1 files changed, 120 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/workers/parser/mapBindings.js b/devtools/client/debugger/src/workers/parser/mapBindings.js
new file mode 100644
index 0000000000..f8260787f1
--- /dev/null
+++ b/devtools/client/debugger/src/workers/parser/mapBindings.js
@@ -0,0 +1,120 @@
+/* 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/>. */
+
+import { replaceNode } from "./utils/ast";
+import { isTopLevel } from "./utils/helpers";
+
+import generate from "@babel/generator";
+import * as t from "@babel/types";
+
+function getAssignmentTarget(node, bindings) {
+  if (t.isObjectPattern(node)) {
+    for (const property of node.properties) {
+      if (t.isRestElement(property)) {
+        property.argument = getAssignmentTarget(property.argument, bindings);
+      } else {
+        property.value = getAssignmentTarget(property.value, bindings);
+      }
+    }
+
+    return node;
+  }
+
+  if (t.isArrayPattern(node)) {
+    for (const [i, element] of node.elements.entries()) {
+      node.elements[i] = getAssignmentTarget(element, bindings);
+    }
+
+    return node;
+  }
+
+  if (t.isAssignmentPattern(node)) {
+    node.left = getAssignmentTarget(node.left, bindings);
+
+    return node;
+  }
+
+  if (t.isRestElement(node)) {
+    node.argument = getAssignmentTarget(node.argument, bindings);
+
+    return node;
+  }
+
+  if (t.isIdentifier(node)) {
+    return bindings.includes(node.name)
+      ? node
+      : t.memberExpression(t.identifier("self"), node);
+  }
+
+  return node;
+}
+
+// translates new bindings `var a = 3` into `self.a = 3`
+// and existing bindings `var a = 3` into `a = 3` for re-assignments
+function globalizeDeclaration(node, bindings) {
+  return node.declarations.map(declaration =>
+    t.expressionStatement(
+      t.assignmentExpression(
+        "=",
+        getAssignmentTarget(declaration.id, bindings),
+        declaration.init || t.unaryExpression("void", t.numericLiteral(0))
+      )
+    )
+  );
+}
+
+// translates new bindings `a = 3` into `self.a = 3`
+// and keeps assignments the same for existing bindings.
+function globalizeAssignment(node, bindings) {
+  return t.assignmentExpression(
+    node.operator,
+    getAssignmentTarget(node.left, bindings),
+    node.right
+  );
+}
+
+export default function mapExpressionBindings(expression, ast, bindings = []) {
+  let isMapped = false;
+  let shouldUpdate = true;
+
+  t.traverse(ast, (node, ancestors) => {
+    const parent = ancestors[ancestors.length - 1];
+
+    if (t.isWithStatement(node)) {
+      shouldUpdate = false;
+      return;
+    }
+
+    if (!isTopLevel(ancestors)) {
+      return;
+    }
+
+    if (t.isAssignmentExpression(node)) {
+      if (t.isIdentifier(node.left) || t.isPattern(node.left)) {
+        const newNode = globalizeAssignment(node, bindings);
+        isMapped = true;
+        replaceNode(ancestors, newNode);
+        return;
+      }
+
+      return;
+    }
+
+    if (!t.isVariableDeclaration(node)) {
+      return;
+    }
+
+    if (!t.isForStatement(parent.node)) {
+      const newNodes = globalizeDeclaration(node, bindings);
+      isMapped = true;
+      replaceNode(ancestors, newNodes);
+    }
+  });
+
+  if (!shouldUpdate || !isMapped) {
+    return expression;
+  }
+
+  return generate(ast).code;
+}