Rewrote handling of "empty array to null" coercion, using CoercionConfigs (needs more testing)

3 files changed, 85 insertions, 63 deletions

diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java
index e94891ac4..ced28f0a9 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java
@@ -5,6 +5,7 @@ import java.util.*;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.CoercionAction;
 import com.fasterxml.jackson.databind.deser.impl.*;
 import com.fasterxml.jackson.databind.deser.impl.ReadableObjectId.Referring;
 import com.fasterxml.jackson.databind.util.NameTransformer;
@@ -583,23 +584,29 @@ public class BeanDeserializer
             }
             return bean;
         }
-        if (ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)) {
-            JsonToken t = p.nextToken();
-            if (t == JsonToken.END_ARRAY && ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
-                return null;
-            }
-            final Object value = deserialize(p, ctxt);
-            if (p.nextToken() != JsonToken.END_ARRAY) {
-                handleMissingEndArrayForSingle(p, ctxt);
-            }
-            return value;
-        }
-        if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
+        final CoercionAction act = _findCoercionFromEmptyArray(ctxt);
+        final boolean unwrap = ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
+
+        if (unwrap || (act != CoercionAction.Fail)) {
             JsonToken t = p.nextToken();
             if (t == JsonToken.END_ARRAY) {
-                return null;
+                switch (act) {
+                case AsEmpty:
+                    return getEmptyValue(ctxt);
+                case AsNull:
+                case TryConvert:
+                    return getNullValue(ctxt);
+                default:
+                }
+                return ctxt.handleUnexpectedToken(getValueType(ctxt), JsonToken.START_ARRAY, p, null);
+            }
+            if (unwrap) {
+                final Object value = deserialize(p, ctxt);
+                if (p.nextToken() != JsonToken.END_ARRAY) {
+                    handleMissingEndArrayForSingle(p, ctxt);
+                }
+                return value;
             }
-            return ctxt.handleUnexpectedToken(getValueType(ctxt), JsonToken.START_ARRAY, p, null);
         }
         return ctxt.handleUnexpectedToken(getValueType(ctxt), p);
     }
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/BuilderBasedDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/BuilderBasedDeserializer.java
index 295de3179..fa15ed319 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/BuilderBasedDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/BuilderBasedDeserializer.java
@@ -5,6 +5,7 @@ import java.util.*;
 
 import com.fasterxml.jackson.core.*;
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.CoercionAction;
 import com.fasterxml.jackson.databind.deser.impl.*;
 import com.fasterxml.jackson.databind.introspect.AnnotatedMethod;
 import com.fasterxml.jackson.databind.util.NameTransformer;
@@ -492,23 +493,29 @@ public class BuilderBasedDeserializer
             }
             return finishBuild(ctxt, builder);
         }
-        if (ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)) {
-            JsonToken t = p.nextToken();
-            if (t == JsonToken.END_ARRAY && ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
-                return null;
-            }
-            final Object value = deserialize(p, ctxt);
-            if (p.nextToken() != JsonToken.END_ARRAY) {
-                handleMissingEndArrayForSingle(p, ctxt);
-            }
-            return value;
-        }
-        if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
+        final CoercionAction act = _findCoercionFromEmptyArray(ctxt);
+        final boolean unwrap = ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
+
+        if (unwrap || (act != CoercionAction.Fail)) {
             JsonToken t = p.nextToken();
             if (t == JsonToken.END_ARRAY) {
-                return null;
+                switch (act) {
+                case AsEmpty:
+                    return getEmptyValue(ctxt);
+                case AsNull:
+                case TryConvert:
+                    return getNullValue(ctxt);
+                default:
+                }
+                return ctxt.handleUnexpectedToken(getValueType(ctxt), JsonToken.START_ARRAY, p, null);
+            }
+            if (unwrap) {
+                final Object value = deserialize(p, ctxt);
+                if (p.nextToken() != JsonToken.END_ARRAY) {
+                    handleMissingEndArrayForSingle(p, ctxt);
+                }
+                return value;
             }
-            return ctxt.handleUnexpectedToken(getValueType(ctxt), JsonToken.START_ARRAY, p, null);
         }
         return ctxt.handleUnexpectedToken(getValueType(ctxt), p);
     }
diff --git a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDeserializer.java b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDeserializer.java
index 3f88e9430..c575dd65b 100644
--- a/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDeserializer.java
+++ b/src/main/java/com/fasterxml/jackson/databind/deser/std/StdDeserializer.java
@@ -51,12 +51,11 @@ public abstract class StdDeserializer<T>
             DeserializationFeature.USE_BIG_INTEGER_FOR_INTS.getMask()
             | DeserializationFeature.USE_LONG_FOR_INTS.getMask();
 
-    // @since 2.9
+    @Deprecated // since 2.12
     protected final static int F_MASK_ACCEPT_ARRAYS =
             DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS.getMask() |
             DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT.getMask();
 
-
     /**
      * Type of values this deserializer handles: sometimes
      * exact types, other time most specific supertype of
@@ -179,11 +178,11 @@ public abstract class StdDeserializer<T>
      */
 
     /**
-     * Helper method that allows easy support for array-related {@link DeserializationFeature}s
-     * `ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT` and `UNWRAP_SINGLE_VALUE_ARRAYS`: checks for either
-     * empty array, or single-value array-wrapped value (respectively), and either reports
-     * an exception (if no match, or feature(s) not enabled), or returns appropriate
-     * result value.
+     * Helper method that allows easy support for array-related coercion features:
+     * checks for either empty array, or single-value array-wrapped value (if coercion
+     * enabled by {@code CoercionConfigs} (since 2.12), and either reports
+     * an exception (if no coercion allowed), or returns appropriate
+     * result value using coercion mechanism indicated.
      *<p>
      * This method should NOT be called if Array representation is explicitly supported
      * for type: it should only be called in case it is otherwise unrecognized.
@@ -194,29 +193,32 @@ public abstract class StdDeserializer<T>
      *
      * @since 2.9
      */
+    @SuppressWarnings("unchecked")
     protected T _deserializeFromArray(JsonParser p, DeserializationContext ctxt) throws IOException
     {
-        JsonToken t;
-        if (ctxt.hasSomeOfFeatures(F_MASK_ACCEPT_ARRAYS)) {
-            t = p.nextToken();
+        final CoercionAction act = _findCoercionFromEmptyArray(ctxt);
+        final boolean unwrap = ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
+
+        if (unwrap || (act != CoercionAction.Fail)) {
+            JsonToken t = p.nextToken();
             if (t == JsonToken.END_ARRAY) {
-                if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
+                switch (act) {
+                case AsEmpty:
+                    return (T) getEmptyValue(ctxt);
+                case AsNull:
+                case TryConvert:
                     return getNullValue(ctxt);
+                default:
                 }
-            }
-            if (ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)) {
+            } else if (unwrap) {
                 final T parsed = _deserializeWrappedValue(p, ctxt);
                 if (p.nextToken() != JsonToken.END_ARRAY) {
                     handleMissingEndArrayForSingle(p, ctxt);
                 }
                 return parsed;
             }
-        } else {
-            t = p.currentToken();
         }
-        @SuppressWarnings("unchecked")
-        T result = (T) ctxt.handleUnexpectedToken(getValueType(ctxt), p.currentToken(), p, null);
-        return result;
+        return (T) ctxt.handleUnexpectedToken(getValueType(ctxt), JsonToken.START_ARRAY, p, null);
     }
 
     /**
@@ -228,7 +230,7 @@ public abstract class StdDeserializer<T>
      * @deprecated Since 2.12
      */
     @SuppressWarnings("unchecked")
-    @Deprecated
+    @Deprecated // since 2.12
     protected T _deserializeFromEmpty(JsonParser p, DeserializationContext ctxt)
         throws IOException
     {
@@ -715,23 +717,27 @@ public abstract class StdDeserializer<T>
     protected java.util.Date _parseDateFromArray(JsonParser p, DeserializationContext ctxt)
             throws IOException
     {
-        JsonToken t;
-        if (ctxt.hasSomeOfFeatures(F_MASK_ACCEPT_ARRAYS)) {
-            t = p.nextToken();
+        final CoercionAction act = _findCoercionFromEmptyArray(ctxt);
+        final boolean unwrap = ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS);
+
+        if (unwrap || (act != CoercionAction.Fail)) {
+            JsonToken t = p.nextToken();
             if (t == JsonToken.END_ARRAY) {
-                if (ctxt.isEnabled(DeserializationFeature.ACCEPT_EMPTY_ARRAY_AS_NULL_OBJECT)) {
+                switch (act) {
+                case AsEmpty:
+                    return (java.util.Date) getEmptyValue(ctxt);
+                case AsNull:
+                case TryConvert:
                     return (java.util.Date) getNullValue(ctxt);
+                default:
                 }
-            }
-            if (ctxt.isEnabled(DeserializationFeature.UNWRAP_SINGLE_VALUE_ARRAYS)) {
+            } else if (unwrap) {
                 final Date parsed = _parseDate(p, ctxt);
                 _verifyEndArrayForSingle(p, ctxt);
                 return parsed;
             }
-        } else {
-            t = p.currentToken();
         }
-        return (java.util.Date) ctxt.handleUnexpectedToken(_valueClass, t, p, null);
+        return (java.util.Date) ctxt.handleUnexpectedToken(_valueClass, JsonToken.START_ARRAY, p, null);
     }
 
     /**
@@ -1327,18 +1333,20 @@ value, _coercedTypeDesc());
 
     // @since 2.12
     protected CoercionAction _findCoercionFromEmptyString(DeserializationContext ctxt) {
-        final Class<?> targetClass = handledType();
-        final LogicalType targetType = logicalType();
+        return ctxt.findCoercionAction(logicalType(), handledType(),
+                CoercionInputShape.EmptyString);
+    }
 
-        return ctxt.findCoercionAction(targetType, targetClass, CoercionInputShape.EmptyString);
+    // @since 2.12
+    protected CoercionAction _findCoercionFromEmptyArray(DeserializationContext ctxt) {
+        return ctxt.findCoercionAction(logicalType(), handledType(),
+                CoercionInputShape.EmptyArray);
     }
 
     // @since 2.12
     protected CoercionAction _findCoercionFromBlankString(DeserializationContext ctxt) {
-        final Class<?> targetClass = handledType();
-        final LogicalType targetType = logicalType();
-
-        return ctxt.findCoercionFromBlankString(targetType, targetClass, CoercionAction.Fail);
+        return ctxt.findCoercionFromBlankString(logicalType(), handledType(),
+                CoercionAction.Fail);
     }
 
     /*