@swc/jest incompatible with arrays in .swcrc

[abrenneke]

Similar issue in swc-loader

I'm not exactly sure where the linked documentation in that other issue went, I could have sworn it was on the swc website - but swc supports the .swcrc being an array of configurations to allow one configuration to parse both TS and JS.

@swc/jest assumes that the swcrc is an object, so tries to spread values into it, causing the configuration to get all mangled since an array is spread into an object.

Failed to deserialize buffer as swc::config::Options
    JSON: {"0":{"test":".*.tsx?$","exclude": etc

Version: 0.2.22

.swcrc:

[
  {
    "test": ".*.tsx?$",
    "exclude": ["node_modules", "/lib-types/", "typings", ".*\\.d\\.ts"],
    "jsc": {
      "parser": {
        "syntax": "typescript",
        "tsx": true,
        "decorators": true,
        "dynamicImport": true
      },
      "transform": {
        "legacyDecorator": true
      },
      "target": "es2016",
      "externalHelpers": true
    },
    "module": {
      "type": "commonjs",
      "ignoreDynamic": true
    },
    "sourceMaps": true
  },
  {
    "test": ".*.jsx?$",
    "exclude": ["node_modules", "/lib-types/", "typings"],
    "jsc": {
      "parser": {
        "syntax": "ecmascript",
        "jsx": true,
        "decorators": true,
        "dynamicImport": true,
        "decoratorsBeforeExport": true
      },
      "transform": {
        "legacyDecorator": true
      },
      "target": "es2016",
      "externalHelpers": true
    },
    "module": {
      "type": "commonjs",
      "ignoreDynamic": true
    },
    "sourceMaps": true
  }
]

[craigmiller160]

This issue is definitely real. However, here is a workaround that can allow @swc/jest to work until this is more permanently resolved. This workaround mirrors what is described in the swc-loader issue that OP linked to.

// jest.config.js

const fs = require('fs')

const config = JSON.parse(fs.readFileSync(`${__dirname}/.swcrc`, 'utf-8'))

module.exports = {
    transform: {
        '^.+\\.jsx?$': ['@swc/jest', config[1]],
        '^.+\\.tsx?$': ['@swc/jest', config[0]],
    },
};

[opjarretop]

I hadnt had this issue until upgrading to 0.2.31. upgraded from 0.2.29 which allowed me to use. Curious what changed.

  transform: {
    "^.+\\.(t|j)sx?$": "@swc/jest",
  },