What does “The code generator has deoptimised the

问题:

I added a new npm package to my project and require it in one of my modules.

Now I get this message from webpack,

build modulesNote: The code generator has deoptimised the styling of "D:/path/to/project/node_modules/ramda/dist/ramda.js" as it exceeds the max of "100KB".

What does it mean? Do I need to take some action?

回答1:

This is related to compact option of Babel compiler, which commands to "not include superfluous whitespace characters and line terminators. When set to 'auto' compact is set to true on input sizes of >100KB." By default its value is "auto", so that is probably the reason you are getting the warning message. See Babel documentation.

You can change this option from Webpack using a query parameter. For example:

loaders: [
    { test: /\.js$/, loader: 'babel', query: {compact: false} }
]

回答2:

This seems to be a Babel error. I'm guessing you use babel-loader, and are not excluding external libraries from your loader test. As far as I can tell, the message is not harmful, but you should still do something like this:

loaders: [
    { test: /\.js$/, exclude: /node_modules/, loader: 'babel' }
]

Have a look. Was that it?

回答3:

Either one of the below three options gets rid of the message (but for different reasons and with different side-effects I suppose):

1. exclude the node_modules directory or explicitly include the directory where your app resides (which presumably does not contain files in excess of 100KB)
2. set the Babel option compact to true (actually any value other than "auto")
3. set the Babel option compact to false (see above)

#1 in the above list can be achieved by either excluding the node_modules directory or be explicitly including the directory where your app resides.

E.g. in webpack.config.js:

let path = require('path');
....
module: {
     loaders: [
          ...
          loader: 'babel',
          exclude: path.resolve(__dirname, 'node_modules/')

... or by using include: path.resolve(__dirname, 'app/') (again in webpack.config.js).

#2 and #3 in the above list can be accomplished by the method suggested in this answer or (my preference) by editing the .babelrc file. E.g.:

$ cat .babelrc 
{
    "presets": ["es2015", "react"],
    "compact" : true
}

Tested with the following setup:

$ npm ls --depth 0 | grep babel
├── babel-core@6.7.4
├── babel-loader@6.2.4
├── babel-preset-es2015@6.6.0
├── babel-preset-react@6.5.0

回答4:

I tried Ricardo Stuven's way but it didn't work for me. What worked in the end was adding "compact": false to my .babelrc file:

{
    "compact": false,
    "presets": ["latest", "react", "stage-0"]
}

回答5:

In react/redux/webpack/babel build fixed this error by removing script tag type text/babel

got error:

<script type="text/babel" src="/js/bundle.js"></script>

no error:

<script src="/js/bundle.js"></script>

回答6:

For more explanation read THIS LINK, it is option of Babel compiler that commands to not include superfluous whitespace characters and line terminators. some times ago its threshold was 100KB but now is 500KB.

I proffer you disable this option in your development environment, with this code in .babelrc file.

{
    "env": {
      "development" : {
        "compact": false
      }
    }
}

For production environment Babel use the default config which is auto.

回答7:

this warrning has happened to me and finally got a FATAL ERROR: MarkCompactCollector: semi-space copy, fallback in old gen Allocation failed - JavaScript heap out of memory. the reason was that i dynamically imported the current module, so this ended up with an endless loop...

回答8:

in webpack 4 with multiple module rules you would just do something like this in your .js rule: { test: /\.(js)$/, loader: 'babel-loader', options: { presets: ['es2015'], // or whatever plugins: [require('babel-plugin-transform-class-properties')], // or whatever compact: true // or false during development } },