Add option to enable strict JSON parsing in Protobuf Java JsonFormat.

JsonFormat used 'reader.setLenient(false)' to try to get spec JSON behavior out of GSON. However, this mode was still not actually spec JSON. In ~2024 GSON deprecated setLenient(), made that behavior LEGACY_STRICT and added a new level STRICT which is intended to be spec.

Switching unilaterally would be a breaking change for Protobuf: this change just adds the option for users to ask us to use GSON in strict mode. At a later date we will consider flipping the default of this (letting people opt into LEGACY_STRICT if they want to).

PiperOrigin-RevId: 921432331

Author: protobuf-github-bot

java/util/src/main/java/com/google/protobuf/util/JsonFormat.java

@@ -489,7 +489,8 @@ public static Parser parser() {
         TypeRegistry.getEmptyTypeRegistry(),
         ExtensionRegistry.getEmptyRegistry(),
         false,
-        Parser.DEFAULT_RECURSION_LIMIT);
+        Parser.DEFAULT_RECURSION_LIMIT,
+        true);
   }
 
   /** A Parser parses the ProtoJSON format into a protobuf message. */
@@ -499,6 +500,7 @@ public static class Parser {
     private final ExtensionRegistry extensionRegistry;
     private final boolean ignoringUnknownFields;
     private final int recursionLimit;
+    private final boolean legacyLenient;
 
     // The default parsing recursion limit is aligned with the proto binary parser.
     private static final int DEFAULT_RECURSION_LIMIT = 100;
@@ -508,12 +510,14 @@ private Parser(
         TypeRegistry oldRegistry,
         ExtensionRegistry extensionRegistry,
         boolean ignoreUnknownFields,
-        int recursionLimit) {
+        int recursionLimit,
+        boolean legacyLenient) {
       this.registry = registry;
       this.oldRegistry = oldRegistry;
       this.extensionRegistry = extensionRegistry;
       this.ignoringUnknownFields = ignoreUnknownFields;
       this.recursionLimit = recursionLimit;
+      this.legacyLenient = legacyLenient;
     }
 
     /**
@@ -532,7 +536,8 @@ public Parser usingTypeRegistry(TypeRegistry oldRegistry) {
           oldRegistry,
           extensionRegistry,
           ignoringUnknownFields,
-          recursionLimit);
+          recursionLimit,
+          legacyLenient);
     }
 
     /**
@@ -547,7 +552,12 @@ public Parser usingTypeRegistry(com.google.protobuf.TypeRegistry registry) {
         throw new IllegalArgumentException("Only one registry is allowed.");
       }
       return new Parser(
-          registry, oldRegistry, extensionRegistry, ignoringUnknownFields, recursionLimit);
+          registry,
+          oldRegistry,
+          extensionRegistry,
+          ignoringUnknownFields,
+          recursionLimit,
+          legacyLenient);
     }
 
     /**
@@ -559,15 +569,21 @@ Parser usingExtensionRegistry(ExtensionRegistry extensionRegistry) {
         throw new NullPointerException();
       }
       return new Parser(
-          registry, oldRegistry, extensionRegistry, ignoringUnknownFields, recursionLimit);
+          registry,
+          oldRegistry,
+          extensionRegistry,
+          ignoringUnknownFields,
+          recursionLimit,
+          legacyLenient);
     }
 
     /**
      * Creates a new {@link Parser} configured to not throw an exception when an unknown field is
      * encountered. The new Parser clones all other configurations from this Parser.
      */
     public Parser ignoringUnknownFields() {
-      return new Parser(this.registry, oldRegistry, extensionRegistry, true, recursionLimit);
+      return new Parser(
+          this.registry, oldRegistry, extensionRegistry, true, recursionLimit, legacyLenient);
     }
 
     /**
@@ -580,7 +596,12 @@ public void merge(String json, Message.Builder builder) throws InvalidProtocolBu
       // TODO: Investigate the allocation overhead and optimize for
       // mobile.
       new ParserImpl(
-              registry, oldRegistry, extensionRegistry, ignoringUnknownFields, recursionLimit)
+              registry,
+              oldRegistry,
+              extensionRegistry,
+              ignoringUnknownFields,
+              recursionLimit,
+              legacyLenient)
           .merge(json, builder);
     }
 
@@ -595,14 +616,24 @@ public void merge(Reader json, Message.Builder builder) throws IOException {
       // TODO: Investigate the allocation overhead and optimize for
       // mobile.
       new ParserImpl(
-              registry, oldRegistry, extensionRegistry, ignoringUnknownFields, recursionLimit)
+              registry,
+              oldRegistry,
+              extensionRegistry,
+              ignoringUnknownFields,
+              recursionLimit,
+              legacyLenient)
           .merge(json, builder);
     }
 
     // For testing only.
     Parser usingRecursionLimit(int recursionLimit) {
       return new Parser(
-          registry, oldRegistry, extensionRegistry, ignoringUnknownFields, recursionLimit);
+          registry,
+          oldRegistry,
+          extensionRegistry,
+          ignoringUnknownFields,
+          recursionLimit,
+          legacyLenient);
     }
   }
 
@@ -1411,25 +1442,31 @@ private static class ParserImpl {
     private final ExtensionRegistry extensionRegistry;
     private final boolean ignoringUnknownFields;
     private final int recursionLimit;
+    private final boolean legacyLenient;
     private int currentDepth;
 
     ParserImpl(
         com.google.protobuf.TypeRegistry registry,
         TypeRegistry oldRegistry,
         ExtensionRegistry extensionRegistry,
         boolean ignoreUnknownFields,
-        int recursionLimit) {
+        int recursionLimit,
+        boolean legacyLenient) {
       this.registry = registry;
       this.oldRegistry = oldRegistry;
       this.extensionRegistry = extensionRegistry;
       this.ignoringUnknownFields = ignoreUnknownFields;
       this.recursionLimit = recursionLimit;
+      this.legacyLenient = legacyLenient;
       this.currentDepth = 0;
     }
 
     void merge(Reader json, Message.Builder builder) throws IOException {
       try {
         JsonReader reader = new JsonReader(json);
+        if (!legacyLenient) {
+          throw new IllegalStateException("Unreachable: !legacyLenient should not be set.");
+        }
         reader.setLenient(false);
         merge(JsonParser.parseReader(reader), builder);
       } catch (JsonIOException e) {
@@ -1448,6 +1485,9 @@ void merge(Reader json, Message.Builder builder) throws IOException {
     void merge(String json, Message.Builder builder) throws InvalidProtocolBufferException {
       try {
         JsonReader reader = new JsonReader(new StringReader(json));
+        if (!legacyLenient) {
+          throw new IllegalStateException("Strict parsing is not supported in open-source.");
+        }
         reader.setLenient(false);
         merge(JsonParser.parseReader(reader), builder);
       } catch (RuntimeException e) {