Suppress missing-require warnings in ES6 extends clauses from externs, e.g. class MyClass extends React.Component (rework of PR 1192 to match rest of class more closely)

Author: supersteves

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

@@ -166,7 +166,7 @@ public void visit(NodeTraversal t, Node n, Node parent) {
         visitNewNode(t, n);
         break;
       case Token.CLASS:
-        visitClassNode(n);
+        visitClassNode(t, n);
         break;
       case Token.IMPORT:
       case Token.EXPORT:
@@ -320,14 +320,32 @@ private void visitNewNode(NodeTraversal t, Node newNode) {
     }
   }
 
-  private void visitClassNode(Node classNode) {
+  private void visitClassNode(NodeTraversal t, Node classNode) {
     String name = NodeUtil.getClassName(classNode);
     if (name != null) {
       constructors.add(name);
     }
+    
     Node extendClass = classNode.getSecondChild();
+    
+    // If the superclass is something other than a qualified name, ignore it.
     if (extendClass.isQualifiedName()) {
-      usages.put(extendClass.getQualifiedName(), extendClass);
+      // Grab the root superclass namespace.
+      Node root = NodeUtil.getRootOfQualifiedName(extendClass);
+      
+      // It should always be a name. Extending this.something or 
+      // super.something is unlikely.
+      // We only consider programmer-defined superclasses that are
+      // global variables, or are defined on global variables.
+      if (root.isName()) {
+        String rootName = root.getString();
+        Var var = t.getScope().getVar(rootName);
+        if (var != null && (var.isLocal() || var.isExtern())) {
+          // "require" not needed for these
+        } else {
+          usages.put(extendClass.getQualifiedName(), extendClass);
+        }
+      }
     }
   }
 

test/com/google/javascript/jscomp/MissingRequireTest.java

@@ -22,6 +22,8 @@
 import com.google.common.collect.ImmutableList;
 import com.google.javascript.jscomp.CompilerOptions.LanguageMode;
 
+import java.util.List;
+
 /**
  * Tests for the "missing requires" check in {@link CheckRequiresForConstructors}.
  *
@@ -140,7 +142,31 @@ public void testFailEs6ClassExtends() {
     String warning = "'goog.foo.Bar.Inner' used but not goog.require'd";
     test(js, js, null, MISSING_REQUIRE_WARNING, warning);
   }
-
+  
+  public void testFailEs6ClassExtendsSomethingWithoutNS() {
+    setAcceptedLanguage(LanguageMode.ECMASCRIPT6);
+    String js = "var goog = {}; class SubClass extends SomethingWithoutNS {}";
+    String warning = "'SomethingWithoutNS' used but not goog.require'd";
+    test(js, js, null, MISSING_REQUIRE_WARNING, warning);
+  }
+  
+  public void testEs6ClassExtendsSomethingInExterns() {
+    setAcceptedLanguage(LanguageMode.ECMASCRIPT6);
+    String js = "var goog = {}; class SubClass extends SomethingInExterns {}";
+    List<SourceFile> externs = ImmutableList.of(SourceFile.fromCode("externs", 
+        "/** @constructor */ var SomethingInExterns;")); 
+    test(externs, js, js, null, null, null);
+  }
+  
+  public void testEs6ClassExtendsSomethingInExternsWithNS() {
+    setAcceptedLanguage(LanguageMode.ECMASCRIPT6);
+    String js = "var goog = {}; class SubClass extends MyExterns.SomethingInExterns {}";
+    List<SourceFile> externs = ImmutableList.of(SourceFile.fromCode("externs", 
+        "var MyExterns;\n"
+        + "/** @constructor */ MyExterns.SomethingInExterns;")); 
+    test(externs, js, js, null, null, null);
+  }
+  
   public void testFailWithNestedNewNodes() {
     String[] js =
         new String[] {"var goog = {}; goog.require('goog.foo.Bar'); "