Discussion: How web3 coerces strings into bytes32

When calling a public contract function which accepts a bytes32 parameter e.g. function createNetwork(bytes32 name) with an Ascii string:

rootNetwork.functions.createNetwork('test');

Error is thrown: Uncaught (in promise) Error: invalid arrayify value

Other contract function return correctly in this instance, implying wiring of the contract is correct.

[ricmoo]

Oh! The string you sent is the full bytes sent to the network, including the function selector.

To mimic the web3 coercion of short string into bytes32 you can use the following; but please be aware you are relying on incorrect behaviour, so terrible things will happen, if for example the string is over 32 bytes (not necessarily characters) long:

function web3StringToBytes32(text) {
    var result = ethers.utils.hexlify(ethers.utils.toUtf8Bytes(text));
    while (result.length < 66) { result += '0'; }
    if (result.length !== 66) { throw new Error("invalid web3 implicit bytes32"); }
    return result;
}

[elenadimitrova]

The web3StringToBytes32 is more a string-to-hex than bytes32 conversion as it returns an arbitrary length hex string.

From my part we can close this as I’ve gone up to v1 of web3.utils which has a utf8ToHex, asciiToHex and a handful of other useful conversion functions http://web3js.readthedocs.io/en/1.0/web3-utils.html?highlight=toUTF#utf8tohex

Also, the auto conversion between strings (used as keys) and their encoded bytes32 hex equivalent has been discussed here well before the v1 release above https://github.com/ethereum/web3.js/issues/271 including comments from “the author of Solidity” 😃