Ensure fromDb() is idempotent for all behaviors

src/Behavior/MillisecondTimestamp.php

@@ -12,11 +12,11 @@
 {
     public function fromDb($value, $key, $context)
     {
-        if ($value === null) {
-            return null;
+        if ($value === null || $value instanceof DateTime) {
+            return $value;
         }
 
         $datetime = DateTime::createFromFormat('U.u', sprintf('%F', $value / 1000.0));
         $datetime->setTimezone(new DateTimeZone(date_default_timezone_get()));
 
         return $datetime;

src/Behavior/UUID.php

@@ -20,12 +20,12 @@
 
     public function fromDb($value, $key, $_)
     {
-        if ($value === null) {
-            return null;
+        if ($value === null || $value instanceof UuidInterface) {
+            return $value;
         }
 
         if (! is_string($value)) {
             throw new UnexpectedValueException(sprintf("Unexpected value '%s' for key '%s'", $value, $key));
         }
 
         try {
@@ -47,7 +47,7 @@
 
         if (! $value instanceof UuidInterface) {
             if (! is_string($value)) {
                 throw new UnexpectedValueException(sprintf("Unexpected value '%s' for key '%s'", $value, $key));
             }
 
             try {

tests/Behavior/UUIDTest.php

@@ -38,6 +38,22 @@ public function testRetrievePropertyReturnsUuidInstance(): void
         );
     }
 
+    public function testRetrievePropertyCanBeAppliedRepeatedly(): void
+    {
+        $behavior = $this->behavior();
+        $uuid = $behavior->retrieveProperty(
+            RamseyUuid::fromString(static::TEST_UUID_VALUE)->getBytes(),
+            static::TEST_COLUMN
+        );
+
+        $this->assertSame($uuid, $behavior->retrieveProperty($uuid, static::TEST_COLUMN));
+
+        $behavior = $this->behavior(true);
+        $uuid = $behavior->retrieveProperty(static::TEST_UUID_VALUE, static::TEST_COLUMN);
+
+        $this->assertSame($uuid, $behavior->retrieveProperty($uuid, static::TEST_COLUMN));
+    }
+
     public function testPersistPropertyReturnsNullWhenValueIsNull(): void
     {
         $this->assertNull($this->behavior()->persistProperty(null, static::TEST_COLUMN));

tests/MillisecondTimestampBehaviorTest.php

@@ -15,6 +15,14 @@ public function testFromDbReturnsNullWhenNullIsPassed()
         $this->assertNull((new MillisecondTimestamp([]))->fromDb(null, 'key', null));
     }
 
+    public function testFromDbCanBeAppliedRepeatedly()
+    {
+        $behavior = new MillisecondTimestamp([]);
+        $sometime = $behavior->fromDb(1668002400123, 'key', null);
+
+        $this->assertSame($sometime, $behavior->fromDb($sometime, 'key', null));
+    }
+
     public function testToDbReturnsNullWhenNullIsPassed()
     {
         $this->assertNull((new MillisecondTimestamp([]))->toDb(null, 'key', null));