[FEATURE] Add CssInliner::getMatchingUninlinableSelectors

Part of #380. The basic functionality of the method is unit-tested. More extensive unit tests involving all kinds CSS rules and HTML already exist for testing the full content of the `<style>` element containing the uninlinable rules.
MyIntervals · Sep 12, 2019 · eac5952 · eac5952
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## x.y.z
 
 ### Added
+- Add `CssInliner::getMatchingUninlinableSelectors`
+  ([#380](https://github.com/MyIntervals/emogrifier/issues/380),
+  [#707](https://github.com/MyIntervals/emogrifier/pull/707))
 - Add tests for `:nth-child` and `:nth-of-type`
   ([#71](https://github.com/MyIntervals/emogrifier/issues/71),
   [#698](https://github.com/MyIntervals/emogrifier/pull/698))

diff --git a/src/Emogrifier/CssInliner.php b/src/Emogrifier/CssInliner.php
@@ -626,6 +626,20 @@ private function attributeValueIsImportant($attributeValue)
         return \strtolower(\substr(\trim($attributeValue), -10)) === '!important';
     }
 
+    /**
+     * Gets the array of selectors present in the CSS provided to `inlineCss()` for which the declarations could not be
+     * applied as inline styles, but which may affect elements in the HTML.  The relevant CSS will have been placed in a
+     * `<style>` element.  The selectors may include those used within @media rules or those involving dynamic
+     * pseudo-classes (such as `:hover`) or pseudo-elements (such as `::after`).  `inlineCss()` must have been called
+     * first, otherwise an empty array is returned.
+     *
+     * @return string[]
+     */
+    public function getMatchingUninlinableSelectors()
+    {
+        return \array_column($this->matchingUninlinableCssRules, 'selector');
+    }
+
     /**
      * Determines which of `$cssRules` actually apply to `$this->domDocument`, and sets them in
      * `$this->matchingUninlinableCssRules`.

diff --git a/tests/Unit/CssInlinerTest.php b/tests/Unit/CssInlinerTest.php
@@ -2618,6 +2618,59 @@ public function inlineCssNotInDebugModeKeepsInvalidOrUnrecognizedSelectorsInMedi
         self::assertContainsCss($css, $subject->render());
     }
 
+    /**
+     * @test
+     */
+    public function getMatchingUninlinableSelectorsReturnsMatchingUninlinableSelector()
+    {
+        $subject = $this->buildDebugSubject('<html><p>foo</p></html>');
+        $subject->inlineCss('p:hover { color: green; }');
+
+        $result = $subject->getMatchingUninlinableSelectors();
+
+        static::assertContains('p:hover', $result);
+    }
+
+    /**
+     * @test
+     */
+    public function getMatchingUninlinableSelectorsReturnsMultipleMatchingUninlinableSelectors()
+    {
+        $subject = $this->buildDebugSubject('<html><p>foo</p></html>');
+        $subject->inlineCss('p:hover { color: green; } p::after { content: "bar"; }');
+
+        $result = $subject->getMatchingUninlinableSelectors();
+
+        static::assertContains('p:hover', $result);
+        static::assertContains('p::after', $result);
+    }
+
+    /**
+     * @test
+     */
+    public function getMatchingUninlinableSelectorsNotReturnsNonMatchingUninlinableSelector()
+    {
+        $subject = $this->buildDebugSubject('<html><p>foo</p></html>');
+        $subject->inlineCss('a:hover { color: red; }');
+
+        $result = $subject->getMatchingUninlinableSelectors();
+
+        static::assertSame([], $result);
+    }
+
+    /**
+     * @test
+     */
+    public function getMatchingUninlinableSelectorsNotReturnsMatchingInlinableSelector()
+    {
+        $subject = $this->buildDebugSubject('<html><p>foo</p></html>');
+        $subject->inlineCss('p { color: red; }');
+
+        $result = $subject->getMatchingUninlinableSelectors();
+
+        static::assertSame([], $result);
+    }
+
     /**
      * @test
      */