Webpack 5 webpackMissingModule error for node_modules package - node.js

Question

I've been working on upgrading a repository from Webpack version 4 to 5, and I've encountered a very strange problem where Webpack will throw an error at runtime telling me that a package in node_modules could not include a specific "module" (referring to a subdirectory of that package). The module in question is #hapi/joi, and the error I'm receiving is:
Error: Cannot find module './types/alternatives'
At one point it was telling me that the error related to that package, but now it just throws the error with no package context. I've dug into the #hapi/joi package, and I can see this set of imports in the index.js:
const internals = {
alternatives: require('./types/alternatives'),
array: require('./types/array'),
boolean: require('./types/boolean'),
binary: require('./types/binary'),
date: require('./types/date'),
func: require('./types/func'),
number: require('./types/number'),
object: require('./types/object'),
string: require('./types/string'),
symbol: require('./types/symbol')
};
I've verified that the ./types/alternatives directory exists and that it has an index.js of its own. This package also works fine on Webpack 4. I tried upgrading to the standalone joi package, and it threw the same error.
I'm pretty confused at to why this error is throw at runtime. I would think this would be a build error, though maybe it has something to do with building the target for node?
This is my Webpack config. It's mostly unmodified from v4:
{
entry: {
adviceServer: "./src/server/index.ts",
},
target: "node",
bail: true,
mode: env.NODE_ENV,
output: {
path: path.resolve(root, "dist", "js"),
filename: `[name].${env.ASSET_HASH}.js`
},
module: {
rules: [
{
test: /\.tsx?$/,
use: [
{
loader: "ts-loader",
options: {
context: path.resolve(root, "src"),
configFile: tsconfigPath,
transpileOnly: false
}
}
],
exclude: [
"/node_modules",
"/**/*.test.ts/"
]
},
{
test: /\.s?css$/,
use: ["isomorphic-style-loader", "css-loader", "sass-loader"]
}
]
},
resolve: {
extensions: [".tsx", ".ts", ".js", ".jsx", "scss", ".json"],
alias: {
styles: path.resolve(root, "src", "scss"),
canvas: path.resolve(root, "src", "etc", "fileMock"),
ws: path.resolve(root, "src", "etc", "fileMock")
},
plugins: [
new TsconfigPathsPlugin({
configFile: tsconfigPath
})
]
},
devtool: "eval-cheap-source-map",
plugins: [
new BundleTracker({ filename: "./webpack-stats.json" })
]
}

Answer 1

I had a similar issue upgrading from webpack 4 but with a different external library. In my case it was caused by two webpack#5 versions installed at the same time. Check your package-lock.json/yarn.lock and add overrides/resolutions to your package.json if there are several versions. If not — try removing your node_modules folder and installing packages again.