Developing with Visual Studio Code

We recommend our contributors to use Visual Studio Code with the following extensions installed:

• Prettier - Code Formatter for automatic formatting of source files on save.
• ESLint to highlight and auto-fix linting problems directly in the editor.

Our monorepo comes with few preconfigured VSCode Tasks:

• The build task is configured to run the TypeScript compiler
• The test task is configured to run npm test (which runs the build before running any tests).

How to verify TypeScript setup

Compilation errors

1. Open any existing TypeScript file, e.g. packages/core/src/index.ts

2. Add a small bit of code to break TypeScript’s type checks, for example:

   const foo: number = 'bar';
   

3. Verify that VS Code editor has marked foo with a red underscore. Hover over foo and check the problem message. It should mention [ts] source, e.g.

   [ts] Type '"bar"' is not assignable to type 'number'.
   

4. Check VS Code’s PROBLEMS Window. There should be an entry showing the same eslint error. When you click on the entry, it should jump on the problematic line.

5. Close the editor tab. (This will clear the PROBLEMS entry reported by ESLint extension).

6. Run the test task (“Tasks: Run test task”). This will invoke package scripts like npm test under the hood.

7. Open “Tasks” OUTPUT window and verify that compilation error was parsed by VSCode.

8. Verify that compilation errors are correctly associated with the problematic source code line.

Navigation in VS Code

Verify that “Go to definition” works across package boundaries. Find a place where we are calling @inject in authentication package, press F12 to go to the definition of inject. VSCode should jump to the .ts file in src (as opposed to jumping to a .d.ts file in dist)

Refactoring in VS Code

Verify that refactorings like “rename symbol” (F2) will change all places using the renamed entity. Two different scenarios to verify: rename at the place where the entity is defined, rename at the place where the entity is used. (You can e.g. rename inject to test.)

How to verify ESLint setup

1. Open any existing TypeScript file, e.g. packages/src/index.ts

2. Verify that ESLint extension is not reporting any warnings in the output window:

   • pres Cmd+shift+P or Ctrl+shift+P to open task selector
   • find and run the task ESLint: Show Output
   • check the logs

   An example of a warning we want to avoid:

   Warning: The 'no-unused-variable' rule requires type information.
   

3. Introduce two kinds linting problems - one that does and another that does not require type information to be detected. For example, you can add the following line at the end of the opened index.ts:

   const foo: any = 'bar';
   

4. Verify that VS Code editor has marked any with a red underscore. Hover over any and check the problem message. It should mention no-any rule, e.g.

   [eslint] Type declaration of 'any' loses type-safety. Consider replacing it with a more precise type. (no-any)
   

5. Check VS Code’s PROBLEMS Window. There should be an entry showing the same eslint error. When you click on the entry, it should jump on the problematic line.

6. Close the editor tab. (This will clear the PROBLEMS entry reported by ESLint extension).

7. Run the test task (“Tasks: Run test task”). This will invoke package scripts like npm test under the hood.

8. Open “Tasks” OUTPUT window and verify that two eslint problems were reported:

   ERROR: /Users/(...)/packages/core/src/index.ts[16, 7]: 'foo' is declared but its value is never read.
   ERROR: /Users/(...)/packages/core/src/index.ts[16, 12]: Type declaration of 'any' loses type-safety. Consider replacing it with a more precise type.
   

9. Open “PROBLEMS” window again. Verify that both problems were parsed by VS Code and are correctly associated with the problematic source code line.