Backtracking capable inlines better expressed by interface

src/Components/BacktrackingInline.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Erusev\Parsedown\Components;
+
+use Erusev\Parsedown\Parsing\Excerpt;
+
+interface BacktrackingInline extends Inline
+{
+    /**
+     * Return an integer to declare that the inline should be treated as if it
+     * started from that position in the excerpt given to static::build.
+     * Return null to use the excerpt offset value.
+     * @return int|null
+     * */
+    public function modifyStartPositionTo();
+}

src/Components/Inline.php

@@ -22,14 +22,6 @@ interface Inline extends Component
      * */
     public function width();
 
-    /**
-     * Return an integer to declare that the inline should be treated as if it
-     * started from that position in the excerpt given to static::build.
-     * Return null to use the excerpt offset value.
-     * @return int|null
-     * */
-    public function modifyStartPositionTo();
-
     /**
      * @return Text
      */

src/Components/Inlines/Code.php

@@ -11,7 +11,7 @@ use Erusev\Parsedown\State;
 
 final class Code implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $text;

src/Components/Inlines/DefaultBeginPosition.php

@@ -1,12 +0,0 @@
-<?php
-
-namespace Erusev\Parsedown\Components\Inlines;
-
-trait DefaultBeginPosition
-{
-    /** @return int|null */
-    public function modifyStartPositionTo()
-    {
-        return null;
-    }
-}

src/Components/Inlines/Email.php

@@ -11,7 +11,7 @@ use Erusev\Parsedown\State;
 
 final class Email implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $text;

src/Components/Inlines/Emphasis.php

@@ -13,7 +13,7 @@ use Erusev\Parsedown\State;
 
 final class Emphasis implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $text;

src/Components/Inlines/EscapeSequence.php

@@ -10,7 +10,7 @@ use Erusev\Parsedown\State;
 
 final class EscapeSequence implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     const SPECIALS = '!"#$%&\'()*+,-./:;<=>?@[\]^_`{|}~';
 

src/Components/Inlines/HardBreak.php

@@ -3,13 +3,14 @@
 namespace Erusev\Parsedown\Components\Inlines;
 
 use Erusev\Parsedown\AST\StateRenderable;
+use Erusev\Parsedown\Components\BacktrackingInline;
 use Erusev\Parsedown\Components\Inline;
 use Erusev\Parsedown\Html\Renderables\Element;
 use Erusev\Parsedown\Html\Renderables\Text;
 use Erusev\Parsedown\Parsing\Excerpt;
 use Erusev\Parsedown\State;
 
-final class HardBreak implements Inline
+final class HardBreak implements BacktrackingInline
 {
     use WidthTrait;
 

src/Components/Inlines/Image.php

@@ -16,7 +16,7 @@ use Erusev\Parsedown\State;
 /** @psalm-type _Metadata=array{href: string, title?: string} */
 final class Image implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var Link */
     private $Link;

src/Components/Inlines/Link.php

@@ -18,7 +18,7 @@ use Erusev\Parsedown\State;
 /** @psalm-type _Metadata=array{href: string, title?: string} */
 final class Link implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $label;

src/Components/Inlines/Markup.php

@@ -13,7 +13,7 @@ use Erusev\Parsedown\State;
 
 final class Markup implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     const HTML_ATT_REGEX = '[a-zA-Z_:][\w:.-]*+(?:\s*+=\s*+(?:[^"\'=<>`\s]+|"[^"]*+"|\'[^\']*+\'))?+';
 

src/Components/Inlines/PlainText.php

@@ -10,7 +10,7 @@ use Erusev\Parsedown\State;
 
 final class PlainText implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $text;

src/Components/Inlines/SoftBreak.php

@@ -4,6 +4,7 @@ namespace Erusev\Parsedown\Components\Inlines;
 
 use Erusev\Parsedown\AST\Handler;
 use Erusev\Parsedown\AST\StateRenderable;
+use Erusev\Parsedown\Components\BacktrackingInline;
 use Erusev\Parsedown\Components\Inline;
 use Erusev\Parsedown\Configurables\Breaks;
 use Erusev\Parsedown\Html\Renderables\Container;
@@ -12,7 +13,7 @@ use Erusev\Parsedown\Html\Renderables\Text;
 use Erusev\Parsedown\Parsing\Excerpt;
 use Erusev\Parsedown\State;
 
-final class SoftBreak implements Inline
+final class SoftBreak implements BacktrackingInline
 {
     use WidthTrait;
 

src/Components/Inlines/SpecialCharacter.php

@@ -11,7 +11,7 @@ use Erusev\Parsedown\State;
 
 final class SpecialCharacter implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $charCodeHtml;

src/Components/Inlines/Strikethrough.php

@@ -13,7 +13,7 @@ use Erusev\Parsedown\State;
 
 final class Strikethrough implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $text;

src/Components/Inlines/Url.php

@@ -3,13 +3,14 @@
 namespace Erusev\Parsedown\Components\Inlines;
 
 use Erusev\Parsedown\AST\StateRenderable;
+use Erusev\Parsedown\Components\BacktrackingInline;
 use Erusev\Parsedown\Components\Inline;
 use Erusev\Parsedown\Html\Renderables\Element;
 use Erusev\Parsedown\Html\Renderables\Text;
 use Erusev\Parsedown\Parsing\Excerpt;
 use Erusev\Parsedown\State;
 
-final class Url implements Inline
+final class Url implements BacktrackingInline
 {
     use WidthTrait;
 

src/Components/Inlines/UrlTag.php

@@ -11,7 +11,7 @@ use Erusev\Parsedown\State;
 
 final class UrlTag implements Inline
 {
-    use WidthTrait, DefaultBeginPosition;
+    use WidthTrait;
 
     /** @var string */
     private $url;

src/Parsedown.php

@@ -4,6 +4,7 @@ namespace Erusev\Parsedown;
 
 use Erusev\Parsedown\AST\StateRenderable;
 use Erusev\Parsedown\Components\AcquisitioningBlock;
+use Erusev\Parsedown\Components\BacktrackingInline;
 use Erusev\Parsedown\Components\Block;
 use Erusev\Parsedown\Components\Blocks\Paragraph;
 use Erusev\Parsedown\Components\ContinuableBlock;
@@ -202,7 +203,13 @@ final class Parsedown
                 }
 
                 $markerPosition = $Excerpt->offset();
+
+                /** @var int|null */
+                $startPosition = null;
+
+                if ($Inline instanceof BacktrackingInline) {
                     $startPosition = $Inline->modifyStartPositionTo();
+                }
 
                 if (! isset($startPosition)) {
                     $startPosition = $markerPosition;