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    @rollup/plugin-dynamic-import-vars

    1.1.1 • Public • Published

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    @rollup/plugin-dynamic-import-vars

    🍣 A rollup plugin to support variables in dynamic imports in Rollup.

    function importLocale(locale) {
      return import(`./locales/${locale}.js`);
    }

    Requirements

    This plugin requires an LTS Node version (v10.0.0+) and Rollup v1.20.0+.

    Install

    Using npm:

    npm install @rollup/plugin-dynamic-import-vars --save-dev

    Usage

    Create a rollup.config.js configuration file and import the plugin:

    import dynamicImportVars from '@rollup/plugin-dynamic-import-vars';
     
    export default {
      plugins: [
        dynamicImportVars({
          // options
        })
      ]
    };

    Options

    include

    Type: String | Array[...String]
    Default: []

    Files to include in this plugin (default all).

    exclude

    Type: String | Array[...String]
    Default: []

    Files to exclude in this plugin (default none).

    warnOnError

    Type: Boolean
    Default: false

    By default, the plugin quits the build process when it encounters an error. If you set this option to true, it will throw a warning instead and leave the code untouched.

    How it works

    When a dynamic import contains a concatenated string, the variables of the string are replaced with a glob pattern. This glob pattern is evaluated during the build, and any files found are added to the rollup bundle. At runtime, the correct import is returned for the full concatenated string.

    Some example patterns and the glob they produce:

    `./locales/${locale}.js` -> './locales/*.js'
    `./${folder}/${name}.js` -> './*/*.js'
    `./module-${name}.js` -> './module-*.js'
    `./modules-${name}/index.js` -> './modules-*/index.js'
    './locales/' + locale + '.js' -> './locales/*.js'
    './locales/' + locale + foo + bar '.js' -> './locales/*.js'
    './locales/' + `${locale}.js` -> './locales/*.js'
    './locales/' + `${foo + bar}.js` -> './locales/*.js'
    './locales/'.concat(locale, '.js') -> './locales/*.js'
    './'.concat(folder, '/').concat(name, '.js') -> './*/*.js'

    Code that looks like this:

    function importLocale(locale) {
      return import(`./locales/${locale}.js`);
    }

    Is turned into:

    function __variableDynamicImportRuntime__(path) {
      switch (path) {
        case './locales/en-GB.js':
          return import('./locales/en-GB.js');
        case './locales/en-US.js':
          return import('./locales/en-US.js');
        case './locales/nl-NL.js':
          return import('./locales/nl-NL.js');
        default:
          throw new Error('Unknown variable dynamic import: ' + path);
      }
    }
     
    function importLocale(locale) {
      return __variableDynamicImportRuntime__(`./locales/${locale}.js`);
    }

    Limitations

    To know what to inject in the rollup bundle, we have to be able to do some static analysis on the code and make some assumptions about the possible imports. For example, if you use just a variable you could in theory import anything from your entire file system.

    function importModule(path) {
      // who knows what will be imported here?
      return import(path);
    }

    To help static analysis, and to avoid possible foot guns, we are limited to a couple of rules:

    Imports must start with ./ or ../.

    All imports must start relative to the importing file. The import should not start with a variable, an absolute path or a bare import:

    // Not allowed
    import(bar);
    import(`${bar}.js`);
    import(`/foo/${bar}.js`);
    import(`some-library/${bar}.js`);

    Imports must end with a file extension

    A folder may contain files you don't intend to import. We, therefore, require imports to end with a file extension in the static parts of the import.

    // Not allowed
    import(`./foo/${bar}`);
    // allowed
    import(`./foo/${bar}.js`);

    Imports to your own directory must specify a filename pattern

    If you import your own directory you likely end up with files you did not intend to import, including your own module. It is therefore required to give a more specific filename pattern:

    // not allowed
    import(`./${foo}.js`);
    // allowed
    import(`./module-${foo}.js`);

    Globs only go one level deep

    When generating globs, each variable in the string is converted to a glob * with a maximum of one star per directory depth. This avoids unintentionally adding files from many directories to your import.

    In the example below this generates ./foo/*/*.js and not ./foo/**/*.js.

    import(`./foo/${x}${y}/${z}.js`);

    Meta

    CONTRIBUTING

    LICENSE (MIT)

    Install

    npm i @rollup/plugin-dynamic-import-vars

    DownloadsWeekly Downloads

    3,772

    Version

    1.1.1

    License

    MIT

    Unpacked Size

    21.2 kB

    Total Files

    6

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