When TSC suddenly errors with cannot find module

2021-01-16

TLDR

• If you have this error, double-check if your rootDir is consistent.
• I got this error from TSC, auto-flattening the folder structure.

On my TypeScript Node Server, I suddenly got the following error on the tsc command for production settings.

internal/modules/cjs/loader.js:{number}
  throw err;

Error: Cannot find module '{project}/dist'
  at ... {
  code: 'MODULE_NOT_FOUND',
  requireStack: []
}

Then I stashed my work and started traveling back in time with git checkout HASH. Comes out, the error started when I added MongoDB Models at src/models.

It seemed strange since it had nothing to do with adding new modules or dependencies. Reinstalling node_modules did not do the job for me (Relevant Stack Overflow Question here). Please take a look at my folder structure.

.
├── LICENSE
├── README.md
├── dist
├── package-lock.json
├── package.json
├── src
│   ├── models (Newly added. Started to cause an error.)
│   │   └── user.ts (Newly added. Started to cause an error.)
│   └── server
│       ├── config
│       │   ├── config.ts
│       │   ├── dev.env
│       │   ├── dev.env.sample
│       │   ├── prod.env
│       │   └── prod.env.sample
│       └── index.ts
└── tsconfig.json

Long story short, it was the problem in my tsconfig. I have previously declared the following statement on my tsconfig.

{
  ...
  "include": ["src/**/*"]
}

However, since there was only a /server folder before creating the model, it seems that TSC has automatically set the root directory to src/server. Therefore the dist output seemed like the following.

dist
├── config
│   ├── config.js
│   └── prod.env
└── index.js

But after models/user.ts was added, src contained both models and server directories, recognizing the root directory as src. So it now became:

dist
├── models
│   └── user.js
└── server
    ├── config
    │   ├── config.js
    │   └── prod.env
    └── index.js

Notice the directory structure has changed. My entire npm commands were based as if src/server was a root directory (as if the index was at dist/index.js), so that began to cause the error. Therefore I updated the npm commands. Note that I changed dists to dist/servers.

rm -rf dist
&& tsc
- && cp ./src/server/config/prod.env ./dist/config/prod.env
&& export NODE_ENV=prod
- && node dist

rm -rf dist
&& tsc
+ && cp ./src/server/config/prod.env ./dist/server/config/prod.env
&& export NODE_ENV=prod
+ && node dist/server

To prevent TSC from guessing the root directory, you can add the following line on your tsconfig.json.

{
  "compilerOptions": {
    ...
    "rootDir": "src",
  }
}

This line will retain the absolute folder structure from src.