[api] Add documentation for various HasProperty functions.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index edba8eaece01ae12955c89426ef8c57edf7a973d..ba71ee8924b9fec4f1ce5efb7f966f91967f65cd 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -2968,6 +2968,21 @@ class V8_EXPORT Object : public Value {
       Local<Context> context, Local<String> key);
 
   V8_DEPRECATE_SOON("Use maybe version", bool Has(Local<Value> key));
+  /**
+   * Object::Has() calls the abstract operation HasProperty(O, P) described
+   * in ECMA-262, 7.3.10. Has() returns
+   * true, if the object has the property, either own or on the prototype chain.
+   * Interceptors, i.e., PropertyQueryCallbacks, are called if present.
+   *
+   * Has() has the same side effects as JavaScript's `variable in object`.
+   * For example, calling Has() on a revoked proxy will throw an exception.
+   *
+   * \note Has() converts the key to a name, which possibly calls back into
+   * JavaScript.
+   *
+   * See also v8::Object::HasOwnProperty() and
+   * v8::Object::HasRealNamedProperty().
+   */
   V8_WARN_UNUSED_RESULT Maybe<bool> Has(Local<Context> context,
                                         Local<Value> key);
 
@@ -3132,12 +3147,31 @@ class V8_EXPORT Object : public Value {
 
   // Testers for local properties.
   V8_DEPRECATED("Use maybe version", bool HasOwnProperty(Local<String> key));
+
+  /**
+   * HasOwnProperty() is like JavaScript's Object.prototype.hasOwnProperty().
+   *
+   * See also v8::Object::Has() and v8::Object::HasRealNamedProperty().
+   */
   V8_WARN_UNUSED_RESULT Maybe<bool> HasOwnProperty(Local<Context> context,
                                                    Local<Name> key);
   V8_WARN_UNUSED_RESULT Maybe<bool> HasOwnProperty(Local<Context> context,
                                                    uint32_t index);
   V8_DEPRECATE_SOON("Use maybe version",
                     bool HasRealNamedProperty(Local<String> key));
+  /**
+   * Use HasRealNamedProperty() if you want to check if an object has an own
+   * property without causing side effects, i.e., without calling interceptors.
+   *
+   * This function is similar to v8::Object::HasOwnProperty(), but it does not
+   * call interceptors.
+   *
+   * \note Consider using non-masking interceptors, i.e., the interceptors are
+   * not called if the receiver has the real named property. See
+   * `v8::PropertyHandlerFlags::kNonMasking`.
+   *
+   * See also v8::Object::Has().
+   */
   V8_WARN_UNUSED_RESULT Maybe<bool> HasRealNamedProperty(Local<Context> context,
                                                          Local<Name> key);
   V8_DEPRECATE_SOON("Use maybe version",
@@ -5126,16 +5160,31 @@ class V8_EXPORT FunctionTemplate : public Template {
   friend class ObjectTemplate;
 };
 
+/**
+ * Configuration flags for v8::NamedPropertyHandlerConfiguration or
+ * v8::IndexedPropertyHandlerConfiguration.
+ */
 enum class PropertyHandlerFlags {
+  /**
+   * None.
+   */
   kNone = 0,
-  // See ALL_CAN_READ above.
+
+  /**
+   * See ALL_CAN_READ above.
+   */
   kAllCanRead = 1,
-  // Will not call into interceptor for properties on the receiver or prototype
-  // chain, i.e., only call into interceptor for properties that do not exist.
-  // Currently only valid for named interceptors.
+
+  /** Will not call into interceptor for properties on the receiver or prototype
+   * chain, i.e., only call into interceptor for properties that do not exist.
+   * Currently only valid for named interceptors.
+   */
   kNonMasking = 1 << 1,
-  // Will not call into interceptor for symbol lookup.  Only meaningful for
-  // named interceptors.
+
+  /**
+   * Will not call into interceptor for symbol lookup.  Only meaningful for
+   * named interceptors.
+   */
   kOnlyInterceptStrings = 1 << 2,
 };