gecko-dev/tools/esmify/use-import-export-declarations.js

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// jscodeshift rule to replace EXPORTED_SYMBOLS with export declarations,
// and also convert existing ChromeUtils.importESModule to static import.

/* eslint-env node */

const _path = require("path");
const {
  warnForPath,
  getPrevStatement,
  getNextStatement,
} = require(_path.resolve(__dirname, "./utils.js"));
const {
  isImportESModuleCall,
  replaceImportESModuleCall,
} = require(_path.resolve(__dirname, "./static-import.js"));

module.exports = function (fileInfo, api) {
  const { jscodeshift } = api;
  const root = jscodeshift(fileInfo.source);
  doTranslate(fileInfo.path, jscodeshift, root);
  return root.toSource({ lineTerminator: "\n" });
};

module.exports.doTranslate = doTranslate;

// Move the comment for `path.node` to adjacent statement, keeping the position
// as much as possible.
function moveComments(inputFile, path) {
  const next = getNextStatement(path);
  if (next) {
    if (next.comments) {
      next.comments = [...path.node.comments, ...next.comments];
    } else {
      next.comments = path.node.comments;
    }
    path.node.comments = [];

    return;
  }

  const prev = getPrevStatement(path);
  if (prev) {
    path.node.comments.forEach(c => {
      c.leading = false;
      c.trailing = true;
    });

    if (prev.comments) {
      prev.comments = [...prev.comments, ...path.node.comments];
    } else {
      prev.comments = path.node.comments;
    }
    path.node.comments = [];

    return;
  }

  warnForPath(
    inputFile,
    path,
    `EXPORTED_SYMBOLS has comments and it cannot be preserved`
  );
}

function collectAndRemoveExportedSymbols(inputFile, root) {
  const nodes = root.findVariableDeclarators("EXPORTED_SYMBOLS");
  if (!nodes.length) {
    throw Error(`EXPORTED_SYMBOLS not found`);
  }

  let path = nodes.get(0);
  const obj = nodes.get(0).node.init;
  if (!obj) {
    throw Error(`EXPORTED_SYMBOLS is not statically known`);
  }

  if (path.parent.node.declarations.length !== 1) {
    throw Error(`EXPORTED_SYMBOLS shouldn't be declared with other variables`);
  }

  if (path.parent.node.comments && path.parent.node.comments.length) {
    moveComments(inputFile, path.parent);
  }

  path.parent.prune();

  const EXPORTED_SYMBOLS = new Set();
  if (obj.type !== "ArrayExpression") {
    throw Error(`EXPORTED_SYMBOLS is not statically known`);
  }

  for (const elem of obj.elements) {
    if (elem.type !== "Literal") {
      throw Error(`EXPORTED_SYMBOLS is not statically known`);
    }
    var name = elem.value;
    if (typeof name !== "string") {
      throw Error(`EXPORTED_SYMBOLS item must be a string`);
    }
    EXPORTED_SYMBOLS.add(name);
  }

  return EXPORTED_SYMBOLS;
}

function isTopLevel(path) {
  return path.parent.node.type === "Program";
}

function convertToExport(jscodeshift, path, name) {
  const e = jscodeshift.exportNamedDeclaration(path.node);
  e.comments = [];
  e.comments = path.node.comments;
  path.node.comments = [];

  path.replace(e);
}

function doTranslate(inputFile, jscodeshift, root) {
  const EXPORTED_SYMBOLS = collectAndRemoveExportedSymbols(inputFile, root);

  root.find(jscodeshift.FunctionDeclaration).forEach(path => {
    if (!isTopLevel(path)) {
      return;
    }
    const name = path.node.id.name;
    if (!EXPORTED_SYMBOLS.has(name)) {
      return;
    }
    EXPORTED_SYMBOLS.delete(name);
    convertToExport(jscodeshift, path, name);
  });

  root.find(jscodeshift.ClassDeclaration).forEach(path => {
    if (!isTopLevel(path)) {
      return;
    }
    const name = path.node.id.name;
    if (!EXPORTED_SYMBOLS.has(name)) {
      return;
    }
    EXPORTED_SYMBOLS.delete(name);
    convertToExport(jscodeshift, path, name);
  });

  root.find(jscodeshift.VariableDeclaration).forEach(path => {
    if (!isTopLevel(path)) {
      return;
    }

    let exists = false;
    let name;
    for (const decl of path.node.declarations) {
      if (decl.id.type === "Identifier") {
        name = decl.id.name;
        if (EXPORTED_SYMBOLS.has(name)) {
          exists = true;
          break;
        }
      }

      if (decl.id.type === "ObjectPattern") {
        if (decl.id.properties.length === 1) {
          const prop = decl.id.properties[0];
          if (prop.shorthand) {
            if (prop.key.type === "Identifier") {
              name = prop.key.name;
              if (EXPORTED_SYMBOLS.has(name)) {
                exists = true;
                break;
              }
            }
          }
        }
      }
    }
    if (!exists) {
      return;
    }

    if (path.node.declarations.length !== 1) {
      throw Error(
        `exported variable shouldn't be declared with other variables`
      );
    }

    EXPORTED_SYMBOLS.delete(name);
    convertToExport(jscodeshift, path, name);
  });

  if (EXPORTED_SYMBOLS.size !== 0) {
    throw Error(
      `exported symbols ${[...EXPORTED_SYMBOLS].join(", ")} not found`
    );
  }

  root.find(jscodeshift.CallExpression).forEach(path => {
    if (isImportESModuleCall(path.node)) {
      // This file is not yet renamed. Skip the extension check.
      // Also skip the isTargetESM.
      replaceImportESModuleCall(inputFile, jscodeshift, path, true);
    }
  });
}