I am a bit confused by the syntax used in the web3.js file of the ethereum repository, although there is no file named crypto-js nor any npm or yarn, how is this import is being done? https://github.com/ethereum/go-ethereum/blob/master/internal/jsre/deps/web3.js#L1828
The javascript file you're looking at (web3.js) is the result of web3's build, i.e., a browserify bundle of the whole web3 project and its dependencies. The entire crypto-js library from npm is bundled in that file - that's why there's no other references to crypto-js within the go-ethereum project. Let's take a look at the object containing the code you've linked, which looks something like this:
{
//...
19: [
function(require, module, exports) {
//...
var CryptoJS = require('crypto-js');
var sha3 = require('crypto-js/sha3');
//...
},
{
"crypto-js": 59,
"crypto-js/sha3": 80
}
]
//...
}
This key/value pair represents a module. The key 19 is an ID for the module within the bundle. The value is an array with two elements: (1) the module code and (2) the module's dependencies. The dependencies are given as an object with module name keys and module ID values. Thus, the crypto-js module can be found in the same object under key 59, and likewise crypto-js/sha3 under key 80.
Modifying web3.js can be done by obtaining the source and rebuilding it. The version in the go-ethereum repo seems to be 0.20.1, which corresponds to commit 996148d3 in the web3 repository. Building this version is somewhat of a pain, as back then web3 did not commit package-lock.json. I was able to build it by forcing the use of gulp 3.9 and node 10. As for replacing crypto-js, you can edit lib/utils/sha3.js and replace it with a different sha3 implementation.
After rebuilding web3, copy dist/web3-light.js to internals/jsre/deps/web3.js in the go-ethereum repo and run go generate to regenerate internals/jsre/deps/bindata.go. Finally, build geth.
Putting this all together:
# Clone web3
git clone https://github.com/ChainSafe/web3.js
cd web3.js
git switch -c replace-crypto-js 996148d356570745ef20630b499bce37f8484920
# Edit the sha3 implementation
vim lib/utils/sha3.js
# Build using gulp 3.9 and node 10
sed -i 's/"gulp": ">=3.9.0"/"gulp": "^3.9.0"/' package.json
npm install
npm --no-save install node@10
PATH=./node_modules/.bin gulp
# Clone go-ethereum
cd ..
git clone https://github.com/ethereum/go-ethereum.git
cd go-ethereum
# Copy new web3 and regenerate bindata.go
cp ../web3.js/dist/web3-light.js internal/jsre/deps/web3.js
make devtools
PATH=$PATH:$(go env GOPATH)/bin go generate internal/jsre/deps/deps.go
# Build geth and test out changes in console
make geth
./build/bin/geth console