reside-eng / jest-runtime

Custom runtime for Jest which addresses memory issue

@side/jest-runtime

Custom runtime for Jest which addresses memory leak when using Typescript

NOTE This package was intentionally left as JS instead of being converted to TS because it is only a slight modification of existing Jest code based on this PR

1. Install SWC if you haven't already @swc/core @swc/jest

2. Make sure to configure SWC if you haven't already:

   {
      "jsc": {
         "parser": {
            "syntax": "typescript",
            "decorators": true
         },
         "transform": {
            "legacyDecorator": true,
            "decoratorMetadata": true
         }
      }
   }
   

3. Install custom runtime: yarn add @side/jest-runtime

4. Use within jest.config.js:

   module.exports = {
     transform: {
       '^.+\\.ts$': '@swc/jest',
     },
     runtime: '@side/jest-runtime',
   };

Why?

We were seeing memory leaks using ts-jest with node >16.10. When investigating solutions this PR fixing the issue was noticed. Since it hasn't been merged, and we still wanted to share this logic, we created this lib.

jest-runtime's Issues

V8 code coverage broken when using this runtime

We're using the coverageProvider v8 in Jest 28.1.3 and have full code coverage for our app (for all code that is not ignored specifically), but are also experiencing the devastating memory leak your runtime is fixing. With your runtime enabled, a lot of previously covered lines are suddenly shown as uncovered, including imports and empty lines.

Are you aware of this issue? Would it be worth trying to pull in the latest version of https://github.com/facebook/jest/blob/main/packages/jest-runtime/src/index.ts?

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Detected dependencies

github-actions

.github/workflows/release.yml

• actions/checkout v3
• actions/setup-node v3
• cycjimmy/semantic-release-action v2
• actions/checkout v3
• technote-space/workflow-conclusion-action v2.2.2
• reside-eng/workflow-status-notification-action v1.0.7

.github/workflows/verify.yml

• actions/checkout v3
• actions/setup-node v3

npm

package.json

• @commitlint/cli 17.0.2
• @side/commitlint-config 0.1.10
• @side/eslint-config-base 0.14.0
• @side/eslint-config-jest 0.4.0
• @side/prettier-config 0.0.0
• eslint 8.17.0
• eslint-config-prettier 8.5.0
• eslint-plugin-jsdoc 38.1.6
• husky 7.0.4
• jest 28.1.1
• lint-staged 12.5.0
• prettier 2.7.0
• rimraf 3.0.2
• jest ^28
• node >=16

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Jest v29 support

Looks like the memory leak is still there in v29, any chance to upgrade this package to support it?

Undeclared dependencies

Getting this error when using yarn to install and run this, seems you need to add jest-runtime and @jest/transform to the package.json as dependencies or peerDependencies.

@side/jest-runtime tried to access jest-runtime, but it isn't declared in its dependencies; this makes the require call ambiguous and unsound.
 @side/jest-runtime tried to access @jest/transform, but it isn't declared in its dependencies; this makes the require call ambiguous and unsound.

Node 16 required?

Any particular reason for requiring node 16? The package seems to be working just fine on node 14 too (a CI run as a proof), and I dont see anything that would require higher version.