Fix toJson for cyclic values

ballerina/json_api.bal

@@ -55,18 +55,8 @@ public isolated function parseStream(stream<byte[], error?> s, Options options =
 #
 # + v - Source anydata value
 # + return - representation of `v` as value of type json
-public isolated function toJson(anydata v) returns json {
-    if v is anydata[] {
-        return from anydata elem in v
-            select toJson(elem);
-    } else if v is map<anydata> {
-        return map from var [key, feild] in v.entries()
-            select [getNameAnnotation(v, key), toJson(feild)];
-    }
-    return v.toJson();
-}
-
-isolated function getNameAnnotation(map<anydata> data, string key) returns string = @java:Method {'class: "io.ballerina.lib.data.jsondata.json.Native"} external;
+public isolated function toJson(anydata v) returns json =
+    @java:Method {'class: "io.ballerina.lib.data.jsondata.json.Native"} external;
 
 # Prettifies a `json` value to print it.
 #

ballerina/tests/to_json_test.bal

@@ -173,3 +173,49 @@ function testToJsonWithNameANnotation() {
     test:assertTrue(j2 is json);
     test:assertEquals(j2, out2);
 }
+
+type TestRecord4 record {|
+    @Name {
+        value: "a-o"
+    }
+    string a;
+    @Name {
+        value: "b-o"
+    }
+    string b;
+    int c;
+    TestRecord4[] d;
+|};
+
+@test:Config
+function testToJsonWithCyclicValues() {
+    json[] v1 = [];
+    v1.push(v1);
+    json|error r1 = trap toJsonWithCyclicValues(v1);
+    test:assertTrue(r1 is error);
+    error r1Err = <error> r1;
+    test:assertEquals("the value has a cyclic reference", r1Err.message());
+
+    map<json> v2 = {};
+    v2["val"] = v2;
+    json|error r2 = trap toJsonWithCyclicValues(v2);
+    test:assertTrue(r2 is error);
+    error r2Err = <error> r2;
+    test:assertEquals("the value has a cyclic reference", r2Err.message());
+
+    TestRecord4 v3 = {
+        a: "a-v",
+        b: "b-v",
+        c: 1,
+        d: []
+    };
+    v3.d.push(v3);
+    json|error r3 = trap toJsonWithCyclicValues(v3);
+    test:assertTrue(r3 is error);
+    error r3Err = <error> r3;
+    test:assertEquals("the value has a cyclic reference", r3Err.message());
+}
+
+function toJsonWithCyclicValues(anydata val) returns json {
+    return toJson(val);
+}

native/src/main/java/io/ballerina/lib/data/jsondata/json/Native.java

@@ -21,9 +21,15 @@
 import io.ballerina.lib.data.jsondata.io.DataReaderTask;
 import io.ballerina.lib.data.jsondata.io.DataReaderThreadPool;
 import io.ballerina.lib.data.jsondata.utils.Constants;
+import io.ballerina.lib.data.jsondata.utils.DiagnosticErrorCode;
+import io.ballerina.lib.data.jsondata.utils.DiagnosticLog;
 import io.ballerina.runtime.api.Environment;
 import io.ballerina.runtime.api.Future;
+import io.ballerina.runtime.api.PredefinedTypes;
+import io.ballerina.runtime.api.creators.TypeCreator;
+import io.ballerina.runtime.api.creators.ValueCreator;
 import io.ballerina.runtime.api.types.RecordType;
+import io.ballerina.runtime.api.utils.JsonUtils;
 import io.ballerina.runtime.api.utils.StringUtils;
 import io.ballerina.runtime.api.values.BArray;
 import io.ballerina.runtime.api.values.BError;
@@ -36,7 +42,9 @@
 import java.io.ByteArrayInputStream;
 import java.io.InputStreamReader;
 import java.io.StringReader;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Set;
 
 import static io.ballerina.lib.data.jsondata.json.JsonCreator.getModifiedName;
 import static io.ballerina.lib.data.jsondata.utils.DataUtils.unescapeIdentifier;
@@ -82,6 +90,40 @@ public static Object parseStream(Environment env, BStream json, BMap<BString, Ob
         return null;
     }
 
+    public static Object toJson(Object value) {
+        return toJson(value, new HashSet<>());
+    }
+
+    public static Object toJson(Object value, Set<Object> visitedValues) {
+        if (!visitedValues.add(value)) {
+            throw DiagnosticLog.error(DiagnosticErrorCode.CYCLIC_REFERENCE);
+        }
+
+        if (value instanceof BArray listValue) {
+            int length = (int) listValue.getLength();
+            Object[] convertedValues = new Object[length];
+            for (int i = 0; i < length; i++) {
+                convertedValues[i] = toJson(listValue.get(i), visitedValues);
+            }
+            return ValueCreator.createArrayValue(convertedValues, PredefinedTypes.TYPE_JSON_ARRAY);
+        }
+
+        if (value instanceof BMap) {
+            BMap<BString, Object> mapValue = (BMap<BString, Object>) value;
+            BMap<BString, Object> jsonObject =
+                    ValueCreator.createMapValue(TypeCreator.createMapType(PredefinedTypes.TYPE_JSON));
+
+            for (BString entryKey : mapValue.getKeys()) {
+                Object entryValue = mapValue.get(entryKey);
+                jsonObject.put(getNameAnnotation(mapValue, entryKey), toJson(entryValue, visitedValues));
+            }
+
+            return jsonObject;
+        }
+
+        return JsonUtils.convertToJson(value);
+    }
+
     public static BString getNameAnnotation(BMap<BString, Object> value, BString key) {
         if (!(value.getType() instanceof RecordType recordType)) {
             return key;

native/src/main/java/io/ballerina/lib/data/jsondata/utils/DiagnosticErrorCode.java

@@ -36,7 +36,8 @@ public enum DiagnosticErrorCode {
     INVALID_TYPE_FOR_FIELD("JSON_ERROR_009", "invalid.type.for.field"),
     DUPLICATE_FIELD("JSON_ERROR_010", "duplicate.field"),
     CANNOT_CONVERT_TO_EXPECTED_TYPE("JSON_ERROR_011", "cannot.convert.to.expected.type"),
-    UNDEFINED_FIELD("JSON_ERROR_012", "undefined.field");
+    UNDEFINED_FIELD("JSON_ERROR_012", "undefined.field"),
+    CYCLIC_REFERENCE("JSON_ERROR_013", "cyclic.reference");
 
     String diagnosticId;
     String messageKey;

native/src/main/resources/json_error.properties

@@ -55,3 +55,6 @@ error.cannot.convert.to.expected.type=\
 
 error.undefined.field=\
   undefined field ''{0}''
+
+error.cyclic.reference=\
+  the value has a cyclic reference