Extremely slow coverage with v8, and nestjs while using testing modules

[Seboran]

Describe the bug

When running coverage on a nestjs project which uses @nestjs/testing, the report is very slow to report.

On my machine (Macbook pro M2), it takes around 1m for one test with one mock.

It looks like #5252, but the PR still doesn't fix the issue on my machine (if I linked the project correctly on my machine).

Maybe there is something I don't understand with nestjs that makes coverages extremely slow?

Reproduction

1. Clone and install https://github.com/Seboran/nest-js-slow-coverage
2. run pnpm vitest run --coverage
3. wait for coverage to take close to a minute even tho there is only one test that does one thing
4. check https://github.com/Seboran/nest-js-slow-coverage/blob/main/src/tools/__test__/test.service.spec.ts and see that the test doesn't do a lot

System Info

System:
    OS: macOS 14.2.1
    CPU: (10) arm64 Apple M2 Pro
    Memory: 304.98 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.5.0 - ~/.nvm/versions/node/v20.5.0/bin/node
    Yarn: 1.22.19 - /opt/homebrew/bin/yarn
    npm: 10.1.0 - ~/.nvm/versions/node/v20.5.0/bin/npm
    pnpm: 8.5.1 - /opt/homebrew/bin/pnpm
    bun: 1.0.18 - ~/.bun/bin/bun
  Browsers:
    Safari: 17.2.1
  npmPackages:
    @vitest/coverage-v8: ^1.3.1 => 1.3.1
    @vitest/ui: ^1.3.1 => 1.3.1
    vitest: ^1.3.1 => 1.3.1

Used Package Manager

pnpm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[AriPerkkio]

It looks like #5252, but the PR still doesn't fix the issue on my machine (if I linked the project correctly on my machine).

This is indeed duplicate of #5252. By patching the fix from #5259 your reproduction works fast.

• package.json

  "pnpm": {
    "patchedDependencies": {
      "@vitest/coverage-v8@1.3.1": "patches/@vitest__coverage-v8@1.3.1.patch"
    }

• patches/@vitest__coverage-v8@1.3.1.patch

diff --git a/dist/provider.js b/dist/provider.js
index 408c1c8d7c5053bd9d2d053717ea6d86140b34e9..0a15cfc5c641f3ecf4f1320d88a71524c8a2bac7 100644
--- a/dist/provider.js
+++ b/dist/provider.js
@@ -170,7 +170,7 @@ function cleanUrl(url) {
 
 const WRAPPER_LENGTH = 185;
 const VITE_EXPORTS_LINE_PATTERN = /Object\.defineProperty\(__vite_ssr_exports__.*\n/g;
-const DECORATOR_METADATA_PATTERN = /_ts_metadata\("design:paramtypes"(\s|.)+?]\),/g;
+const DECORATOR_METADATA_PATTERN = /_ts_metadata\("design:paramtypes", \[[^\]]*?\]\),*/g;
 const DEFAULT_PROJECT = Symbol.for("default-project");
 const debug = createDebug("vitest:coverage");
 let uniqueId = 0;

$ time pnpm run test:cov --run

> backend@0.0.1 test:cov /workspaces/nest-js-slow-coverage
> vitest --coverage "--run"

The CJS build of Vite's Node API is deprecated. See https://vitejs.dev/guide/troubleshooting.html#vite-cjs-node-api-deprecated for more details.

 RUN  v1.3.1 /workspaces/nest-js-slow-coverage
      Coverage enabled with v8

 ✓ src/tools/__test__/test.service.spec.ts (1)
   ✓ ToolsService (1)
     ✓ createTool (1)
       ✓ should create a new tool

 Test Files  1 passed (1)
      Tests  1 passed (1)
   Start at  07:37:35
   Duration  898ms (transform 114ms, setup 0ms, collect 513ms, tests 12ms, environment 0ms, prepare 132ms)

 % Coverage report from v8
-------------------|---------|----------|---------|---------|-------------------
File               | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-------------------|---------|----------|---------|---------|-------------------
All files          |   46.83 |       25 |   16.66 |   46.83 |                   
 src               |       0 |        0 |       0 |       0 |                   
  app.module.ts    |       0 |        0 |       0 |       0 | 1-15              
  main.ts          |       0 |        0 |       0 |       0 | 1-15              
 src/schemas       |     100 |      100 |     100 |     100 |                   
  tool.schema.ts   |     100 |      100 |     100 |     100 |                   
 src/tools         |      80 |      100 |   33.33 |      80 |                   
  tools.service.ts |      80 |      100 |   33.33 |      80 | 14-15,18-19       
 src/tools/mock    |       0 |        0 |       0 |       0 |                   
  MockToolModel.ts |       0 |        0 |       0 |       0 | 1-8               
-------------------|---------|----------|---------|---------|-------------------

real    0m2.411s
user    0m2.099s
sys     0m1.313s

[Seboran]

Oops sorry for the duplicate and thank you for the answer 😄