Don't collapse properties on objects called with hasOwnProperty

If we see a call like "a.b.hasOwnProperty(c);", treat it the same (in CollapseProperties) as a.b[c]. This fixes a bug where the compiler collapsed properties on objects that were only used through hasOwnProperty.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=184861876

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

@@ -424,6 +424,13 @@ public void collect(JSModule module, Scope scope, Node n) {
           }
           name = n.getQualifiedName();
           break;
+        case CALL:
+          if (isObjectHasOwnPropertyCall(n)) {
+            String qname = n.getFirstFirstChild().getQualifiedName();
+            Name globalName = getOrCreateName(qname, true);
+            globalName.usedHasOwnProperty = true;
+          }
+          return;
         default:
           return;
       }
@@ -828,6 +835,23 @@ private boolean isClassDefiningCall(Node callNode) {
       return className != null;
     }
 
+    /** Detect calls of the form a.b.hasOwnProperty(c); that prevent property collapsing on a.b */
+    private boolean isObjectHasOwnPropertyCall(Node callNode) {
+      checkArgument(callNode.isCall(), callNode);
+      if (!callNode.hasTwoChildren()) {
+        return false;
+      }
+      Node fn = callNode.getFirstChild();
+      if (!fn.isGetProp()) {
+        return false;
+      }
+      Node callee = fn.getFirstChild();
+      Node method = fn.getSecondChild();
+      return method.isString()
+          && "hasOwnProperty".equals(method.getString())
+          && callee.isQualifiedName();
+    }
+
     /**
      * Determines whether the result of a hook (x?y:z) or boolean expression
      * (x||y) or (x&&y) is assigned to a specific global name.
@@ -1019,6 +1043,7 @@ enum Type {
     private boolean declaredType = false;
     private boolean isDeclared = false;
     private boolean isModuleProp = false;
+    private boolean usedHasOwnProperty = false;
     int globalSets = 0;
     int localSets = 0;
     int localSetsWithNoCollapse = 0;
@@ -1297,6 +1322,10 @@ boolean canCollapseUnannotatedChildNames() {
         return false;
       }
 
+      if (usedHasOwnProperty) {
+        return false;
+      }
+
       if (declaredType) {
         return true;
       }

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

@@ -1172,6 +1172,46 @@ public void testBug1974371() {
             + "for (var key in Foo) {}");
   }
 
+  public void testHasOwnProperty() {
+    testSame("var a = {b: 3}; if (a.hasOwnProperty(foo)) { alert('ok'); }");
+    testSame("var a = {b: 3}; if (a.hasOwnProperty(foo)) { alert('ok'); } a.b;");
+  }
+
+  public void testHasOwnPropertyOnNonGlobalName() {
+    testSame(lines(
+        "/** @constructor */",
+        "function A() {",
+        "  this.foo = {a: 1, b: 1};",
+        "}",
+        "A.prototype.bar = function(prop) {",
+        "  return this.foo.hasOwnProperty(prop);",
+        "}"));
+    testSame("var a = {'b': {'c': 1}}; a['b'].hasOwnProperty('c');");
+    testSame("var a = {b: 3}; if (Object.prototype.hasOwnProperty.call(a, 'b')) { alert('ok'); }");
+  }
+
+  public void testHasOwnPropertyNested() {
+    test(
+        "var a = {b: {c: 3}}; if (a.b.hasOwnProperty('c')) { alert('ok'); }",
+        "var a$b =   {c: 3};  if (a$b.hasOwnProperty('c')) { alert('ok'); }");
+    test(
+        "var a = {b: {c: 3}}; if (a.b.hasOwnProperty('c')) { alert('ok'); } a.b.c;",
+        "var a$b =   {c: 3};  if (a$b.hasOwnProperty('c')) { alert('ok'); } a$b.c;");
+    test("var a = {}; a.b = function(p) { log(a.b.c.hasOwnProperty(p)); }; a.b.c = {};",
+        "var a$b = function(p) { log(a$b$c.hasOwnProperty(p)); }; var a$b$c = {};");
+}
+
+  public void testHasOwnPropertyMultiple() {
+    testSame("var a = {b: 3, c: 4, d: 5}; if (a.hasOwnProperty(prop)) { alert('ok'); }");
+  }
+
+  public void testObjectStaticMethodsPreventCollapsing() {
+    testSame("var a = {b: 3}; alert(Object.getOwnPropertyDescriptor(a, 'b'));");
+    testSame("var a = {b: 3}; alert(Object.getOwnPropertyDescriptors(a));");
+    testSame("var a = {b: 3}; alert(Object.getOwnPropertyNames(a));");
+    testSame("var a = {b: 3, [Symbol('c')]: 4}; alert(Object.getOwnPropertySymbols(a));");
+  }
+
   private static final String COMMON_ENUM =
         "/** @enum {Object} */ var Foo = {A: {c: 2}, B: {c: 3}};";
 

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

@@ -156,6 +156,12 @@ public void testObjLitAssignmentDepth4() {
          "var a$b$c$d$e = 1; var a$b$c$d$f = 2; var g = null; use(a$b$c$d$e);");
   }
 
+  public void testHasOwnProperty() {
+    test(
+        "var a = {'b': 1, 'c': 1}; var alias = a;    alert(alias.hasOwnProperty('c'));",
+        "var a = {'b': 1, 'c': 1}; var alias = null; alert(a.hasOwnProperty('c'));");
+  }
+
   public void testAliasCreatedForObjectDepth1_1() {
     // An object's properties are not collapsed if the object is referenced
     // in a such a way that an alias is created for it, if that alias is used.