Minor tweaking wrt #2978

Author: cowtowncoder

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

@@ -463,13 +463,15 @@ value, rewrapCtorProblem(ctxt, t)
         // with less precision as doubles. When written to a TokenBuffer for polymorphic
         // deserialization the most specific type is recorded, though a less precise
         // floating point value may be needed.
-        if(_fromDoubleCreator != null && canConvertToDouble(value)) {
-            Object arg = value.doubleValue();
-            try {
-                return _fromDoubleCreator.call1(arg);
-            } catch (Throwable t0) {
-                return ctxt.handleInstantiationProblem(_fromDoubleCreator.getDeclaringClass(),
-                        arg, rewrapCtorProblem(ctxt, t0));
+        if (_fromDoubleCreator != null) {
+            Double dbl = tryConvertToDouble(value);
+            if (dbl != null) {
+                try {
+                    return _fromDoubleCreator.call1(dbl);
+                } catch (Throwable t0) {
+                    return ctxt.handleInstantiationProblem(_fromDoubleCreator.getDeclaringClass(),
+                            dbl, rewrapCtorProblem(ctxt, t0));
+                }
             }
         }
 
@@ -478,9 +480,11 @@ value, rewrapCtorProblem(ctxt, t)
 
     // BigDecimal cannot represent special values NaN, positive infinity, or negative infinity.
     // When the value cannot be represented as a double, positive or negative infinity is returned.
-    static boolean canConvertToDouble(BigDecimal value) {
+    //
+    // @since 2.12.1
+    static Double tryConvertToDouble(BigDecimal value) {
         double doubleValue = value.doubleValue();
-        return !Double.isInfinite(doubleValue);
+        return Double.isInfinite(doubleValue) ? null : doubleValue;
     }
 
     @Override

src/test/java/com/fasterxml/jackson/databind/deser/std/StdValueInstantiatorTest.java

@@ -4,17 +4,18 @@
 
 import java.math.BigDecimal;
 
-public class StdValueInstantiatorTest extends BaseMapTest {
-
+// [databind#2978]
+public class StdValueInstantiatorTest extends BaseMapTest
+{
     public void testDoubleValidation_valid() {
-        assertTrue(StdValueInstantiator.canConvertToDouble(BigDecimal.ZERO));
-        assertTrue(StdValueInstantiator.canConvertToDouble(BigDecimal.ONE));
-        assertTrue(StdValueInstantiator.canConvertToDouble(BigDecimal.TEN));
-        assertTrue(StdValueInstantiator.canConvertToDouble(BigDecimal.valueOf(-1.5D)));
+        assertEquals(0d, StdValueInstantiator.tryConvertToDouble(BigDecimal.ZERO));
+        assertEquals(1d, StdValueInstantiator.tryConvertToDouble(BigDecimal.ONE));
+        assertEquals(10d, StdValueInstantiator.tryConvertToDouble(BigDecimal.TEN));
+        assertEquals(-1.5d, StdValueInstantiator.tryConvertToDouble(BigDecimal.valueOf(-1.5d)));
     }
 
     public void testDoubleValidation_invalid() {
         BigDecimal value = BigDecimal.valueOf(Double.MAX_VALUE).add(BigDecimal.valueOf(Double.MAX_VALUE));
-        assertFalse(StdValueInstantiator.canConvertToDouble(value));
+        assertNull(StdValueInstantiator.tryConvertToDouble(value));
     }
-}
+}

src/test/java/com/fasterxml/jackson/databind/jsontype/TestDoubleJsonCreator.java

@@ -12,15 +12,17 @@
 import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
 
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
-public class TestDoubleJsonCreator extends BaseMapTest  {
-
-    public static final class UnionExample {
+// For [databind#2978]
+public class TestDoubleJsonCreator extends BaseMapTest
+{
+    static final class UnionExample {
         private final Base value;
 
         @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
@@ -78,7 +80,7 @@ private static final class DoubleWrapper implements Base {
             private final AliasDouble value;
 
             @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
-            private DoubleWrapper(@JsonSetter("double") AliasDouble value) {
+            DoubleWrapper(@JsonSetter("double") AliasDouble value) {
                 Objects.requireNonNull(value, "double cannot be null");
                 this.value = value;
             }
@@ -176,7 +178,7 @@ public String toString() {
         }
     }
 
-    public static final class AliasDouble {
+    static final class AliasDouble {
         private final double value;
 
         private AliasDouble(double value) {
@@ -211,17 +213,21 @@ public static AliasDouble of(double value) {
         }
     }
 
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    // [databind#2978]
     public void testDeserializationTypeFieldLast() throws IOException {
         UnionExample expected = UnionExample.double_(AliasDouble.of(2.0D));
-        UnionExample actual = objectMapper().readValue(
+        UnionExample actual = MAPPER.readValue(
                 a2q("{'double': 2.0,'type':'double'}"),
                 new TypeReference<UnionExample>() {});
         assertEquals(expected, actual);
     }
 
+    // [databind#2978]
     public void testDeserializationTypeFieldFirst() throws IOException {
         UnionExample expected = UnionExample.double_(AliasDouble.of(2.0D));
-        UnionExample actual = objectMapper().readValue(
+        UnionExample actual = MAPPER.readValue(
                 a2q("{'type':'double','double': 2.0}"),
                 new TypeReference<UnionExample>() {});
         assertEquals(expected, actual);