#71: Support proto3 extensions

While proto3 replaces regular extensions with Any, custom options are
a valid use for the extension mechanism.

Author: kshchepanovskyi

src/main/java/io/protostuff/jetbrains/plugin/annotator/ProtoErrorsAnnotator.java

@@ -3,6 +3,7 @@
 import static io.protostuff.jetbrains.plugin.ProtostuffBundle.message;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableSet;
 import com.intellij.codeInspection.ProblemHighlightType;
 import com.intellij.lang.ASTNode;
 import com.intellij.lang.annotation.Annotation;
@@ -11,6 +12,7 @@
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiReference;
 import io.protostuff.compiler.model.Field;
+import io.protostuff.compiler.model.ProtobufConstants;
 import io.protostuff.jetbrains.plugin.psi.AntlrParserRuleNode;
 import io.protostuff.jetbrains.plugin.psi.EnumConstantNode;
 import io.protostuff.jetbrains.plugin.psi.EnumNode;
@@ -54,6 +56,16 @@ public class ProtoErrorsAnnotator implements Annotator {
     private static final int SYS_RESERVED_START = 19000;
     private static final int SYS_RESERVED_END = 19999;
 
+    private static final Set<String> VALID_PROTO3_EXTENDEES = ImmutableSet.of(
+            ProtobufConstants.MSG_ENUM_OPTIONS,
+            ProtobufConstants.MSG_ENUM_VALUE_OPTIONS,
+            ProtobufConstants.MSG_FIELD_OPTIONS,
+            ProtobufConstants.MSG_FILE_OPTIONS,
+            ProtobufConstants.MSG_MESSAGE_OPTIONS,
+            ProtobufConstants.MSG_METHOD_OPTIONS,
+            ProtobufConstants.MSG_ONEOF_OPTIONS,
+            ProtobufConstants.MSG_SERVICE_OPTIONS
+    );
     private AnnotationHolder holder;
 
     @Override
@@ -145,11 +157,27 @@ private void checkFirstEnumConstantValueIsZero(EnumNode anEnum, List<EnumConstan
     }
 
     private void checkExtendNodeDeprecated(ExtendNode element, Syntax syntax) {
-        if (syntax != Syntax.PROTO3) {
+        PsiElement extendee = null;
+        TypeReferenceNode target = element.getTarget();
+        if (target != null) {
+            PsiReference reference = target.getReference();
+            if (reference != null) {
+                extendee = reference.resolve();
+            }
+        }
+        if (!(extendee instanceof MessageNode)) {
+            String message = message("error.extensions.not.supported");
+            markError(element.getNode(), element.getTargetNode(), message);
             return;
         }
-        String message = message("error.extensions.not.supported");
-        markError(element.getNode(), null, message);
+        if (syntax == Syntax.PROTO3) {
+            MessageNode message = (MessageNode) extendee;
+            String qualifiedName = message.getQualifiedName();
+            if (!VALID_PROTO3_EXTENDEES.contains(qualifiedName)) {
+                String text = message("error.extensions.not.supported");
+                markError(element.getNode(), element.getTargetNode(), text);
+            }
+        }
     }
 
     private void checkGroupNodeDeprecated(GroupNode element, Syntax syntax) {

src/main/java/io/protostuff/jetbrains/plugin/psi/ExtendNode.java

@@ -22,6 +22,17 @@ public TypeReferenceNode getTarget() {
         return findChildByClass(TypeReferenceNode.class);
     }
 
+    /**
+     * Returns extendee name node, if it exists.
+     */
+    public ASTNode getTargetNode() {
+        TypeReferenceNode target = getTarget();
+        if (target != null) {
+            return target.getNode();
+        }
+        return null;
+    }
+
     /**
      * Returns namespace for fields of this extension.
      */

src/main/resources/io/protostuff/protobuf-jetbrains-plugin/messages/ProtostuffBundle.properties

@@ -25,7 +25,7 @@ error.missing.field.label=Missing field label
 error.illegal.field.label=Field label "{0}" is not allowed in proto3
 error.default.value.not.supported=Default values are not supported in proto3
 error.groups.not.supported=Groups are not supported in proto3
-error.extensions.not.supported=Extensions are not supported in proto3
+error.extensions.not.supported=Cannot extend given type
 error.first.enum.value.should.be.zero=First enum value must be zero in proto3
 error.illegal.oneof.field.label=Oneof field cannot have label
 error.unresolved.reference=Unresolved reference

src/test/java/io/protostuff/jetbrains/plugin/annotator/ProtoErrorsAnnotatorTest.java

@@ -94,6 +94,14 @@ public void testProto3IllegalGroup() {
         check();
     }
 
+    public void testProto3ValidExtend() {
+        check();
+    }
+
+    public void testProto2IllegalExtend() {
+        check();
+    }
+
     public void testProto3IllegalExtend() {
         check();
     }

src/test/resources/annotator/Proto2IllegalExtend.proto

@@ -0,0 +1,11 @@
+syntax = "proto2";
+
+package annotator;
+
+enum RegularEnum {
+
+}
+
+extend <error descr="Cannot extend given type">RegularEnum</error> {
+
+}

src/test/resources/annotator/Proto3IllegalExtend.proto

@@ -2,8 +2,10 @@ syntax = "proto3";
 
 package annotator;
 
-import "google/protobuf/descriptor.proto";
+message RegularMessage {
 
-<error descr="Extensions are not supported in proto3">extend google.protobuf.MessageOptions {
+}
 
-}</error>
+extend <error descr="Cannot extend given type">RegularMessage</error> {
+
+}

src/test/resources/annotator/Proto3ValidExtend.proto

@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package annotator;
+
+import "google/protobuf/descriptor.proto";
+
+extend google.protobuf.MessageOptions {
+
+}