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

- fix backward incompatibility

Author: cpartica

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

@@ -162,7 +162,10 @@ public function getExcludes($contentType)
     private function getMinificationExcludeValues($key)
     {
         $configValues = $this->scopeConfig->getValue($key, $this->scope) ?? [];
-
+        //compatibility fix for type change from string to array
+        if (!is_array($configValues)) {
+            $configValues = [$configValues => $configValues];
+        }
         return array_values($configValues);
     }
 }

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

@@ -195,6 +195,8 @@ public function isMinifiedFilenameDataProvider()
     }
 
     /**
+     * Test dev/js/minify_exclude system value as array
+     *
      * @return void
      */
     public function testGetExcludes()
@@ -213,4 +215,23 @@ public function testGetExcludes()
         /** check cache: */
         $this->assertEquals($expected, $this->minification->getExcludes('js'));
     }
+
+    /**
+     * Test dev/js/minify_exclude system value backward compatibility when value was a string
+     *
+     * @return void
+     */
+    public function testGetExcludesTinyMceAsString()
+    {
+        $this->scopeConfigMock
+            ->expects($this->once())
+            ->method('getValue')
+            ->with('dev/js/minify_exclude')
+            ->willReturn('/tiny_mce/');
+
+        $expected = ['/tiny_mce/'];
+        $this->assertEquals($expected, $this->minification->getExcludes('js'));
+        /** check cache: */
+        $this->assertEquals($expected, $this->minification->getExcludes('js'));
+    }
 }