@rollup/plugin-dynamic-import-vars/dist/es/index.js

Resolving dynamic imports that contain variables.

import path from 'path';
import { walk } from 'estree-walker';
import MagicString from 'magic-string';
import fastGlob from 'fast-glob';
import { generate } from 'astring';
import { createFilter } from '@rollup/pluginutils';

class VariableDynamicImportError extends Error {}

/* eslint-disable-next-line no-template-curly-in-string */
const example = 'For example: import(`./foo/${bar}.js`).';

function sanitizeString(str) {
  if (str === '') return str;
  if (str.includes('*')) {
    throw new VariableDynamicImportError('A dynamic import cannot contain * characters.');
  }
  return fastGlob.escapePath(str);
}

function templateLiteralToGlob(node) {
  let glob = '';

  for (let i = 0; i < node.quasis.length; i += 1) {
    glob += sanitizeString(node.quasis[i].value.raw);
    if (node.expressions[i]) {
      glob += expressionToGlob(node.expressions[i]);
    }
  }

  return glob;
}

function callExpressionToGlob(node) {
  const { callee } = node;
  if (
    callee.type === 'MemberExpression' &&
    callee.property.type === 'Identifier' &&
    callee.property.name === 'concat'
  ) {
    return `${expressionToGlob(callee.object)}${node.arguments.map(expressionToGlob).join('')}`;
  }
  return '*';
}

function binaryExpressionToGlob(node) {
  if (node.operator !== '+') {
    throw new VariableDynamicImportError(`${node.operator} operator is not supported.`);
  }

  return `${expressionToGlob(node.left)}${expressionToGlob(node.right)}`;
}

function expressionToGlob(node) {
  switch (node.type) {
    case 'TemplateLiteral':
      return templateLiteralToGlob(node);
    case 'CallExpression':
      return callExpressionToGlob(node);
    case 'BinaryExpression':
      return binaryExpressionToGlob(node);
    case 'Literal': {
      return sanitizeString(node.value);
    }
    default:
      return '*';
  }
}

const defaultProtocol = 'file:';
const ignoredProtocols = ['data:', 'http:', 'https:'];

function shouldIgnore(glob) {
  const containsAsterisk = glob.includes('*');

  const globURL = new URL(glob, defaultProtocol);

  const containsIgnoredProtocol = ignoredProtocols.some(
    (ignoredProtocol) => ignoredProtocol === globURL.protocol
  );

  return !containsAsterisk || containsIgnoredProtocol;
}

function dynamicImportToGlob(node, sourceString) {
  let glob = expressionToGlob(node);

  if (shouldIgnore(glob)) {
    return null;
  }

  glob = glob.replace(/\*\*/g, '*');

  if (glob.startsWith('*')) {
    throw new VariableDynamicImportError(
      `invalid import "${sourceString}". It cannot be statically analyzed. Variable dynamic imports must start with ./ and be limited to a specific directory. ${example}`
    );
  }

  if (glob.startsWith('/')) {
    throw new VariableDynamicImportError(
      `invalid import "${sourceString}". Variable absolute imports are not supported, imports must start with ./ in the static part of the import. ${example}`
    );
  }

  if (!glob.startsWith('./') && !glob.startsWith('../')) {
    throw new VariableDynamicImportError(
      `invalid import "${sourceString}". Variable bare imports are not supported, imports must start with ./ in the static part of the import. ${example}`
    );
  }

  // Disallow ./*.ext
  const ownDirectoryStarExtension = /^\.\/\*\.\w+$/;
  if (ownDirectoryStarExtension.test(glob)) {
    throw new VariableDynamicImportError(
      `${
        `invalid import "${sourceString}". Variable imports cannot import their own directory, ` +
        'place imports in a separate directory or make the import filename more specific. '
      }${example}`
    );
  }

  if (path.extname(glob) === '') {
    throw new VariableDynamicImportError(
      `invalid import "${sourceString}". A file extension must be included in the static part of the import. ${example}`
    );
  }

  return glob;
}

function dynamicImportVariables({ include, exclude, warnOnError, errorWhenNoFilesFound } = {}) {
  const filter = createFilter(include, exclude);

  return {
    name: 'rollup-plugin-dynamic-import-variables',

    transform(code, id) {
      if (!filter(id)) {
        return null;
      }

      const parsed = this.parse(code);

      let dynamicImportIndex = -1;
      let ms;

      walk(parsed, {
        enter: (node) => {
          if (node.type !== 'ImportExpression') {
            return;
          }
          dynamicImportIndex += 1;

          let importArg;
          if (node.arguments && node.arguments.length > 0) {
            // stringify the argument node, without indents, removing newlines and using single quote strings
            importArg = generate(node.arguments[0], { indent: '' })
              .replace(/\n/g, '')
              .replace(/"/g, "'");
          }

          try {
            // see if this is a variable dynamic import, and generate a glob expression
            const glob = dynamicImportToGlob(node.source, code.substring(node.start, node.end));

            if (!glob) {
              // this was not a variable dynamic import
              return;
            }

            // execute the glob
            const result = fastGlob.sync(glob, { cwd: path.dirname(id) });
            const paths = result.map((r) =>
              r.startsWith('./') || r.startsWith('../') ? r : `./${r}`
            );

            if (errorWhenNoFilesFound && paths.length === 0) {
              const error = new Error(
                `No files found in ${glob} when trying to dynamically load concatted string from ${id}`
              );
              if (warnOnError) {
                this.warn(error);
              } else {
                this.error(error);
              }
            }

            // create magic string if it wasn't created already
            ms = ms || new MagicString(code);
            // unpack variable dynamic import into a function with import statements per file, rollup
            // will turn these into chunks automatically
            ms.prepend(
              `function __variableDynamicImportRuntime${dynamicImportIndex}__(path) {
  switch (path) {
${paths
  .map((p) => `    case '${p}': return import('${p}'${importArg ? `, ${importArg}` : ''});`)
  .join('\n')}
${`    default: return new Promise(function(resolve, reject) {
      (typeof queueMicrotask === 'function' ? queueMicrotask : setTimeout)(
        reject.bind(null, new Error("Unknown variable dynamic import: " + path))
      );
    })\n`}   }
 }\n\n`
            );

            // call the runtime function instead of doing a dynamic import, the import specifier will
            // be evaluated at runtime and the correct import will be returned by the injected function
            ms.overwrite(
              node.start,
              node.start + 6,
              `__variableDynamicImportRuntime${dynamicImportIndex}__`
            );
          } catch (error) {
            if (error instanceof VariableDynamicImportError) {
              // TODO: line number
              if (warnOnError) {
                this.warn(error);
              } else {
                this.error(error);
              }
            } else {
              this.error(error);
            }
          }
        }
      });

      if (ms && dynamicImportIndex !== -1) {
        return {
          code: ms.toString(),
          map: ms.generateMap({
            file: id,
            includeContent: true,
            hires: true
          })
        };
      }
      return null;
    }
  };
}

export { VariableDynamicImportError, dynamicImportVariables as default, dynamicImportToGlob };
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