Work on #2527

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

@@ -614,6 +614,42 @@ public AnnotatedMethod resolveSetterConflict(MapperConfig<?> config,
         return null;
     }
 
+    /**
+     * Method called on fields that are eligible candidates for properties
+     * (that is, non-static member fields), but not necessarily selected (may
+     * or may not be visible), to let fields affect name linking.
+     * Call will be made after finding implicit name (which by default is just
+     * name of the field, but may be overridden by introspector), but before
+     * discovering other accessors.
+     * If non-null name returned, it is to be used to find other accessors (getters,
+     * setters, creator parameters) and replace their implicit names with that
+     * of field's implicit name (assuming they differ).
+     *<p>
+     * Specific example (and initial use case is for support Kotlin's "is getter"
+     * matching (see
+     * <a href="https://kotlinlang.org/docs/reference/java-to-kotlin-interop.html">Kotling Interop</a>
+     * for details), in which field like '{@code isOpen}' would have implicit name of
+     * "isOpen", match getter {@code getOpen()} and setter {@code setOpen(boolean)},
+     * but use logical external name of "isOpen" (and not implicit name of getter/setter, "open"!).
+     * To achieve this, field implicit name needs to remain "isOpen" but this method needs
+     * to return name {@code PropertyName.construct("open")}: doing so will "pull in" getter
+     * and/or setter, and rename them as "isOpen".
+     *
+     * @param config Effective mapper configuration in use
+     * @param f Field to check
+     * @param implName Implicit name of the field; usually name of field itself but not always,
+     *    used as the target name for accessors to rename.
+     *
+     * @return Name used to find other accessors to rename, if any; {@code null} to indicate
+     *    no renaming
+     *
+     * @since 2.11
+     */
+    public PropertyName findRenameByField(MapperConfig<?> config,
+            AnnotatedField f, PropertyName implName) {
+        return null;
+    }
+
     /**
      * @deprecated Since 2.9 Use {@link #findInjectableValue} instead
      */

src/main/java/com/fasterxml/jackson/databind/introspect/AnnotationIntrospectorPair.java

@@ -520,6 +520,16 @@ public AnnotatedMethod resolveSetterConflict(MapperConfig<?> config,
         return res;
     }
 
+    @Override // since 2.11
+    public PropertyName findRenameByField(MapperConfig<?> config,
+            AnnotatedField f, PropertyName implName) {
+        PropertyName n = _secondary.findRenameByField(config, f, implName);
+        if (n == null) {
+            n = _primary.findRenameByField(config, f, implName);
+        }
+        return n;
+    }
+
     // // // Serialization: type refinements
 
     @Override // since 2.7

src/main/java/com/fasterxml/jackson/databind/introspect/JacksonAnnotationIntrospector.java

@@ -533,6 +533,13 @@ public AnnotatedMethod resolveSetterConflict(MapperConfig<?> config,
         return null;
     }
 
+    @Override // since 2.11
+    public PropertyName findRenameByField(MapperConfig<?> config,
+            AnnotatedField f, PropertyName implName) {
+        // Nothing to report, only used by modules. But define just as documentation
+        return null;
+    }
+
     /*
     /**********************************************************
     /* Annotations for Polymorphic Type handling

src/main/java/com/fasterxml/jackson/databind/introspect/POJOPropertiesCollector.java

@@ -314,6 +314,9 @@ protected void collectAll()
         }
         _addInjectables(props);
 
+        // 27-Dec-2019, tatu: [databind#2527] initial re-linking by Field needs to
+        //    be applied before other processing
+
         // Remove ignored properties, first; this MUST precede annotation merging
         // since logic relies on knowing exactly which accessor has which annotation
         _removeUnwantedProperties(props);
@@ -372,9 +375,8 @@ protected void _addFields(Map<String, POJOPropertyBuilder> props)
          */
         final boolean pruneFinalFields = !_forSerialization && !_config.isEnabled(MapperFeature.ALLOW_FINAL_FIELDS_AS_MUTATORS);
         final boolean transientAsIgnoral = _config.isEnabled(MapperFeature.PROPAGATE_TRANSIENT_MARKER);
-        
+
         for (AnnotatedField f : _classDef.fields()) {
-            String implName = ai.findImplicitPropertyName(f);
             // @JsonValue?
             if (Boolean.TRUE.equals(ai.hasAsValue(f))) {
                 if (_jsonValueAccessors == null) {
@@ -391,17 +393,26 @@ protected void _addFields(Map<String, POJOPropertyBuilder> props)
                 _anySetterField.add(f);
                 continue;
             }
+            String implName = ai.findImplicitPropertyName(f);
             if (implName == null) {
                 implName = f.getName();
             }
+
+            // [databind#2527: Field-based renaming can be applied early (here),
+            // or at a later point, but probably must be done before pruning
+            // final fields. So let's do it early here
+            final PropertyName rename = ai.findRenameByField(_config, f, _propNameFromSimple(implName));
+            if (rename != null) {
+                // todo
+            }
+
             PropertyName pn;
 
             if (_forSerialization) {
-                /* 18-Aug-2011, tatu: As per existing unit tests, we should only
-                 *   use serialization annotation (@JsonSerialize) when serializing
-                 *   fields, and similarly for deserialize-only annotations... so
-                 *   no fallbacks in this particular case.
-                 */
+                // 18-Aug-2011, tatu: As per existing unit tests, we should only
+                //   use serialization annotation (@JsonSerialize) when serializing
+                //   fields, and similarly for deserialize-only annotations... so
+                //   no fallbacks in this particular case.
                 pn = ai.findNameForSerialization(f);
             } else {
                 pn = ai.findNameForDeserialization(f);
@@ -434,7 +445,7 @@ protected void _addFields(Map<String, POJOPropertyBuilder> props)
             }
             /* [databind#190]: this is the place to prune final fields, if they are not
              *  to be used as mutators. Must verify they are not explicitly included.
-             *  Also: if 'ignored' is set, need to included until a later point, to
+             *  Also: if 'ignored' is set, need to include until a later point, to
              *  avoid losing ignoral information.
              */
             if (pruneFinalFields && (pn == null) && !ignored

src/main/java/com/fasterxml/jackson/databind/util/BeanUtil.java

@@ -260,9 +260,11 @@ protected static String legacyManglePropertyName(final String basename, final in
     }
 
     /**
+     * Note: public only since 2.11
+     *
      * @since 2.5
      */
-    protected static String stdManglePropertyName(final String basename, final int offset)
+    public static String stdManglePropertyName(final String basename, final int offset)
     {
         final int end = basename.length();
         if (end == offset) { // empty name, nope

src/test/java/com/fasterxml/jackson/failing/IsGetterRenaming2527Test.java

@@ -4,6 +4,10 @@
 import java.util.Map;
 
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.MapperConfig;
+import com.fasterxml.jackson.databind.introspect.AnnotatedField;
+import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
+import com.fasterxml.jackson.databind.util.BeanUtil;
 
 // [databind#2527] Support Kotlin-style "is" properties
 public class IsGetterRenaming2527Test extends BaseMapTest
@@ -20,9 +24,40 @@ public POJO2527(boolean b) {
         public void setEnabled(boolean b) { isEnabled = b; }
     }
 
+    static class POJO2527b {
+        public boolean isEnabled;
+
+        protected POJO2527b() { }
+        public POJO2527b(boolean b) {
+            isEnabled = b;
+        }
+
+        public boolean getEnabled() { return isEnabled; }
+        public void setEnabled(boolean b) { isEnabled = b; }
+    }
+
+    @SuppressWarnings("serial")
+    static class MyIntrospector extends JacksonAnnotationIntrospector
+    {
+        @Override
+        public PropertyName findRenameByField(MapperConfig<?> config,
+                AnnotatedField f, PropertyName implName)
+        {
+            final String origSimple = implName.getSimpleName();
+            if (origSimple.startsWith("is")) {
+                String mangledName = BeanUtil.stdManglePropertyName(origSimple, 2);
+                // Needs to be valid ("is" -> null), and different from original
+                if ((mangledName != null) && !mangledName.equals(origSimple)) {
+                    return PropertyName.construct(mangledName);
+                }
+            }
+            return null;
+        }
+    }
+
     private final ObjectMapper MAPPER = newJsonMapper();
 
-    public void testIsProperties() throws Exception
+    public void testIsPropertiesStdKotlin() throws Exception
     {
         POJO2527 input = new POJO2527(true);
         final String json = MAPPER.writeValueAsString(input);
@@ -34,4 +69,17 @@ public void testIsProperties() throws Exception
         POJO2527 output = MAPPER.readValue(json, POJO2527.class);
         assertEquals(input.isEnabled, output.isEnabled);
     }
+
+    public void testIsPropertiesAlt() throws Exception
+    {
+        POJO2527b input = new POJO2527b(true);
+        final String json = MAPPER.writeValueAsString(input);
+
+        Map<?, ?> props = MAPPER.readValue(json, Map.class);
+        assertEquals(Collections.singletonMap("isEnabled", Boolean.TRUE),
+                props);
+
+        POJO2527b output = MAPPER.readValue(json, POJO2527b.class);
+        assertEquals(input.isEnabled, output.isEnabled);
+    }
 }