tsc throws `TS2307: Cannot find module` for a local file

Question

@vladima replied to this issue on GitHub:

The way the compiler resolves modules is controlled by moduleResolution option that can be either node or classic (more details and differences can be found here). If this setting is omitted the compiler treats this setting to be node if module is commonjs and classic - otherwise. In your case if you want classic module resolution strategy to be used with commonjs modules - you need to set it explicitly by using

{
    "compilerOptions": {
        "moduleResolution": "node"
    }
}

In some cases you just need to update the include array.

{
  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "moduleResolution": "node",
    "outDir": "dist",
    "sourceMap": false,
    "baseUrl": ".",
    "paths": {
      "@/*": ["src/*"]
    }
  },
  "include": ["src/**/*.ts", "tests/**/*.ts"],
  "exclude": ["node_modules", ".vscode"]
}

In VS2019, the project property page, TypeScript Build tab has a setting (dropdown) for "Module System". When I changed that from "ES2015" to CommonJS, then VS2019 IDE stopped complaining that it could find neither axios nor redux-thunk (TS2307).

tsconfig.json:

{
  "compilerOptions": {
    "allowJs": true,
    "baseUrl": "src",
    "forceConsistentCasingInFileNames": true,
    "jsx": "react",
    "lib": [
      "es6",
      "dom",
      "es2015.promise"
    ],
    "module": "esnext",
    "moduleResolution": "node",
    "noImplicitAny": true,
    "noImplicitReturns": true,
    "noImplicitThis": true,
    "noUnusedLocals": true,
    "outDir": "build/dist",
    "rootDir": "src",
    "sourceMap": true,
    "strictNullChecks": true,
    "suppressImplicitAnyIndexErrors": true,
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true,
    "target": "es5",
    "skipLibCheck": true,
    "strict": true,
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true
  },
  "exclude": [
    "build",
    "scripts",
    "acceptance-tests",
    "webpack",
    "jest",
    "src/setupTests.ts",
    "node_modules",
    "obj",
    "**/*.spec.ts"
  ],
  "include": [
    "src",
    "src/**/*.ts",
    "@types/**/*.d.ts",
    "node_modules/axios",
    "node_modules/redux-thunk"
  ]
}

The vscode codebase does not use relative paths, but everything works fine for them

Really depends on your module loader. If you are using systemjs with baseurl then it would work. VSCode uses its own custom module loader (based on an old version of requirejs).

Recommendation

Use relative paths as that is what commonjs supports. If you move files around you will get a typescript compile time error (a good thing) so you will be better off than a great majority of pure js projects out there (on npm).