Start implementing "content nulls" handling for some of collections

src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializerBase.java

@@ -6,7 +6,7 @@
 import java.util.*;
 
 import com.fasterxml.jackson.annotation.*;
-import com.fasterxml.jackson.annotation.JsonSetter.Nulls;
+
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.core.JsonParser.NumberType;
 
@@ -920,46 +920,13 @@ protected SettableBeanProperty _resolveMergeAndNullSettings(DeserializationConte
         }
 
         // And after this, see if we require non-standard null handling
-        NullValueProvider nuller = _findNullProvider(ctxt, prop, propMetadata);
+        NullValueProvider nuller = findValueNullProvider(ctxt, prop, propMetadata);
         if (nuller != null) {
             prop = prop.withNullProvider(nuller);
         }
         return prop;
     }
 
-    // @since 2.9
-    protected NullValueProvider _findNullProvider(DeserializationContext ctxt,
-            SettableBeanProperty prop, PropertyMetadata propMetadata)
-        throws JsonMappingException
-    {
-        final Nulls nulls = propMetadata.getValueNulls();
-        if (nulls != null) {
-            switch (nulls) {
-            case FAIL:
-                return new NullsFailProvider(prop.getFullName(), prop.getType());
-            case AS_EMPTY:
-                // Let's first do some sanity checking...
-                {
-                    JsonDeserializer<?> deser = prop.getValueDeserializer();
-                    // NOTE: although we could use `ValueInstantiator.Gettable` in general,
-                    // let's not since that would prevent being able to use custom impls:
-                    if (deser instanceof BeanDeserializerBase) {
-                        ValueInstantiator vi = ((BeanDeserializerBase) deser).getValueInstantiator();
-                        if (!vi.canCreateUsingDefault()) {
-                            final JavaType type = prop.getType();
-                            ctxt.reportBadDefinition(type,
-                                    String.format("Can not create empty instance of %s, no default Creator", type));
-                        }
-                    }
-                    return new NullsAsEmptyProvider(deser);
-                }
-            case SKIP: // can't do here
-            default: // SET/DEFAULT, nothing to do; S
-            }
-        }
-        return null;
-    }
-
     /*
     /**********************************************************
     /* Public accessors

src/main/java/com/fasterxml/jackson/databind/deser/NullValueProvider.java

@@ -14,6 +14,12 @@
  */
 public interface NullValueProvider
 {
+    /**
+     * Marker object used in some context to mark return value that is to indicate
+     * that `null` should be skipped (instead of being replaced).
+     */
+    public final static Object SKIP_MARKER = new Object();
+
     /**
      * Method called to possibly convert incoming `null` token (read via
      * underlying streaming input source) into other value of type accessor

src/main/java/com/fasterxml/jackson/databind/deser/impl/NullsConstantProvider.java

@@ -0,0 +1,34 @@
+package com.fasterxml.jackson.databind.deser.impl;
+
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.deser.NullValueProvider;
+import com.fasterxml.jackson.databind.exc.InvalidNullException;
+
+/**
+ * Simple {@link NullValueProvider} that will always throw a
+ * {@link InvalidNullException} when a null is encountered.
+ */
+public class NullsConstantProvider implements NullValueProvider
+{
+    private final static NullsConstantProvider SKIPPER = new NullsConstantProvider(NullValueProvider.SKIP_MARKER);
+
+    protected final Object _nullValue;
+
+    public NullsConstantProvider(Object nvl) {
+        _nullValue = nvl;
+    }
+
+    /**
+     * Static accessor for a stateless instance that always returns
+     * {@link NullValueProvider#SKIP_MARKER} marker instance, used to indicate
+     * that null value is to be skipped instead of replacing it.
+     */
+    public static NullsConstantProvider skipper() {
+        return SKIPPER;
+    }
+
+    @Override
+    public Object getNullValue(DeserializationContext ctxt) {
+        return _nullValue;
+    }
+}

src/main/java/com/fasterxml/jackson/databind/deser/std/ArrayBlockingQueueDeserializer.java

@@ -6,6 +6,7 @@
 
 import com.fasterxml.jackson.core.JsonParser;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.deser.NullValueProvider;
 import com.fasterxml.jackson.databind.deser.ValueInstantiator;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
 
@@ -38,10 +39,11 @@ public ArrayBlockingQueueDeserializer(JavaType containerType,
      protected ArrayBlockingQueueDeserializer(JavaType containerType,
             JsonDeserializer<Object> valueDeser, TypeDeserializer valueTypeDeser,
             ValueInstantiator valueInstantiator,
-            JsonDeserializer<Object> delegateDeser, Boolean unwrapSingle)
+            JsonDeserializer<Object> delegateDeser,
+            NullValueProvider nuller, Boolean unwrapSingle)
     {
-        super(containerType, valueDeser, valueTypeDeser, valueInstantiator,
-                delegateDeser, unwrapSingle);
+        super(containerType, valueDeser, valueTypeDeser, valueInstantiator, delegateDeser,
+                nuller, unwrapSingle);
     }
 
     /**
@@ -58,11 +60,13 @@ protected ArrayBlockingQueueDeserializer(ArrayBlockingQueueDeserializer src) {
     @Override
     @SuppressWarnings("unchecked")
     protected ArrayBlockingQueueDeserializer withResolved(JsonDeserializer<?> dd,
-            JsonDeserializer<?> vd, TypeDeserializer vtd, Boolean unwrapSingle)
+            JsonDeserializer<?> vd, TypeDeserializer vtd,
+            NullValueProvider nuller, Boolean unwrapSingle)
     {
         return new ArrayBlockingQueueDeserializer(_containerType,
                 (JsonDeserializer<Object>) vd, vtd,
-                _valueInstantiator, (JsonDeserializer<Object>) dd, unwrapSingle);
+                _valueInstantiator, (JsonDeserializer<Object>) dd,
+                nuller, unwrapSingle);
     }
 
     /*

src/main/java/com/fasterxml/jackson/databind/deser/std/CollectionDeserializer.java

@@ -4,12 +4,12 @@
 import java.util.*;
 
 import com.fasterxml.jackson.annotation.JsonFormat;
+
 import com.fasterxml.jackson.core.*;
+
 import com.fasterxml.jackson.databind.*;
 import com.fasterxml.jackson.databind.annotation.JacksonStdImpl;
-import com.fasterxml.jackson.databind.deser.ContextualDeserializer;
-import com.fasterxml.jackson.databind.deser.UnresolvedForwardReference;
-import com.fasterxml.jackson.databind.deser.ValueInstantiator;
+import com.fasterxml.jackson.databind.deser.*;
 import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId.Referring;
 import com.fasterxml.jackson.databind.deser.std.ContainerDeserializerBase;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
@@ -54,6 +54,13 @@ public class CollectionDeserializer
      */
     protected final JsonDeserializer<Object> _delegateDeserializer;
 
+    /**
+     * Handler we need for dealing with nulls
+     *
+     * @since 2.9
+     */
+    protected final NullValueProvider _nullProvider;
+
     /**
      * Specific override for this instance (from proper, or global per-type overrides)
      * to indicate whether single value may be taken to mean an unwrapped one-element array
@@ -79,24 +86,26 @@ public CollectionDeserializer(JavaType collectionType,
             JsonDeserializer<Object> valueDeser,
             TypeDeserializer valueTypeDeser, ValueInstantiator valueInstantiator)
     {
-        this(collectionType, valueDeser, valueTypeDeser, valueInstantiator, null, null);
+        this(collectionType, valueDeser, valueTypeDeser, valueInstantiator, null, null, null);
     }
 
     /**
      * Constructor used when creating contextualized instances.
+     *
+     * @since 2.9
      */
     protected CollectionDeserializer(JavaType collectionType,
             JsonDeserializer<Object> valueDeser, TypeDeserializer valueTypeDeser,
-            ValueInstantiator valueInstantiator,
-            JsonDeserializer<Object> delegateDeser,
-            Boolean unwrapSingle)
+            ValueInstantiator valueInstantiator, JsonDeserializer<Object> delegateDeser,
+            NullValueProvider nuller, Boolean unwrapSingle)
     {
         super(collectionType);
         _valueDeserializer = valueDeser;
         _valueTypeDeserializer = valueTypeDeser;
         _valueInstantiator = valueInstantiator;
         _delegateDeserializer = delegateDeser;
         _unwrapSingle = unwrapSingle;
+        _nullProvider = nuller;
     }
 
     /**
@@ -111,21 +120,23 @@ protected CollectionDeserializer(CollectionDeserializer src)
         _valueInstantiator = src._valueInstantiator;
         _delegateDeserializer = src._delegateDeserializer;
         _unwrapSingle = src._unwrapSingle;
+        _nullProvider = src._nullProvider;
     }
 
     /**
      * Fluent-factory method call to construct contextual instance.
      *
-     * @since 2.7
+     * @since 2.9
      */
     @SuppressWarnings("unchecked")
     protected CollectionDeserializer withResolved(JsonDeserializer<?> dd,
             JsonDeserializer<?> vd, TypeDeserializer vtd,
-            Boolean unwrapSingle)
+            NullValueProvider nuller, Boolean unwrapSingle)
     {
         return new CollectionDeserializer(_containerType,
                 (JsonDeserializer<Object>) vd, vtd,
-                _valueInstantiator, (JsonDeserializer<Object>) dd, unwrapSingle);
+                _valueInstantiator, (JsonDeserializer<Object>) dd,
+                nuller, unwrapSingle);
     }
 
     /**
@@ -135,7 +146,7 @@ protected CollectionDeserializer withResolved(JsonDeserializer<?> dd,
     protected CollectionDeserializer withResolved(JsonDeserializer<?> dd,
             JsonDeserializer<?> vd, TypeDeserializer vtd)
     {
-        return withResolved(dd, vd, vtd, _unwrapSingle);
+        return withResolved(dd, vd, vtd, vd, _unwrapSingle);
     }
 
     // Important: do NOT cache if polymorphic values
@@ -212,7 +223,9 @@ public CollectionDeserializer createContextual(DeserializationContext ctxt,
                 || (valueDeser != _valueDeserializer)
                 || (valueTypeDeser != _valueTypeDeserializer)
         ) {
-            return withResolved(delegateDeser, valueDeser, valueTypeDeser, unwrapSingle);
+            return withResolved(delegateDeser, valueDeser, valueTypeDeser,
+                    findContentNullProvider(ctxt, property, valueDeser),
+                    unwrapSingle);
         }
         return this;
     }
@@ -293,7 +306,7 @@ public Collection<Object> deserialize(JsonParser p, DeserializationContext ctxt,
             try {
                 Object value;
                 if (t == JsonToken.VALUE_NULL) {
-                    value = valueDes.getNullValue(ctxt);
+                    value = _nullProvider.getNullValue(ctxt);
                 } else if (typeDeser == null) {
                     value = valueDes.deserialize(p, ctxt);
                 } else {
@@ -356,7 +369,7 @@ protected final Collection<Object> handleNonArray(JsonParser p, DeserializationC
 
         try {
             if (t == JsonToken.VALUE_NULL) {
-                value = valueDes.getNullValue(ctxt);
+                value = _nullProvider.getNullValue(ctxt);
             } else if (typeDeser == null) {
                 value = valueDes.deserialize(p, ctxt);
             } else {