Fix #2894

Author: cowtowncoder

release-notes/CREDITS-2.x

@@ -1159,3 +1159,7 @@ Nils Christian Ehmke (nils-christian@github)
 Daniel Wu (DanielYWoo@github)
   * Reported #2840: `ObjectMapper.activateDefaultTypingAsProperty()` is not using
   (2.11.3)
+
+Łukasz Walkiewicz (lukasz-walkiewicz@github)
+  * Reported #2894: Fix type resolution for static methods (regression in 2.11.3)
+  (2.11.4)

release-notes/VERSION-2.x

@@ -4,6 +4,11 @@ Project: jackson-databind
 === Releases === 
 ------------------------------------------------------------------------
 
+2.11.4 (not yet released)
+
+#2894: Fix type resolution for static methods (regression in 2.11.3)
+ (reported by Łukasz W)
+
 2.11.3 (02-Oct-2020)
 
 #2795: Cannot detect creator arguments of mixins for JDK types

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

@@ -226,7 +226,12 @@ private List<AnnotatedMethod> _findPotentialFactories(JavaType type, Class<?> pr
         //   passing that should not break things, it appears to... Regardless,
         //   it should not be needed or useful as those bindings are only available
         //   to non-static members
-        TypeResolutionContext typeResCtxt = new TypeResolutionContext.Empty(_typeFactory);
+
+        // 27-Oct-2020, tatu: SIGH. As per [databind#2894] there is widespread use of
+        //   incorrect bindings in the wild -- not supported (no tests) but used
+        //   nonetheless. So, for 2.11.x, put back "Bad Bindings"...
+//        final TypeResolutionContext typeResCtxt = new TypeResolutionContext.Empty(_typeFactory);
+        final TypeResolutionContext typeResCtxt = _typeContext;
 
         int factoryCount = candidates.size();
         List<AnnotatedMethod> result = new ArrayList<>(factoryCount);

src/test/java/com/fasterxml/jackson/databind/deser/creators/broken/Pre212StaticFactoryImplicitBindingTest.java

@@ -0,0 +1,68 @@
+package com.fasterxml.jackson.databind.deser.creators.broken;
+
+import java.util.Arrays;
+import java.util.List;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.*;
+
+// Test(s) to check for handling of Static Factory Creator bindings
+// which up until 2.11.2 used type variable bindings of the surrounding
+// class for Static methods too. This is semantically wrong, but quite a
+// bit of usage existed -- but no one had contributed tests to verify
+// this as expected behavior.
+// When this usage broken in 2.11.3 -- it was never actually supported but
+// happened to sort of work -- reports came in. This test verifies
+// assumed behavior so that previous broken (but useful) bindings could
+// be brought back for 2.11.4.
+//
+// Work for 2.12 should find better solution than this.
+
+public class Pre212StaticFactoryImplicitBindingTest extends BaseMapTest
+{
+    // [databind#2894]
+    static class Wrapper<T> {
+        List<T> values;
+
+        protected Wrapper(List<T> v) {
+            values = v;
+        }
+
+        public List<T> getValue() { return values; }
+
+        @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
+        static <T> Wrapper<T> fromValues(@JsonProperty("value") List<T> values) {
+          return new Wrapper<T>(values);
+        }
+    }
+
+    static class Value {
+        public int x;
+
+        protected Value() { }
+        protected Value(int x0) { x = x0; }
+
+        @Override
+        public boolean equals(Object o) {
+            return (o instanceof Value) && ((Value) o).x == x;
+        }
+
+        @Override
+        public String toString() {
+            return "[Value x="+x+"]";
+        }
+    }
+
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    public void testIssue2894() throws Exception
+    {
+        Wrapper<Value> src = new Wrapper<>(Arrays.asList(new Value(1), new Value(2)));
+        final String json = MAPPER.writeValueAsString(src);
+        Wrapper<Value> output = MAPPER.readValue(json,
+                new TypeReference<Wrapper<Value>>() {});
+        assertEquals(src.values, output.values);
+    }
+}