1 files changed, 147 insertions, 0 deletions
diff --git a/tools/esmify/static-import.js b/tools/esmify/static-import.js
new file mode 100644
index 0000000000..e99bfb3380
--- /dev/null
+++ b/tools/esmify/static-import.js
@@ -0,0 +1,147 @@
+/* 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/. */
+
+/* eslint-env node */
+
+const _path = require("path");
+const { getESMFiles } = require(_path.resolve(__dirname, "./is-esmified.js"));
+const {
+  esmifyExtension,
+  isString,
+  warnForPath,
+  isMemberExpressionWithIdentifiers,
+} = require(_path.resolve(__dirname, "./utils.js"));
+
+function isTargetESM(resourceURI) {
+  if ("ESMIFY_TARGET_PREFIX" in process.env) {
+    const files = getESMFiles(resourceURI);
+    const targetPrefix = process.env.ESMIFY_TARGET_PREFIX;
+    for (const esm of files) {
+      if (esm.startsWith(targetPrefix)) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  return true;
+}
+
+function isImportESModuleCall(node) {
+  return isMemberExpressionWithIdentifiers(node.callee, [
+    "ChromeUtils",
+    "importESModule",
+  ]);
+}
+
+// Replace `ChromeUtils.import`, `Cu.import`, and `ChromeUtils.importESModule`
+// with static import if it's at the top-level of system ESM file.
+function tryReplacingWithStaticImport(
+  jscodeshift,
+  inputFile,
+  path,
+  resourceURINode,
+  alwaysReplace
+) {
+  if (!alwaysReplace && !inputFile.endsWith(".sys.mjs")) {
+    // Static import is available only in system ESM.
+    return false;
+  }
+
+  // Check if it's at the top-level.
+  if (path.parent.node.type !== "VariableDeclarator") {
+    return false;
+  }
+
+  if (path.parent.parent.node.type !== "VariableDeclaration") {
+    return false;
+  }
+
+  const decls = path.parent.parent.node;
+  if (decls.declarations.length !== 1) {
+    return false;
+  }
+
+  if (path.parent.parent.parent.node.type !== "Program") {
+    return false;
+  }
+
+  if (path.node.arguments.length !== 1) {
+    return false;
+  }
+
+  const resourceURI = resourceURINode.value;
+
+  // Collect imported symbols.
+  const specs = [];
+  if (path.parent.node.id.type === "Identifier") {
+    specs.push(jscodeshift.importNamespaceSpecifier(path.parent.node.id));
+  } else if (path.parent.node.id.type === "ObjectPattern") {
+    for (const prop of path.parent.node.id.properties) {
+      if (prop.shorthand) {
+        specs.push(jscodeshift.importSpecifier(prop.key));
+      } else if (prop.value.type === "Identifier") {
+        specs.push(jscodeshift.importSpecifier(prop.key, prop.value));
+      } else {
+        return false;
+      }
+    }
+  } else {
+    return false;
+  }
+
+  // If this is `ChromeUtils.import` or `Cu.import`, replace the extension.
+  // no-op for `ChromeUtils.importESModule`.
+  resourceURINode.value = esmifyExtension(resourceURI);
+
+  const e = jscodeshift.importDeclaration(specs, resourceURINode);
+  e.comments = path.parent.parent.node.comments;
+  path.parent.parent.node.comments = [];
+  path.parent.parent.replace(e);
+
+  return true;
+}
+
+function replaceImportESModuleCall(
+  inputFile,
+  jscodeshift,
+  path,
+  alwaysReplace
+) {
+  if (path.node.arguments.length !== 1) {
+    warnForPath(
+      inputFile,
+      path,
+      `importESModule call should have only one argument`
+    );
+    return;
+  }
+
+  const resourceURINode = path.node.arguments[0];
+  if (!isString(resourceURINode)) {
+    warnForPath(inputFile, path, `resource URI should be a string`);
+    return;
+  }
+
+  if (!alwaysReplace) {
+    const resourceURI = resourceURINode.value;
+    if (!isTargetESM(resourceURI)) {
+      return;
+    }
+  }
+
+  // If this cannot be replaced with static import, do nothing.
+  tryReplacingWithStaticImport(
+    jscodeshift,
+    inputFile,
+    path,
+    resourceURINode,
+    alwaysReplace
+  );
+}
+
+exports.isImportESModuleCall = isImportESModuleCall;
+exports.tryReplacingWithStaticImport = tryReplacingWithStaticImport;
+exports.replaceImportESModuleCall = replaceImportESModuleCall;