Why is `solc.lowlevel.compileCallback` `null` on solc 0.8.12?

[Y-Zeus]

const solc = require('solc');

if (typeof solc.lowlevel.compileSingle != 'function') {
		console.log('Low-level compileSingle interface not implemented by this compiler version.');
}

result:

TypeError: solc.lowlevel.compileCallback is not a function

solc version 0.8.12
why?

[cameel]

These low-level functions were superseded by compile() and are no longer needed (ethereum/solidity#3452). They were removed from the binary in 0.5.0 (ethereum/solidity#5105).

The only reason they're still present under lowlevel is that solc-js is meant to support all compiler binaries, including the ones older than 0.5.0. The check will succeed if you use it with such a binary. For newer ones they're null.

But you have a point in that it's not explained in the README. We should make it clearer.

[Y-Zeus]

thanks

[cameel]

I'll keep this open. I think we should add something about it to the README.

[r0qs]

Fixed by #658.