Instrumenting bundled code with TypeScript

DEBUG=code-coverage yarn cypress open と @cypress/code-coverage/use-babelrc の設定を使って失敗を再現します。まず、ログに記載された TypeScript ファイル（cypress/support/index.ts と cypress/tests/api/handle.spec.ts を含む）から始め、その後、報告された NYC の設定を調べます。完了条件は、Cypress の TypeScript テストがインストルメントされ、そのカバレッジが lib/api/handle.ts に対して含まれることです。

Logs and screenshots
Please provide debug logs by running Cypress from the terminal with DEBUG=code-coverage environment variable set, see the Debugging section of the README file.

nchiang@garchomp ~/repos/thavma (master) $ DEBUG=code-coverage yarn cypress open
  code-coverage combined NYC options { 'report-dir': './coverage', reporter: [ 'html', 'json' ], extension: [ '.js', '.cjs', '.mjs', '.ts', '.tsx', '.jsx' ], excludeAfterRemap: false, all: true, extends: '@istanbuljs/nyc-config-typescript', include: [ 'pages/**', 'components/**', 'lib/**' ], exclude: [ 'pages/api/coverage.ts', '**/*.d.ts' ] } +0ms
Loaded env from /Users/nchiang/repos/thavma/.env.test.local
Loaded env from /Users/nchiang/repos/thavma/.env.local
Loaded env from /Users/nchiang/repos/thavma/.env.test
Loaded env from /Users/nchiang/repos/thavma/.env
GET /__/ 200 17.288 ms - -
GET /__cypress/runner/cypress_runner.css 200 18.783 ms - -
GET /__cypress/runner/cypress_runner.js 200 4.865 ms - -
GET /__cypress/runner/favicon.ico 200 1.298 ms - -
GET /__cypress/runner/fonts/fa-solid-900.woff2 200 1.584 ms - 76120
GET /__cypress/runner/fonts/mulish-latin-400-normal.woff2 200 1.354 ms - 31176
GET /__cypress/runner/fonts/mulish-latin-500-normal.woff2 200 1.916 ms - 31176
GET /__cypress/runner/fonts/open-sans-latin-400-normal.woff2 200 15.233 ms - 14380
GET /__cypress/iframes/__all 200 20.262 ms - -
Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/support/index.ts
GET /__cypress/tests?p=cypress/support/index.ts 200 26.500 ms - 674
Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/tests/api/handle.spec.ts
Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/tests/api/users.spec.ts
Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/tests/index.spec.ts
Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/tests/join.spec.ts
GET /__cypress/tests?p=cypress/tests/api/handle.spec.ts 200 22.968 ms - 682
GET /__cypress/tests?p=cypress/tests/api/users.spec.ts 200 21.953 ms - 681
GET /__cypress/tests?p=cypress/tests/index.spec.ts 200 20.687 ms - 677
GET /__cypress/tests?p=cypress/tests/join.spec.ts 200 20.259 ms - 676

Versions

• What is this plugin's version? If this is NOT the latest released version can you try the latest version, please? 3.9.11
• If the plugin worked before in version X, but stopped after upgrading to version Y, please try the released versions between X and Y to see where the breaking change was.
• What is Cypress version?

Cypress package version: 8.7.0
Cypress binary version: 8.7.0
Electron version: 14.1.0
Bundled Node version: 14.17.0

• What is your operating system? MacOS Big Sur
• What is the shell? Bash
• What is the Node version? 16.13.0
• What is the NPM version? 8.1.0
• How do you instrument your application? Cypress does not instrument web application code, so you need to do it yourself. Yes! But I can't seem to instrument the bundled Cypress test code.
• When running tests, if you open the web application in regular browser, and open DevTools, do you see window.__coverage__ object? Can you paste a screenshot?
• Is there .nyc_output folder? Is there .nyc_output/out.json file. Is it empty? Can you paste at least part of it so we can see the keys and file paths?
• Do you have any custom NYC settings in package.json (nyc object) or in other NYC config files

// nyc.config.js
/**
 * Code coverage configuration for use with Cypress and Typescript.
 * @see {@link https://docs.cypress.io/guides/tooling/code-coverage.html}
 * @see {@link https://github.com/istanbuljs/nyc#selecting-files-for-coverage}
 */
module.exports = {
  all: true,
  extends: '@istanbuljs/nyc-config-typescript',
  reporter: ['html', 'json'],
  include: ['pages/**', 'components/**', 'lib/**'],
  exclude: ['pages/api/coverage.ts', '**/*.d.ts'],
};

• Do you run Cypress tests in a Docker container? No.

Describe the bug
A clear and concise description of what the bug is.

I've been trying to follow your guide on achieving 100% code coverage by combining unit tests with E2E integration tests. But, all my application code is written in TypeScript and when I use the @cypress/code-coverage/use-babelrc package, I get the following error:

Error running @cypress/browserify-preprocessor:

You are attempting to preprocess a TypeScript file, but do not have TypeScript configured. Pass the 'typescript' option to enable TypeScript support.

The file: /Users/nchiang/repos/thavma/cypress/support/index.ts

Link to the repo
Bugs with a reproducible example, like an open source repo showing the bug, are the most likely to be resolved.

thavmaclub/thavma illustrates this issue; the test coverage reports that lib/api/handle.ts wasn't covered entirely, but I have unit tests just for that. However, those unit tests aren't included in the test coverage because they're not instrumented because of this bug.

Example
See #217 that is an excellent bug report example