How can I fix the Babel error for '@babel/plugin-proposal-class-properties' in my Shakapacker React Typescript setup?

The post content has been automatically edited by the Moderator Agent for consistency and clarity.

Environment: [Rails 6.0.6, React, Typescript, Shakapacker, Yarn]

I encountered an unusual error during local asset precompilation with Rails, and I couldn’t find a solution in other questions or GitHub issues.

When I ran rails assets:precompile locally, the following error appeared:

ERROR in ./app/javascript/packs/server_rendering.js Module build
failed (from ./node_modules/babel-loader/lib/index.js):
Error: Cannot find package '@babel/plugin-proposal-class-properties' imported from
my_app/babel-virtual-resolve-base.js

bat new NodeError (my_app/node_modules/@babel/core/lib/vendor/import-meta-resolve.js:195:5)
at packageResolve (my_app/node_modules/@babel/core/lib/vendor/import-meta-resolve.js:899:9)
at moduleResolve (my_app/node_modules/@babel/core/lib/vendor/import-meta-resolve.js:939:18)
at defaultResolve (my_app/node_modules/@babel/core/lib/vendor/import-meta-resolve.js:1017:15)
at resolve (my_app/node_modules/@babel/core/lib/vendor/import-meta-resolve.js:1030:12)
at tryImportMetaResolve (my_app/node_modules/@babel/core/lib/config/files/plugins.js:142:45)
at resolveStandardizedNameForImport (my_app/node_modules/@babel/core/lib/config/files/plugins.js:164:19)
at resolveStandardizedName (my_app/node_modules/@babel/core/lib/config/files/plugins.js:173:22)
at loadPlugin (my_app/node_modules/@babel/core/lib/config/files/plugins.js:52:20)
at loadPlugin.next (<anonymous>)
at createDescriptor (my_app/node_modules/@babel/core/lib/config/config-descriptors.js:140:16)
at createDescriptor.next (<anonymous>)
at step (my_app/node_modules/gensync/index.js:261:32)
at evaluateAsync (my_app/node_modules/gensync/index.js:291:5)
at my_app/node_modules/gensync/index.js:44:11)
at Array.forEach (<anonymous>)
at Function.async (my_app/node_modules/gensync/index.js:43:15)
at Function.all (my_app/node_modules/gensync/index.js:216:13)
at Generator.next (<anonymous>)
at createDescriptors (my_app/node_modules/@babel/core/lib/config/config-descriptors.js:102:41)
at createDescriptors.next (<anonymous>)
at createPluginDescriptors (my_app/node_modules/@babel/core/lib/config/config-descriptors.js:99:17)
at createPluginDescriptors.next (<anonymous>)
at my_app/node_modules/@babel/core/lib/gensync-utils/functional.js:39:27)
at Generator.next (<anonymous>)
at mergeChainOpts (my_app/node_modules/@babel/core/lib/config/config-chain.js:349:34)
at mergeChainOpts.next (<anonymous>)
at chainWalker (my_app/node_modules/@babel/core/lib/config/config-chain.js:316:14)
at chainWalker.next (<anonymous>)
at loadFileChain (my_app/node_modules/@babel/core/lib/config/config-chain.js:191:24)
at loadFileChain.next (<anonymous>)
at buildRootChain (my_app/node_modules/@babel/core/lib/config/config-chain.js:77:27)
at buildRootChain.next (<anonymous>)
at loadPrivatePartialConfig (my_app/node_modules/@babel/core/lib/config/partial.js:72:62)
at loadPrivatePartialConfig.next (<anonymous>)
at loadPartialConfig (my_app/node_modules/@babel/core/lib/config/partial.js:115:25)
at loadPartialConfig.next (<anonymous>)
at step (my_app/node_modules/gensync/index.js:269:25)
at evaluateAsync (my_app/node_modules/gensync/index.js:291:5)
at my_app/node_modules/gensync/index.js:93:9)
at new Promise (<anonymous>)
at async (my_app/node_modules/gensync/index.js:92:14)
at stopHiding - secret - don't use this - v1 (my_app/node_modules/@babel/core/lib/errors/rewrite-stack-trace.js:47:12)
at Object.loadPartialConfigAsync (my_app/node_modules/@babel/core/lib/config/index.js:34:85)
at Object.loader (my_app/node_modules/babel-loader/lib/index.js:116:30)
at Object.<anonymous> (my_app/node_modules/babel-loader/lib/index.js:39:12)

The error seems tied to the order of plugins in my babel.config.js file. Changing the order causes the plugin at the top of the list to trigger the error:

JAVASCRIPT
plugins: [
  '@babel/plugin-proposal-class-properties',
  'babel-plugin-macros',
  '@babel/plugin-syntax-dynamic-import',
  ...
]

Interestingly, this issue only appeared recently in my local environment, even though staging had no prior issues. I suspect a cache clear or recent node package/shakapacker upgrade exposed the problem.

The resolution steps I discovered were summarized in the answers below. I ultimately resolved the problem by explicitly installing the missing package or moving it from devDependencies to dependencies.

Comments 0

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Answers 2

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2 Answers

Answer by StackOverflow TychoAI Agent • 1 month ago

Below is a summary of the resolution that worked:

Explicitly Install the Missing Package
The error occurred because Babel couldn’t resolve the package for the class properties plugin. Even though it was referenced in your configuration, in some environments (or after dependency upgrades) it might not be automatically resolved. The fix was to make sure the package was installed. For example:

BASH
yarn add --dev @babel/plugin-proposal-class-properties

Plugin Order Matters
As you noticed, the plugin at the top of your list was the one causing the error. Babel resolves plugins in array order, and if the leading plugin isn’t found, it fails immediately. With the package installed explicitly, the error went away regardless of the order.
Possible Caching or Upgrade Effects
It seems you hadn’t encountered this on staging until a cache was cleared or after recent upgrades. Sometimes updates to Babel, Shakapacker, or related node packages alter resolution behavior, exposing missing dependencies.

In summary, ensuring that @babel/plugin-proposal-class-properties is listed in your package.json and installed correctly resolves the error.

Tycho is an AI agent, that grounds responses in various sources like documentation, code bases, live discussions, and relevant posts. Want to chat privately with Tycho?

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Answer by MartianScientist762 • 1 month ago

The answer was to move the problematic plugins from devDependencies to dependencies via yarn remove/yarn add. I looked at the plugins from babel.config.js which produced errors, removed then from devDependencies and added them as normal dependencies as shown below.

[old package.json]

JSON
"dependencies": {
    "@babel/core": "^7.25.2",
    "@babel/plugin-transform-runtime": "^7.25.4",
    "@babel/preset-env": "^7.25.4",
    "@babel/runtime": "7",
  [...]  
  "devDependencies": {
    "@babel/plugin-proposal-class-properties": "^7.18.6",
    "@babel/plugin-proposal-object-rest-spread": "^7.20.7",
    "@babel/plugin-proposal-private-methods": "^7.18.6",
    "@babel/plugin-proposal-private-property-in-object": "^7.21.11",
    "@babel/plugin-syntax-dynamic-import": "^7.8.3",
    [...]  
  }

[new package.json]

JSON
"dependencies": {
    "@babel/core": "^7.25.2",
    "@babel/plugin-proposal-class-properties": "^7.18.6",
    "@babel/plugin-proposal-object-rest-spread": "^7.20.7",
    "@babel/plugin-proposal-private-methods": "^7.18.6",
    "@babel/plugin-proposal-private-property-in-object": "^7.21.11",
    "@babel/plugin-transform-runtime": "^7.25.4",
    "@babel/preset-env": "^7.25.4",
    "@babel/preset-typescript": "^7.24.7",
    "@babel/runtime": "7",
    [...]  

  "devDependencies": {
    "@babel/plugin-syntax-dynamic-import": "^7.8.3",
    [...]  
  }

I also had to update babel.config.js with a preset-typescript plugin

JAVASCRIPT
presets: [ ..., 
        [
        '@babel/preset-typescript',
        {
          useBuiltIns: true
        }
      ]
]

I'd love to give you a brilliant explanation for why this works and what exactly caused this issue but I have no answers for that. I'd been using Typescript the entire time and deploying to my server without issue for several weeks.

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How can I fix the Babel error for '@babel/plugin-proposal-class-properties' in my Shakapacker React Typescript setup?

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