Require Inlines to provide a best plaintext rendering

This allows markdown to be parsed "inside" the alt
attribute of an image, and then the best plaintext
can be used as the rest.
This improves CommonMark compliance.

src/Components/Inline.php

@@ -3,6 +3,7 @@
 namespace Erusev\Parsedown\Components;
 
 use Erusev\Parsedown\Component;
+use Erusev\Parsedown\Html\Renderables\Text;
 use Erusev\Parsedown\Parsing\Excerpt;
 use Erusev\Parsedown\State;
 
@@ -28,4 +29,9 @@ interface Inline extends Component
      * @return int|null
      * */
     public function modifyStartPositionTo();
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext();
 }

src/Components/Inlines/Code.php

@@ -58,4 +58,12 @@ final class Code implements Inline
     {
         return new Element('code', [], [new Text($this->text)]);
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->text);
+    }
 }

src/Components/Inlines/Email.php

@@ -64,4 +64,12 @@ final class Email implements Inline
     {
         return new Element('a', ['href' => $this->url], [new Text($this->text)]);
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->text);
+    }
 }

src/Components/Inlines/Emphasis.php

@@ -85,4 +85,12 @@ final class Emphasis implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->text);
+    }
 }

src/Components/Inlines/EscapeSequence.php

@@ -5,6 +5,7 @@ namespace Erusev\Parsedown\Components\Inlines;
 use Erusev\Parsedown\AST\StateRenderable;
 use Erusev\Parsedown\Components\Inline;
 use Erusev\Parsedown\Html\Renderables\RawHtml;
+use Erusev\Parsedown\Html\Renderables\Text;
 use Erusev\Parsedown\Parsedown;
 use Erusev\Parsedown\Parsing\Excerpt;
 use Erusev\Parsedown\State;
@@ -48,4 +49,12 @@ final class EscapeSequence implements Inline
     {
         return new RawHtml($this->html);
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->html);
+    }
 }

src/Components/Inlines/Image.php

@@ -61,7 +61,20 @@ final class Image implements Inline
             function (State $State) use ($Parsedown) {
                 $attributes = [
                     'src' => $this->Link->url(),
-                    'alt' => $this->Link->label(),
+                    'alt' => \array_reduce(
+                        $Parsedown->inlines($this->Link->label()),
+                        /**
+                         * @param string $text
+                         * @return string
+                         */
+                        function ($text, Inline $Inline) {
+                            return (
+                                $text
+                                . $Inline->bestPlaintext()->getStringBacking()
+                            );
+                        },
+                        ''
+                    ),
                 ];
 
                 $title = $this->Link->title();
@@ -78,4 +91,12 @@ final class Image implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->Link->label());
+    }
 }

src/Components/Inlines/Link.php

@@ -134,4 +134,12 @@ final class Link implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->label);
+    }
 }

src/Components/Inlines/Markup.php

@@ -74,4 +74,12 @@ final class Markup implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->html);
+    }
 }

src/Components/Inlines/PlainText.php

@@ -72,4 +72,12 @@ final class PlainText implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->text);
+    }
 }

src/Components/Inlines/SpecialCharacter.php

@@ -51,4 +51,12 @@ final class SpecialCharacter implements Inline
             '&' . (new Text($this->charCodeHtml))->getHtml() . ';'
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text('&'.$this->charCodeHtml.';');
+    }
 }

src/Components/Inlines/Strikethrough.php

@@ -64,4 +64,12 @@ final class Strikethrough implements Inline
             }
         );
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->text);
+    }
 }

src/Components/Inlines/Url.php

@@ -71,4 +71,12 @@ final class Url implements Inline
     {
         return new Element('a', ['href' => $this->url], [new Text($this->url)]);
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->url);
+    }
 }

src/Components/Inlines/UrlTag.php

@@ -48,4 +48,12 @@ final class UrlTag implements Inline
     {
         return new Element('a', ['href' => $this->url], [new Text($this->url)]);
     }
+
+    /**
+     * @return Text
+     */
+    public function bestPlaintext()
+    {
+        return new Text($this->url);
+    }
 }