Partial implementation of #1980

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/JsonNode.java

@@ -1087,7 +1087,7 @@ public final List<JsonNode> findParents(String fieldName)
      */
     public <T extends JsonNode> T withObject(String propertyName) {
         throw new UnsupportedOperationException("JsonNode not of type ObjectNode (but "
-                +getClass().getName()+"), cannot call with() on it");
+                +getClass().getName()+"), cannot call withObject() on it");
     }
 
     /**

src/main/java/com/fasterxml/jackson/databind/node/ArrayNode.java

@@ -68,6 +68,40 @@ public ArrayNode deepCopy()
         return ret;
     }
 
+    @SuppressWarnings("unchecked")
+    @Override
+    protected <T extends JsonNode> T _withObjectCreatePath(JsonPointer origPtr,
+            JsonPointer currentPtr)
+    {
+        // With Arrays, bit different; the first entry needs to be index
+        if (!currentPtr.mayMatchElement()) {
+            return _reportWrongNodeType(
+                    "`JsonPointer` path \"%s\" must have index for `ArrayNode`; instead has property \"%s\"",
+                    origPtr.toString(),
+                    getClass().getName(),
+                    currentPtr.getMatchingProperty());
+        }
+
+        // And we know there's no node at given index
+        ObjectNode currentNode = this.objectNode();
+        // One complication: may need to insert nulls
+        final int ix = currentPtr.getMatchingIndex();
+        while (ix >= size()) {
+            add(nullNode());
+        }
+        set(ix, currentNode);
+
+        currentPtr = currentPtr.tail();
+
+        // Otherwise loop same as with ObjectNode
+        while (!currentPtr.matches()) {
+            // Should we try to build Arrays? For now, nope.
+            currentNode = currentNode.putObject(currentPtr.getMatchingProperty());
+            currentPtr = currentPtr.tail();
+        }
+        return (T) currentNode;
+    }
+
     /*
     /**********************************************************
     /* Overrides for JsonSerializable.Base

src/main/java/com/fasterxml/jackson/databind/node/BaseJsonNode.java

@@ -119,9 +119,39 @@ public <T extends JsonNode> T withObject(JsonPointer ptr) {
         return _withObject(ptr, ptr);
     }
 
+    @SuppressWarnings("unchecked")
     protected <T extends JsonNode> T _withObject(JsonPointer origPtr,
-            JsonPointer currentPTr)  {
-        return null;
+            JsonPointer currentPtr)
+    {
+        if (currentPtr.matches()) {
+            if (this.isObject()) {
+                return (T) this;
+            }
+            return _reportWrongNodeType(
+                    "`JsonNode` matching `JsonPointer` \"%s\" must be `ObjectNode`, not `%s`",
+                    origPtr.toString(),
+                    getClass().getName());
+        }
+        JsonNode n = _at(currentPtr);
+        if ((n != null) && (n instanceof BaseJsonNode)) {
+            return ((BaseJsonNode) n)._withObject(origPtr, currentPtr.tail());
+        }
+        return _withObjectCreatePath(origPtr, currentPtr);
+    }
+
+    /**
+     * Helper method for constructing specified path under this node, if possible;
+     * or throwing an exception if not. If construction successful, needs to return
+     * the innermost {@code ObjectNode} constructed.
+     */
+    protected <T extends JsonNode> T _withObjectCreatePath(JsonPointer origPtr,
+            JsonPointer currentPtr)
+    {
+        // Cannot traverse non-container nodes:
+        return _reportWrongNodeType(
+                "`JsonPointer` path \"%s\" cannot traverse non-container node of type `%s`",
+                origPtr.toString(),
+                getClass().getName());
     }
 
     /*

src/main/java/com/fasterxml/jackson/databind/node/ObjectNode.java

@@ -60,6 +60,20 @@ public ObjectNode deepCopy()
         return ret;
     }
 
+    @SuppressWarnings("unchecked")
+    @Override
+    protected <T extends JsonNode> T _withObjectCreatePath(JsonPointer origPtr,
+            JsonPointer currentPtr)
+    {
+        ObjectNode currentNode = this;
+        while (!currentPtr.matches()) {
+            // Should we try to build Arrays? For now, nope.
+            currentNode = currentNode.putObject(currentPtr.getMatchingProperty());
+            currentPtr = currentPtr.tail();
+        }
+        return (T) currentNode;
+    }
+
     /*
     /**********************************************************
     /* Overrides for JsonSerializable.Base

src/test/java/com/fasterxml/jackson/databind/node/WithPathTest.java

@@ -0,0 +1,60 @@
+package com.fasterxml.jackson.databind.node;
+
+import com.fasterxml.jackson.core.JsonPointer;
+import com.fasterxml.jackson.databind.*;
+
+// for [databuind#1980] implementation
+public class WithPathTest extends BaseMapTest
+{
+    /*
+    /**********************************************************************
+    /* Test methods
+    /**********************************************************************
+     */
+
+    private final ObjectMapper MAPPER = sharedMapper();
+
+    public void testValidWithObjectTrivial() throws Exception
+    {
+        ObjectNode root = MAPPER.createObjectNode();
+        ObjectNode match = root.withObject(JsonPointer.empty());
+        assertSame(root, match);
+    }
+
+    public void testValidWithObjectSimple() throws Exception
+    {
+        ObjectNode root = MAPPER.createObjectNode();
+        ObjectNode match = root.withObject(JsonPointer.compile("/a/b"));
+        assertTrue(match.isObject());
+        match.put("value", 42);
+
+        assertEquals(a2q("{'a':{'b':{'value':42}}}"),
+                root.toString());
+
+        // and with that
+        ObjectNode match2 = root.withObject(JsonPointer.compile("/a/b"));
+        assertSame(match, match2);
+        match.put("value2", true);
+
+        assertEquals(a2q("{'a':{'b':{'value':42,'value2':true}}}"),
+                root.toString());
+    }
+
+    public void testValidWithObjectWithArray() throws Exception
+    {
+        ObjectNode root = MAPPER.createObjectNode();
+        root.putArray("arr");
+        ObjectNode match = root.withObject(JsonPointer.compile("/arr/2"));
+        assertTrue(match.isObject());
+        match.put("value", 42);
+        assertEquals(a2q("{'arr':[null,null,{'value':42}]}"),
+                root.toString());
+
+        // But also verify we can match
+        ObjectNode match2 = root.withObject(JsonPointer.compile("/arr/2"));
+        assertSame(match, match2);
+        match.put("value2", true);
+        assertEquals(a2q("{'arr':[null,null,{'value':42,'value2':true}]}"),
+                root.toString());
+    }
+}