MAGETWO-93305: Broken upgrade to 2.3 due to changed data type for minify_exclude

- adding multi value string support divided by \n

Author: cpartica

lib/internal/Magento/Framework/View/Asset/Minification.php

@@ -162,9 +162,9 @@ public function getExcludes($contentType)
     private function getMinificationExcludeValues($key)
     {
         $configValues = $this->scopeConfig->getValue($key, $this->scope) ?? [];
-        //compatibility fix for type change from string to array
+        //compatibility fix for type change from new line separated string values to array
         if (!is_array($configValues)) {
-            $configValues = [$configValues => $configValues];
+            $configValues = explode("\n", $configValues);
         }
         return array_values($configValues);
     }

lib/internal/Magento/Framework/View/Test/Unit/Asset/MinificationTest.php

@@ -219,19 +219,34 @@ public function testGetExcludes()
     /**
      * Test dev/js/minify_exclude system value backward compatibility when value was a string
      *
+     * @param string $value
+     * @param array $expectedValue
      * @return void
+     *
+     * @dataProvider getExcludesTinyMceAsStringDataProvider
      */
-    public function testGetExcludesTinyMceAsString()
+    public function testGetExcludesTinyMceAsString(string $value, array $expectedValue)
     {
         $this->scopeConfigMock
             ->expects($this->once())
             ->method('getValue')
             ->with('dev/js/minify_exclude')
-            ->willReturn('/tiny_mce/');
+            ->willReturn($value);
 
-        $expected = ['/tiny_mce/'];
-        $this->assertEquals($expected, $this->minification->getExcludes('js'));
+        $this->assertEquals($expectedValue, $this->minification->getExcludes('js'));
         /** check cache: */
-        $this->assertEquals($expected, $this->minification->getExcludes('js'));
+        $this->assertEquals($expectedValue, $this->minification->getExcludes('js'));
+    }
+
+
+    /**
+     * @return array
+     */
+    public function getExcludesTinyMceAsStringDataProvider()
+    {
+        return [
+            ["/tiny_mce/\n/tiny_mce2/", ['/tiny_mce/', '/tiny_mce2/']],
+            ['/tiny_mce/', ['/tiny_mce/']],
+        ];
     }
 }