Fix #5179: add "currentToken" in MismatchedInputException (and sub-types) (#5180)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -18,6 +18,7 @@ Project: jackson-databind
   serialization
 #5151: Add new exception type, `MissingInjectValueException`, to be used
   for failed `@JacksonInject`
+#5179: Add "current token" info into `MismatchedInputException`
 - Generate SBOMs [JSTEP-14]
 
 2.19.1 (not yet released)

src/main/java/com/fasterxml/jackson/databind/exc/MismatchedInputException.java

@@ -1,7 +1,6 @@
 package com.fasterxml.jackson.databind.exc;
 
-import com.fasterxml.jackson.core.JsonLocation;
-import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.util.ClassUtil;
@@ -31,22 +30,36 @@ public class MismatchedInputException
      */
     protected Class<?> _targetType;
 
+    /**
+     * Current token at the point when exception was thrown (if available).
+     *
+     * @since 2.20
+     */
+    protected JsonToken _currentToken;
+
     protected MismatchedInputException(JsonParser p, String msg) {
         this(p, msg, (JavaType) null);
     }
 
     protected MismatchedInputException(JsonParser p, String msg, JsonLocation loc) {
         super(p, msg, loc);
+        _currentToken = _currentToken(p);
     }
 
     protected MismatchedInputException(JsonParser p, String msg, Class<?> targetType) {
         super(p, msg);
         _targetType = targetType;
+        _currentToken = _currentToken(p);
     }
 
     protected MismatchedInputException(JsonParser p, String msg, JavaType targetType) {
         super(p, msg);
         _targetType = ClassUtil.rawClass(targetType);
+        _currentToken = _currentToken(p);
+    }
+
+    protected static JsonToken _currentToken(JsonParser p) {
+         return (p == null) ? null : p.currentToken();
     }
 
     // Only to prevent super-class static method from getting called
@@ -68,11 +81,25 @@ public MismatchedInputException setTargetType(JavaType t) {
         return this;
     }
 
+    public MismatchedInputException setCurrentToken(JsonToken t) {
+        _currentToken = t;
+        return this;
+    }
+
     /**
      * Accessor for getting intended target type, with which input did not match,
      * if known; `null` if not known for some reason.
      */
     public Class<?> getTargetType() {
         return _targetType;
     }
+
+    /**
+     * @return Current token at the point when exception was thrown, if available
+     *   ({@code null} if not)
+     * @since 2.20
+     */
+    public JsonToken getCurrentToken() {
+        return _currentToken;
+    }
 }

src/test/java/com/fasterxml/jackson/databind/convert/CoerceToBooleanTest.java

@@ -413,11 +413,10 @@ private void _verifyBooleanCoerceFailReason(MismatchedInputException e,
             JsonToken tokenType, String tokenValue) throws IOException
     {
         verifyException(e, "Cannot coerce ", "Cannot deserialize value of type ");
+        // 30-May-2025, tatu: [databind#5179] got access via exception now
+        assertToken(tokenType, e.getCurrentToken());
 
         JsonParser p = (JsonParser) e.getProcessor();
-
-        assertToken(tokenType, p.currentToken());
-
         final String text = p.getText();
         if (!tokenValue.equals(text)) {
             String textDesc = (text == null) ? "NULL" : q(text);

src/test/java/com/fasterxml/jackson/databind/exc/DeserExceptionTypeTest.java

@@ -7,20 +7,20 @@
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.testutil.BrokenStringReader;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.fail;
 
-import static com.fasterxml.jackson.databind.testutil.DatabindTestUtil.newJsonMapper;
-import static com.fasterxml.jackson.databind.testutil.DatabindTestUtil.verifyException;
-
 /**
  * Unit test for verifying that exceptions are properly handled (caught,
  * re-thrown or wrapped, depending) with Object deserialization,
  * including using concrete subtypes of {@link DatabindException}
  * (and streaming-level equivalents).
  */
 public class DeserExceptionTypeTest
+    extends DatabindTestUtil
 {
     static class Bean {
         public String propX;
@@ -59,6 +59,8 @@ public void testHandlingOfUnrecognized() throws Exception
         assertEquals(Bean.class, exc.getReferringClass());
         // also: should get list of known properties
         verifyException(exc, "propX");
+        // and as per [databind#5179] current token (pointing to start of value?)
+        assertEquals(JsonToken.VALUE_NUMBER_INT, exc.getCurrentToken());
     }
 
     /**
@@ -73,6 +75,7 @@ public void testExceptionWithEmpty() throws Exception
             fail("Expected an exception, but got result value: "+result);
         } catch (MismatchedInputException e) {
             verifyException(e, "No content");
+            assertNull(e.getCurrentToken());
         }
     }
 
@@ -106,6 +109,7 @@ public void testExceptionWithEOF() throws Exception
             fail("Should have gotten an exception");
         } catch (MismatchedInputException e) {
             verifyException(e, "No content");
+            assertNull(e.getCurrentToken());
         }
         // also: should have no current token after end-of-input
         JsonToken t = p.currentToken();