Throw an exception for invalid "resultForIdenticals"

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

README.md

@@ -92,7 +92,7 @@ $rendererOptions = [
     // internally, ops (tags) are all int type but this is not good for human reading.
     // set this to "true" to convert them into string form before outputting.
     'outputTagAsString' => true,
-    // change this value to a non-null one as the the returned diff
+    // change this value to a string as the the returned diff
     // if the two input strings are identical
     'resultForIdenticals' => null,
     // extra HTML classes added to the DOM of the diff container

example/demo.php

@@ -48,7 +48,7 @@
             // internally, ops (tags) are all int type but this is not good for human reading.
             // set this to "true" to convert them into string form before outputting.
             'outputTagAsString' => false,
-            // change this value to a non-null one as the the returned diff
+            // change this value to a string as the the returned diff
             // if the two input strings are identical
             'resultForIdenticals' => null,
             // extra HTML classes added to the DOM of the diff container

src/Renderer/AbstractRenderer.php

@@ -49,7 +49,7 @@ abstract class AbstractRenderer implements RendererInterface
         // internally, ops (tags) are all int type but this is not good for human reading.
         // set this to "true" to convert them into string form before outputting.
         'outputTagAsString' => false,
-        // change this value to a non-null one as the the returned diff
+        // change this value to a string as the the returned diff
         // if the two input strings are identical
         'resultForIdenticals' => null,
         // extra HTML classes added to the DOM of the diff container
@@ -111,10 +111,20 @@ public function getOptions(): array
      * @final
      *
      * @todo mark this method with "final" in the next major release
+     *
+     * @throws \InvalidArgumentException
      */
     public function getResultForIdenticals(): string
     {
-        return $this->options['resultForIdenticals'] ?? $this->getResultForIdenticalsDefault();
+        $custom = $this->options['resultForIdenticals'];
+
+        if (isset($custom) && !\is_string($custom)) {
+            throw new \InvalidArgumentException(
+                'renderer option `resultForIdenticals` must be null or string.'
+            );
+        }
+
+        return $custom ?? $this->getResultForIdenticalsDefault();
     }
 
     /**

tests/Renderer/RendererTest.php

@@ -68,4 +68,22 @@ public function testSetOptionsWithResultForIdenticals(): void
             'Rederer options: result for identicals should work.'
         );
     }
+
+    /**
+     * Test the AbstractRenderer::setOptions with an invalid result for identicals.
+     *
+     * @covers \Jfcherng\Diff\Renderer\AbstractRenderer::setOptions
+     */
+    public function testSetOptionsWithInvalidResultForIdenticals(): void
+    {
+        static::expectException(\InvalidArgumentException::class);
+
+        $diffResult = DiffHelper::calculate(
+            'we are the same',
+            'we are the same',
+            'Inline',
+            [],
+            ['resultForIdenticals' => 50]
+        );
+    }
 }