This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

With the suggested changes, modules.getLocalIdent would be allowed to return a falsy value, and in such case, the default getLocalIdent would be used instead.

I am setting up a new project with webpack, I wish to apply the same chain of loaders on different kinds of .scss files:

• main.scss specified as an entry in my configuration, meant to be used as global stylesheet
• App.scss SCSS modules which are imported from their matching component such as App.js

This setup works very well for me, except that main.scss classnames necessarily go through css-loader with modules enabled and using localIdentName.

See the following example:

{
  test: /\.scss$/,
  loader: [
    MiniCSSExtractPlugin.loader,
    {
      loader: 'css-loader',
      options: {
        importLoaders: 1,
        modules: {
          localIdentName: '[name]-[local]__[hash:base64:5]',
        },
      },
    },
    {
      loader: 'sass-loader',
    },
  ],
},

While browsing issues, looking for a way to not use localIdentName for my main.scss file, I stumbled upon #862.
getLocalIdent: () => foo && 'bar' seemed to be a great fit for my use-case.
The behavior introduced in #865 wouldn't have worked for me though, here's what I did instinctively:

modules: {
  localIdentName: '[name]-[local]__[hash:base64:5]',
  getLocalIdent: (context, localIdentName, localName) =>
    context.context.includes('shared/assets/styles') && localName,
},

Note: my main.scss file resides in shared/assets/styles.
This way, my SCSS modules will use localIdentName and main.scss will use localName.

Breaking Changes

None

Additional Info

Thank you for this great package :)
I'm willing to make the final changes if this looks reasonable, thank you in advance for any response.