Fix #5292: support "iPhone params" for Constructors too (#5311)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -4,6 +4,12 @@ Project: jackson-databind
 === Releases === 
 ------------------------------------------------------------------------
 
+2.20.1 (not yet released)
+
+#5292: `MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX` does not work with
+  Constructor parameters
+ (reported by @bananayong)
+
 2.20.0 (28-Aug-2025)
 
 #2678: `@JacksonInject` added to property overrides value from the JSON

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

@@ -1348,20 +1348,22 @@ protected void _fixLeadingFieldNameCase(Map<String, POJOPropertyBuilder> props)
 
         // First: find possible candidates where:
         //
-        // 1. Property only has Field
-        // 2. Field does NOT have explicit name (renaming)
-        // 3. Implicit name has upper-case for first and/or second character
+        // 1. Property has Field and/or Constructor Parameter
+        // 2. Property has no other accessors (no getters/setters)
+        // 3. Field/Constructor param does NOT have explicit name (renaming)
+        // 4. Implicit name has upper-case for first and/or second character
 
         Map<String, POJOPropertyBuilder> fieldsToCheck = null;
         for (Map.Entry<String, POJOPropertyBuilder> entry : props.entrySet()) {
             POJOPropertyBuilder  prop = entry.getValue();
 
-            // First: (1) and (2)
-            if (!prop.hasFieldAndNothingElse()
-                    || prop.isExplicitlyNamed()) {
+            // First: (1), (2) and 3
+            if (prop.isExplicitlyNamed() // (3)
+                    || !(prop.hasField() || prop.hasConstructorParameter()) // (1)
+                    || (prop.hasGetter() || prop.hasSetter())) { // 2
                 continue;
             }
-            // Second: (3)
+            // Second: (4)
             if (!_firstOrSecondCharUpperCase(entry.getKey())) {
                 continue;
             }

src/test/java/com/fasterxml/jackson/databind/misc/IPhoneStyleProperty5292Test.java

@@ -0,0 +1,106 @@
+package com.fasterxml.jackson.databind.misc;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonPropertyOrder;
+
+import com.fasterxml.jackson.databind.MapperFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.databind.testutil.DatabindTestUtil;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+// [databind#5292] Need support for creators `MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX`
+public class IPhoneStyleProperty5292Test
+    extends DatabindTestUtil
+{
+    static class AppleSingleNonTarget {
+        private final String name;
+
+        public AppleSingleNonTarget(@ImplicitName("name") String name) {
+            this.name = name;
+        }
+
+        public String getName() {
+            return name;
+        }
+    }
+
+    static class AppleSingleIsTarget {
+        private final String iPhone;
+
+        @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+        public AppleSingleIsTarget(@ImplicitName("iPhone") String iPhone) {
+            this.iPhone = iPhone;
+        }
+
+        public String getIPhone() {
+            return iPhone;
+        }
+    }
+
+    // Creator order should be used but just in case, define explicit order
+    @JsonPropertyOrder({ "iPhone", "name" })
+    static class AppleDouble {
+        private final String _iphone;
+        private final String name;
+
+        public AppleDouble(@ImplicitName("iPhone") String iPhone,
+                @ImplicitName("name") String name) {
+            this._iphone = iPhone;
+            this.name = name;
+        }
+
+        public String getIPhone() {
+            return _iphone;
+        }
+
+        public String getName() {
+            return name;
+        }
+    }
+
+    private final ObjectMapper MAPPER = JsonMapper.builder()
+        .annotationIntrospector(new ImplicitNameIntrospector())
+        .enable(MapperFeature.FIX_FIELD_NAME_UPPER_CASE_PREFIX)
+        .build();
+
+    @Test
+    public void testDeserDouble() throws Exception
+    {
+        AppleDouble apple = new AppleDouble("iPhone 15", "Jay");
+        String json = MAPPER.writeValueAsString(apple);
+        assertEquals("{\"iPhone\":\"iPhone 15\",\"name\":\"Jay\"}", json);
+
+        AppleDouble result = MAPPER.readValue(json, AppleDouble.class); // Error thrown
+
+        assertEquals("Jay", result.getName());
+        assertEquals("iPhone 15", result.getIPhone());
+    }
+
+
+    @Test
+    public void testSingleArgCase() throws Exception
+    {
+        AppleSingleIsTarget apple = new AppleSingleIsTarget("iPhone 15");
+        String json = MAPPER.writeValueAsString(apple);
+        assertEquals("{\"iPhone\":\"iPhone 15\"}", json);
+
+        AppleSingleIsTarget result = MAPPER.readValue(json, AppleSingleIsTarget.class);
+        assertEquals("iPhone 15", result.getIPhone());
+    }
+
+    // Just for comparison
+    @Test
+    public void testHappyCaseSingleArgString() throws Exception
+    {
+        AppleSingleNonTarget apple = new AppleSingleNonTarget("Jay");
+        String json = MAPPER.writeValueAsString(apple);
+        assertEquals("{\"name\":\"Jay\"}", json);
+
+        AppleSingleNonTarget result = MAPPER.readValue(json, AppleSingleNonTarget.class);
+        assertEquals("Jay", result.getName());
+    }
+}