Add test for #4934, minor fix (#4940)

Author: cowtowncoder

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

@@ -1074,7 +1074,7 @@ public JsonNode readTree(JsonParser p) throws IOException {
      */
     public <T> T readTreeAsValue(JsonNode n, Class<T> targetType) throws IOException
     {
-        if (n == null) {
+        if (n == null || n.isMissingNode()) {
             return null;
         }
         try (TreeTraversingParser p = _treeAsTokens(n)) {
@@ -1098,7 +1098,7 @@ public <T> T readTreeAsValue(JsonNode n, Class<T> targetType) throws IOException
      */
     public <T> T readTreeAsValue(JsonNode n, JavaType targetType) throws IOException
     {
-        if (n == null) {
+        if (n == null || n.isMissingNode()) {
             return null;
         }
         try (TreeTraversingParser p = _treeAsTokens(n)) {

src/test/java/com/fasterxml/jackson/databind/DeserializationContextTest.java

@@ -0,0 +1,53 @@
+package com.fasterxml.jackson.databind;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.node.JsonNodeFactory;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+public class DeserializationContextTest extends DatabindTestUtil
+{
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    static class Bean4934 {
+        public String value;
+    }
+
+    // [databind#4934]
+    @Test
+    public void testTreeAsValueFromNulls() throws Exception
+    {
+        final JsonNodeFactory nodeF = MAPPER.getNodeFactory();
+        try (JsonParser p = MAPPER.createParser("abc")) {
+            DeserializationContext ctxt = MAPPER.readerFor(String.class).createDeserializationContext(p);
+
+            assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), Boolean.class));
+            assertEquals(Boolean.FALSE, ctxt.readTreeAsValue(nodeF.nullNode(), Boolean.TYPE));
+
+            // Only fixed in 2.19:
+            //assertNull(ctxt.readTreeAsValue(nodeF.nullNode(), Bean4934.class));
+
+        }
+    }
+
+    // [databind#4934]
+    @Test
+    public void testTreeAsValueFromMissing() throws Exception
+    {
+        final JsonNodeFactory nodeF = MAPPER.getNodeFactory();
+        try (JsonParser p = MAPPER.createParser("abc")) {
+            DeserializationContext ctxt = MAPPER.readerFor(String.class).createDeserializationContext(p);
+
+            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Boolean.class));
+            // Absent becomes `null` for now as well
+            assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Boolean.TYPE));
+
+            // Only fixed in 2.19:
+            //assertNull(ctxt.readTreeAsValue(nodeF.missingNode(), Bean4934.class));
+        }
+    }
+}