1 files changed, 165 insertions, 0 deletions
diff --git a/tools/esmify/utils.js b/tools/esmify/utils.js
new file mode 100644
index 0000000000..801aab62af
--- /dev/null
+++ b/tools/esmify/utils.js
@@ -0,0 +1,165 @@
+/* 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/. */
+
+// Shared utility functions.
+
+/* eslint-env node */
+
+function warnForPath(inputFile, path, message) {
+  const loc = path.node.loc;
+  console.log(
+    `WARNING: ${inputFile}:${loc.start.line}:${loc.start.column} : ${message}`
+  );
+}
+
+// Get the previous statement of `path.node` in `Program`.
+function getPrevStatement(path) {
+  const parent = path.parent;
+  if (parent.node.type !== "Program") {
+    return null;
+  }
+
+  const index = parent.node.body.findIndex(n => n == path.node);
+  if (index === -1) {
+    return null;
+  }
+
+  if (index === 0) {
+    return null;
+  }
+
+  return parent.node.body[index - 1];
+}
+
+// Get the next statement of `path.node` in `Program`.
+function getNextStatement(path) {
+  const parent = path.parent;
+  if (parent.node.type !== "Program") {
+    return null;
+  }
+
+  const index = parent.node.body.findIndex(n => n == path.node);
+  if (index === -1) {
+    return null;
+  }
+
+  if (index + 1 == parent.node.body.length) {
+    return null;
+  }
+
+  return parent.node.body[index + 1];
+}
+
+function isIdentifier(node, name) {
+  if (node.type !== "Identifier") {
+    return false;
+  }
+  if (node.name !== name) {
+    return false;
+  }
+  return true;
+}
+
+function isString(node) {
+  return node.type === "Literal" && typeof node.value === "string";
+}
+
+const jsmExtPattern = /\.(jsm|js|jsm\.js)$/;
+
+function esmifyExtension(path) {
+  return path.replace(jsmExtPattern, ".sys.mjs");
+}
+
+// Given possible member expression, return the list of Identifier nodes in
+// the source order.
+//
+// Returns an empty array if:
+//   * not a simple MemberExpression tree with Identifiers
+//   * there's computed property
+function memberExpressionsToIdentifiers(memberExpr) {
+  let ids = [];
+
+  function f(node) {
+    if (node.type !== "MemberExpression" || node.computed) {
+      return false;
+    }
+
+    if (node.object.type === "Identifier") {
+      ids.push(node.object);
+      ids.push(node.property);
+      return true;
+    }
+
+    if (!f(node.object)) {
+      return false;
+    }
+    ids.push(node.property);
+    return true;
+  }
+
+  if (!f(memberExpr)) {
+    return [];
+  }
+
+  return ids;
+}
+
+// Returns true if the node is a simple MemberExpression tree with Identifiers
+// matches expectedIDs.
+function isMemberExpressionWithIdentifiers(node, expectedIDs) {
+  const actualIDs = memberExpressionsToIdentifiers(node);
+  if (actualIDs.length !== expectedIDs.length) {
+    return false;
+  }
+
+  for (let i = 0; i < expectedIDs.length; i++) {
+    if (actualIDs[i].name !== expectedIDs[i]) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Rewrite the Identifiers of MemberExpression tree to toIDs.
+// `node` must be a simple MemberExpression tree with Identifiers, and
+// the length of Identifiers should match.
+function rewriteMemberExpressionWithIdentifiers(node, toIDs) {
+  const actualIDs = memberExpressionsToIdentifiers(node);
+  for (let i = 0; i < toIDs.length; i++) {
+    actualIDs[i].name = toIDs[i];
+  }
+}
+
+// Create a simple MemberExpression tree with given Identifiers.
+function createMemberExpressionWithIdentifiers(jscodeshift, ids) {
+  if (ids.length < 2) {
+    throw new Error("Unexpected length of ids for member expression");
+  }
+
+  if (ids.length > 2) {
+    return jscodeshift.memberExpression(
+      createMemberExpressionWithIdentifiers(jscodeshift, ids.slice(0, -1)),
+      jscodeshift.identifier(ids[ids.length - 1])
+    );
+  }
+
+  return jscodeshift.memberExpression(
+    jscodeshift.identifier(ids[0]),
+    jscodeshift.identifier(ids[1])
+  );
+}
+
+exports.warnForPath = warnForPath;
+exports.getPrevStatement = getPrevStatement;
+exports.getNextStatement = getNextStatement;
+exports.isIdentifier = isIdentifier;
+exports.isString = isString;
+exports.jsmExtPattern = jsmExtPattern;
+exports.esmifyExtension = esmifyExtension;
+exports.isMemberExpressionWithIdentifiers = isMemberExpressionWithIdentifiers;
+exports.rewriteMemberExpressionWithIdentifiers =
+  rewriteMemberExpressionWithIdentifiers;
+exports.createMemberExpressionWithIdentifiers =
+  createMemberExpressionWithIdentifiers;