[8.x] Add foreignKey and localKey to query if they are missing

src/Illuminate/Database/Eloquent/Relations/HasOneOrMany.php

@@ -422,4 +422,53 @@ public function getLocalKeyName()
     {
         return $this->localKey;
     }
+
+    /**
+     * Since eager loading returns empty relationship collections
+     * when foreignKey or localKey are missing, make sure, they are
+     * included in the $columns array.
+     *
+     * @param  array  $columns
+     * @return  array
+     */
+    protected function ensureKeyExistence($columns = ['*'])
+    {
+        if ($columns !== ['*'] && ! in_array($this->foreignKey, $columns)) {
+            $columns[] = $this->foreignKey;
+        }
+
+        if ($columns !== ['*'] && ! in_array($this->localKey, $columns)) {
+            $columns[] = $this->localKey;
+        }
+
+        return $columns;
+    }
+
+    /**
+     * Execute the query as a "select" statement.
+     *
+     * @param  array  $columns
+     * @return \Illuminate\Database\Eloquent\Collection
+     */
+    public function get($columns = ['*'])
+    {
+        $columns = $this->ensureKeyExistence($columns);
+
+        return parent::get($columns);
+    }
+
+    /**
+     * Set the columns to be selected.
+     *
+     * @param  array|mixed  $columns
+     * @return $this
+     */
+    public function select($columns = ['*'])
+    {
+        $columns = $this->ensureKeyExistence($columns);
+
+        parent::select($columns);
+
+        return $this;
+    }
 }

tests/Integration/Database/EloquentCollectionLoadMissingTest.php

@@ -79,7 +79,7 @@ public function testLoadMissing()
         $this->assertCount(2, DB::getQueryLog());
         $this->assertTrue($posts[0]->comments[0]->relationLoaded('parent'));
         $this->assertTrue($posts[0]->comments[1]->parent->relationLoaded('revisions'));
-        $this->assertArrayNotHasKey('id', $posts[0]->comments[1]->parent->revisions[0]->getAttributes());
+        $this->assertArrayHasKey('id', $posts[0]->comments[1]->parent->revisions[0]->getAttributes());
     }
 
     public function testLoadMissingWithClosure()