[Bug]: Huge performance drop when "allowJs": true is enabled in tsconfig

[LoganTann]

Version

at least since 0.3.3, tried in 0.5.3 and looks even worse (no proofs though)

Steps to reproduce

Minimal reproduction repository : https://github.com/LoganTann/tsjest-performance-issue-reproduction

• Clone the repo
• npm i
• npm run test

Expected behavior

• Jest should take 8 seconds to load the dependency, not more than 10 minutes.

Actual behavior

• Simple test is taking an extremely long time (> 10min) to load the dependency

• Disabling the {allowJs} property in the tsconfig file will make the test run under 8 seconds. However, jest will print over 1400 warnings (executed grep " file to compile while" output_nojs.log | wc -l).

• After a successful run, later tests are expected to be much faster thanks to the caching.

Debug log

Interrupted execution, took too much time.

Additional context

• Running in WSL 2, inside the ~/reproduction/ folder
• No performance issues in the back-end, both in dev and prod. The code compiles and runs fine.
• SWC + vitest is not affected by this issue, but I cannot migrate the whole app in another tech stack.

Performance measures I did five months ago (under 0.3.3)

cross-env NODE_ENV=test jest -runInBand --maxWorkers=1 SalesforceConnections.controller.spec.ts --no-cache

Imports : 
    HttpService: 62226 ms (@nestjs/axios)
    BadRequestException: 1 ms
    ConfigModule: 4736 ms (@nestjs/config)
    Test: 22756 ms (@nestjs/testing)
    TypeOrmModule: 133894 ms (@nestjs/typeorm)
    Repository: 0 ms
    configuration: 9 ms
    RequestUserModel: 8 ms
    CryptoService: 33 ms
    entities: 153 ms
    FixtureService: 109 ms
    TenantEntity: 0 ms
    TenantModel: 5 ms
    TenantService: 34 ms
    UserEntity: 0 ms
    SalesforceConnectionsController: 183104 ms (imports the same)
    SalesforceInstanceDetailsResponseDto: 0 ms
    SalesforceConnectionEntity: 0 ms
    SalesforceInstanceEntity: 0 ms
    SalesforceConnectionService: 0 ms
    SalesforceInstanceService: 0 ms
    SalesforceOauthService: 0 ms
    ConnectivityStatus: 1 ms
Test module compilation :
    Compile: 11315 ms

Environment

System:
    OS: Linux 5.15 Ubuntu 22.04.3 LTS 22.04.3 LTS (Jammy Jellyfish)
    CPU: (8) x64 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
  Binaries:
    Node: 18.19.0 - ~/.nvm/versions/node/v18.19.0/bin/node
    npm: 10.2.3 - ~/.nvm/versions/node/v18.19.0/bin/npm
  npmPackages:
    jest: ^29.7.0 => 29.7.0

[LoganTann]

Related: #1115

[LoganTann]

Found a workaround, suggested by the warning message when you disable "allowJs" :

• Remove "compilerOptions.allowJs": true in your tsconfig file
• Edit the transform regex to select only typescript files with ts-jest :

'transform': {
    '^.+\\.ts$': 'ts-jest', // << selects only ts. It was previously '^.+\\.(j|t)s$'
},

This is still an issue. This needs to be documented, as I had this issue since at least january and I had to investigate since I cleared my jest cache.