Add support for transpilation of computed fields in RewriteClassMembers.

This change stops throwing errors when encountering computed fields in classes and properly transpiles them into assignments inside the constructor for non-static public fields or class property assignments below the class for static fields.

PiperOrigin-RevId: 553629460

Author: Closure Team

src/com/google/javascript/jscomp/NodeTraversal.java

@@ -651,6 +651,7 @@ private void traverseAtScope(AbstractScope<?, ?> s) {
         }
         break;
       case BLOCK:
+      case SWITCH:
         if (callback.shouldTraverse(this, n, null)) {
           pushScope(s);
 
@@ -700,16 +701,6 @@ private void traverseAtScope(AbstractScope<?, ?> s) {
           callback.visit(this, n, null);
         }
         break;
-      case SWITCH:
-        if (callback.shouldTraverse(this, n, null)) {
-          pushScope(s);
-
-          traverseChildren(n);
-
-          popScope();
-          callback.visit(this, n, null);
-        }
-        break;
       default:
         checkState(
             s.isGlobal() || s.isModuleScope(), "Expected global or module scope. Got: (%s)", s);
@@ -1303,6 +1294,7 @@ private static boolean isHoistScopeRootNode(Node n) {
           }
           return rootNode;
         case MEMBER_FIELD_DEF:
+        case COMPUTED_FIELD_DEF:
         case CLASS:
         case MODULE_BODY:
         case ROOT:

src/com/google/javascript/jscomp/RewriteClassMembers.java

@@ -89,10 +89,16 @@ public boolean shouldTraverse(NodeTraversal t, Node n, Node parent) {
         classStack.push(new ClassRecord(n, classNameNode.getQualifiedName(), classInsertionPoint));
         break;
       case COMPUTED_FIELD_DEF:
+        if (NodeUtil.canBeSideEffected(n.getFirstChild())) {
+          t.report(
+              n,
+              TranspilationUtil.CANNOT_CONVERT_YET,
+              "Class contains computed field with possible side effects");
+          return false;
+        }
         checkState(!classStack.isEmpty());
-        t.report(n, TranspilationUtil.CANNOT_CONVERT_YET, "Computed fields");
-        classStack.peek().cannotConvert = true;
-        return false;
+        classStack.peek().enterField(n);
+        break;
       case MEMBER_FIELD_DEF:
         checkState(!classStack.isEmpty());
         classStack.peek().enterField(n);
@@ -145,12 +151,14 @@ public void visit(NodeTraversal t, Node n, Node parent) {
       case CLASS:
         visitClass(t);
         return;
+      case COMPUTED_FIELD_DEF:
       case MEMBER_FIELD_DEF:
         classStack.peek().exitField();
         return;
       case THIS:
         Node rootNode = t.getClosestScopeRootNodeBindingThisOrSuper();
-        if (rootNode.isMemberFieldDef() && rootNode.isStaticMember()) {
+        if (rootNode.isStaticMember()
+            && (rootNode.isMemberFieldDef() || rootNode.isComputedFieldDef())) {
           Node className = rootNode.getGrandparent().getFirstChild().cloneNode();
           n.replaceWith(className);
           t.reportCodeChange(className);
@@ -195,7 +203,8 @@ private void rewriteInstanceMembers(NodeTraversal t, ClassRecord record) {
 
     while (!instanceMembers.isEmpty()) {
       Node instanceMember = instanceMembers.pop();
-      checkState(instanceMember.isMemberFieldDef());
+      checkState(
+          instanceMember.isMemberFieldDef() || instanceMember.isComputedFieldDef(), instanceMember);
 
       for (Node nameInRhs : record.referencedNamesByMember.get(instanceMember)) {
         String name = nameInRhs.getString();
@@ -209,8 +218,10 @@ private void rewriteInstanceMembers(NodeTraversal t, ClassRecord record) {
       }
 
       Node thisNode = astFactory.createThisForEs6ClassMember(instanceMember);
-
-      Node transpiledNode = convNonCompFieldToGetProp(thisNode, instanceMember.detach());
+      Node transpiledNode =
+          instanceMember.isMemberFieldDef()
+              ? convNonCompFieldToGetProp(thisNode, instanceMember.detach())
+              : convCompFieldToGetElem(thisNode, instanceMember.detach());
       if (insertionPoint == ctorBlock) { // insert the field at the beginning of the block, no super
         ctorBlock.addChildToFront(transpiledNode);
       } else {
@@ -244,6 +255,9 @@ private void rewriteStaticMembers(NodeTraversal t, ClassRecord record) {
         case MEMBER_FIELD_DEF:
           transpiledNode = convNonCompFieldToGetProp(nameToUse, staticMember.detach());
           break;
+        case COMPUTED_FIELD_DEF:
+          transpiledNode = convCompFieldToGetElem(nameToUse, staticMember.detach());
+          break;
         default:
           throw new IllegalStateException(String.valueOf(staticMember));
       }
@@ -272,6 +286,24 @@ private Node convNonCompFieldToGetProp(Node receiver, Node noncomputedField) {
     return result;
   }
 
+  /**
+   * Creates a node that represents receiver[key] = value; where the key and value comes from the
+   * computed field
+   */
+  private Node convCompFieldToGetElem(Node receiver, Node computedField) {
+    checkArgument(computedField.isComputedFieldDef(), computedField);
+    checkArgument(computedField.getParent() == null, computedField);
+    checkArgument(receiver.getParent() == null, receiver);
+    Node getElem = astFactory.createGetElem(receiver, computedField.getFirstChild().detach());
+    Node fieldValue = computedField.getLastChild();
+    Node result =
+        (fieldValue != null)
+            ? astFactory.createAssignStatement(getElem, fieldValue.detach())
+            : astFactory.exprResult(getElem);
+    result.srcrefTreeIfMissing(computedField);
+    return result;
+  }
+
   /**
    * Finds the location in the constructor to put the transpiled instance fields
    *
@@ -378,7 +410,8 @@ void potentiallyRecordNameInRhs(Node nameNode) {
       if (currentMember == null) {
         return;
       }
-      checkState(currentMember.isMemberFieldDef());
+      checkState(
+          currentMember.isMemberFieldDef() || currentMember.isComputedFieldDef(), currentMember);
       referencedNamesByMember.put(currentMember, nameNode);
     }