Typescript's Declaration Merging Not Working As Expected Using Ts-node

For a project using the express-session package, I'm trying to mutate the session object by simply adding a user key. req.session.user = 123; Coming from this question's accepted

Solution 1:

LATEST UPDATE (08-MAY-2021)

When running the typescript program by using ts-node, even typeRoots are specified in tsconfig.json, it cannot recognise the custom .d.ts and prompt Property 'x does not exist on type y` error.

According to https://github.com/TypeStrong/ts-node/issues/1132#issuecomment-716642560

One of the contributors of ts-node suggested multiple ways to solve it.

Here is one of it: Specifying file: true flag in tsconfig.json to inform ts-node to load files, include and exclude options from tsconfig.json on startup

{
  "ts-node": {
    "files": true
  },
  "exclude": [...],
  "compilerOptions": {
   ...
}

---

OLD: (07-MAY-2021)

There is no need to use include in tsconfig.json and the paths are not correct. The compiler can search the ts file in the directory and sub-directories

Try to remove it. and restart TS server.

If you are using VSCode, try Cmd + Shift + P or Ctrl + Shift + P and search Restart TS server and see if the user type error still exist

{"exclude":["node_modules"],"compilerOptions":{"lib":["esnext","esnext.asynciterable"],"baseUrl":".","skipLibCheck":true,"module":"commonjs","esModuleInterop":true,"target":"es6","moduleResolution":"node","outDir":"build","experimentalDecorators":true,"emitDecoratorMetadata":true,"allowSyntheticDefaultImports":true,"strict":true,"strictPropertyInitialization":false,},}