: '0xae653250B4220835050B75D3bC91433246903A95',
  to: '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  amount: '10000',
  narrative: 'test x' }
>
>             web3.eth.abi.decodeLog(_inputs,_logDataTx2,_topics);
Result {
  '0': '0xae653250B4220835050B75D3bC91433246903A95',
  '1': '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  '2': '10000',
  '3': '',
  __length__: 4,
  from: '0xae653250B4220835050B75D3bC91433246903A95',
  to: '0x94011c67BC1E6448ed4b8682047358ca6cD09470',
  amount: '10000',
  narrative: '' }

[frozeman]

released beta 21

[szerintedmi]

works fine with 1.0.0-beta.21, thank you