Throw exception if a user is trying to overwrite the data without first loading it

src/VirtualColumn.php

@@ -31,9 +31,11 @@ trait VirtualColumn
      */
     public bool $dataEncoded = false;
 
+    public bool $dataNotLoaded = false;
+
     protected function decodeVirtualColumn(): void
     {
-        if (! $this->dataEncoded) {
+        if (! $this->dataEncoded || ! $this->dataNotLoaded) {
             return;
         }
 
@@ -65,6 +67,10 @@ trait VirtualColumn
             return;
         }
 
+        if ($this->dataNotLoaded) {
+            throw new \Exception('Data column was not loaded from the database. Make sure the data column is selected in the query.');
+        }
+
         $dataColumn = static::getDataColumn();
         $customColumns = static::getCustomColumns();
         $attributes = array_filter($this->getAttributes(), fn ($key) => ! in_array($key, $customColumns), ARRAY_FILTER_USE_KEY);
@@ -107,11 +113,14 @@ trait VirtualColumn
         return [
             'retrieved' => [
                 function () {
+                    // If the data column wasn't retrieved, don't decode it
                     if (($this->attributes[static::getDataColumn()] ?? null) === null) {
+                        $this->dataNotLoaded = true;
+
                         return;
                     }
 
-                    // Always decode after model retrieval
+                    // Mark the data as encoded so that it doesn't get encoded again
                     $this->dataEncoded = true;
 
                     $this->decodeVirtualColumn();

tests/VirtualColumnTest.php

@@ -128,6 +128,20 @@ class VirtualColumnTest extends TestCase
         $this->assertSame($encodedBar->bar, 'bar');
     }
 
+    /** @test */
+    public function model_doesnt_overwrite_when_selectively_fetching() {
+        $this->expectExceptionMessage('Data column was not loaded from the database. Make sure the data column is selected in the query.');
+
+        FooModel::create([
+            'id' => 1,
+            'foo' => 'bar'
+        ]);
+
+        $foo = FooModel::query()->first(['id']);
+        $foo->bar = 'baz';
+        $foo->save();
+    }
+
     /** @test */
     public function decoding_works_with_strict_mode_enabled() {
         FooModel::shouldBeStrict();