Lazily resolve features for proto2 and proto3 for compatibility with old open source gencode that does not invoke feature resolution from gencode static init. (#16907)

PiperOrigin-RevId: 634804242

Author: zhangskz

java/core/src/main/java/com/google/protobuf/Descriptors.java

@@ -1298,7 +1298,7 @@ public Type getType() {
       // (custom options) into unknown fields.
       if (type == Type.MESSAGE
           && this.features != null
-          && this.features.getMessageEncoding() == FeatureSet.MessageEncoding.DELIMITED) {
+          && getFeatures().getMessageEncoding() == FeatureSet.MessageEncoding.DELIMITED) {
         return Type.GROUP;
       }
       return type;
@@ -1319,13 +1319,13 @@ public boolean needsUtf8Check() {
         // Always enforce strict UTF-8 checking for map fields.
         return true;
       }
-      if (this.features
+      if (getFeatures()
           .getExtension(JavaFeaturesProto.java_)
           .getUtf8Validation()
           .equals(JavaFeatures.Utf8Validation.VERIFY)) {
         return true;
       }
-      return this.features.getUtf8Validation().equals(FeatureSet.Utf8Validation.VERIFY);
+      return getFeatures().getUtf8Validation().equals(FeatureSet.Utf8Validation.VERIFY);
     }
 
     public boolean isMapField() {
@@ -1341,14 +1341,14 @@ && isRepeated()
 
     /** Is this field declared required? */
     public boolean isRequired() {
-      return this.features.getFieldPresence()
+      return getFeatures().getFieldPresence()
           == DescriptorProtos.FeatureSet.FieldPresence.LEGACY_REQUIRED;
     }
 
     /** Is this field declared optional? */
     public boolean isOptional() {
       return proto.getLabel() == FieldDescriptorProto.Label.LABEL_OPTIONAL
-          && this.features.getFieldPresence()
+          && getFeatures().getFieldPresence()
               != DescriptorProtos.FeatureSet.FieldPresence.LEGACY_REQUIRED;
     }
 
@@ -1367,7 +1367,7 @@ public boolean isPacked() {
       if (!isPackable()) {
         return false;
       }
-      return this.features
+      return getFeatures()
           .getRepeatedFieldEncoding()
           .equals(FeatureSet.RepeatedFieldEncoding.PACKED);
     }
@@ -1467,7 +1467,7 @@ public boolean hasPresence() {
           || getType() == Type.GROUP
           || isExtension()
           || getContainingOneof() != null
-          || this.features.getFieldPresence() != DescriptorProtos.FeatureSet.FieldPresence.IMPLICIT;
+          || getFeatures().getFieldPresence() != DescriptorProtos.FeatureSet.FieldPresence.IMPLICIT;
     }
 
     /**
@@ -1476,7 +1476,8 @@ public boolean hasPresence() {
      * been upgraded to editions.
      */
     boolean isGroupLike() {
-      if (features.getMessageEncoding() != DescriptorProtos.FeatureSet.MessageEncoding.DELIMITED) {
+      if (getFeatures().getMessageEncoding()
+          != DescriptorProtos.FeatureSet.MessageEncoding.DELIMITED) {
         // Groups are always tag-delimited.
         return false;
       }
@@ -1577,7 +1578,7 @@ public boolean legacyEnumFieldTreatedAsClosed() {
       }
 
       return getType() == Type.ENUM
-          && (this.features.getExtension(JavaFeaturesProto.java_).getLegacyClosedEnum()
+          && (getFeatures().getExtension(JavaFeaturesProto.java_).getLegacyClosedEnum()
               || enumType.isClosed());
     }
 
@@ -2115,7 +2116,7 @@ public FileDescriptor getFile() {
      * handling quirks.
      */
     public boolean isClosed() {
-      return this.features.getEnumType() == DescriptorProtos.FeatureSet.EnumType.CLOSED;
+      return getFeatures().getEnumType() == DescriptorProtos.FeatureSet.EnumType.CLOSED;
     }
 
     /** If this is a nested type, get the outer descriptor, otherwise null. */
@@ -2811,6 +2812,17 @@ boolean hasInferredLegacyProtoFeatures() {
 
     void validateFeatures() throws DescriptorValidationException {}
 
+    FeatureSet getFeatures() {
+      // TODO: Remove lazy resolution of unresolved features for legacy syntax for
+      // compatibility with older <4.26.x gencode in the next breaking release.
+      if (this.features == null
+          && (getFile().getEdition() == Edition.EDITION_PROTO2
+              || getFile().getEdition() == Edition.EDITION_PROTO3)) {
+        getFile().resolveAllFeaturesImmutable();
+      }
+      return this.features;
+    }
+
     GenericDescriptor parent;
     volatile FeatureSet features;
   }