From 66bf8e6ace796337ea0c4eec6a2a783db89578f5 Mon Sep 17 00:00:00 2001
From: Krille Fear <christian-pauly@posteo.de>
Date: Tue, 16 Nov 2021 08:18:07 +0100
Subject: [PATCH] fix: HtmlToText crashes with an empty code block

---
 lib/src/utils/html_to_text.dart |  24 ++---
 test/html_to_text_test.dart     | 149 ++++++++++++++++----------------
 2 files changed, 89 insertions(+), 84 deletions(-)

diff --git a/lib/src/utils/html_to_text.dart b/lib/src/utils/html_to_text.dart
index 2abbf0a4..aa4d0bf2 100644
--- a/lib/src/utils/html_to_text.dart
+++ b/lib/src/utils/html_to_text.dart
@@ -50,11 +50,13 @@ class HtmlToText {
             .firstMatch(text);
     if (match == null) {
       text = HtmlUnescape().convert(text);
-      if (text[0] != '\n') {
-        text = '\n$text';
-      }
-      if (text[text.length - 1] != '\n') {
-        text += '\n';
+      if (text.isNotEmpty) {
+        if (text[0] != '\n') {
+          text = '\n$text';
+        }
+        if (text[text.length - 1] != '\n') {
+          text += '\n';
+        }
       }
       return text;
     }
@@ -64,11 +66,13 @@ class HtmlToText {
     text = text.replaceAll(
         RegExp(r'</code>$', multiLine: false, caseSensitive: false), '');
     text = HtmlUnescape().convert(text);
-    if (text[0] != '\n') {
-      text = '\n$text';
-    }
-    if (text[text.length - 1] != '\n') {
-      text += '\n';
+    if (text.isNotEmpty) {
+      if (text[0] != '\n') {
+        text = '\n$text';
+      }
+      if (text[text.length - 1] != '\n') {
+        text += '\n';
+      }
     }
     final language =
         RegExp(r'language-(\w+)', multiLine: false, caseSensitive: false)
diff --git a/test/html_to_text_test.dart b/test/html_to_text_test.dart
index fc29a6a3..9dde56e7 100644
--- a/test/html_to_text_test.dart
+++ b/test/html_to_text_test.dart
@@ -21,80 +21,81 @@ import 'package:test/test.dart';
 
 void main() {
   group('htmlToText', () {
-    test('stuff', () async {
-      final testMap = <String, String>{
-        '': '',
-        'hello world\nthis is a test': 'hello world\nthis is a test',
-        '<em>That\'s</em> not a test, <strong>this</strong> is a test':
-            '*That\'s* not a test, **this** is a test',
-        'Visit <del><a href="http://example.com">our website</a></del> (outdated)':
-            'Visit ~~🔗our website~~ (outdated)',
-        '(cw spiders) <span data-mx-spoiler>spiders are pretty cool</span>':
-            '(cw spiders) ███████████████████████',
-        '<span data-mx-spoiler="cw spiders">spiders are pretty cool</span>':
-            '(cw spiders) ███████████████████████',
-        '<img src="test.gif" alt="a test case" />': 'a test case',
-        'List of cute animals:\n<ul>\n<li>Kittens</li>\n<li>Puppies</li>\n<li>Snakes<br/>(I think they\'re cute!)</li>\n</ul>\n(This list is incomplete, you can help by adding to it!)':
-            'List of cute animals:\n● Kittens\n● Puppies\n● Snakes\n  (I think they\'re cute!)\n(This list is incomplete, you can help by adding to it!)',
-        '<em>fox</em>': '*fox*',
-        '<i>fox</i>': '*fox*',
-        '<strong>fox</i>': '**fox**',
-        '<b>fox</b>': '**fox**',
-        '<u>fox</u>': '__fox__',
-        '<ins>fox</ins>': '__fox__',
-        '<del>fox</del>': '~~fox~~',
-        '<strike>fox</strike>': '~~fox~~',
-        '<s>fox</s>': '~~fox~~',
-        '<code>&gt;fox</code>': '`>fox`',
-        '<pre>meep</pre>': '```\nmeep\n```',
-        '<pre>meep\n</pre>': '```\nmeep\n```',
-        '<pre><code class="language-floof">meep</code></pre>':
-            '```floof\nmeep\n```',
-        'before<pre>code</pre>after': 'before\n```\ncode\n```\nafter',
-        '<p>before</p><pre>code</pre><p>after</p>':
-            'before\n```\ncode\n```\nafter',
-        '<p>fox</p>': 'fox',
-        '<p>fox</p><p>floof</p>': 'fox\n\nfloof',
-        '<a href="https://example.org">website</a>': '🔗website',
-        '<a href="https://matrix.to/#/@user:example.org">fox</a>': 'fox',
-        '<a href="matrix:u/user:example.org">fox</a>': 'fox',
-        '<img alt=":wave:" src="mxc://fox">': ':wave:',
-        'fox<br>floof': 'fox\nfloof',
-        '<blockquote>fox</blockquote>floof': '> fox\nfloof',
-        '<blockquote><p>fox</p></blockquote>floof': '> fox\nfloof',
-        '<blockquote><p>fox</p></blockquote><p>floof</p>': '> fox\nfloof',
-        'a<blockquote>fox</blockquote>floof': 'a\n> fox\nfloof',
-        '<blockquote><blockquote>fox</blockquote>floof</blockquote>fluff':
-            '> > fox\n> floof\nfluff',
-        '<ul><li>hey<ul><li>a</li><li>b</li></ul></li><li>foxies</li></ul>':
-            '● hey\n      ○ a\n      ○ b\n● foxies',
-        '<ol><li>a</li><li>b</li></ol>': '1. a\n2. b',
-        '<ol start="42"><li>a</li><li>b</li></ol>': '42. a\n43. b',
-        '<ol><li>a<ol><li>aa</li><li>bb</li></ol></li><li>b</li></ol>':
-            '1. a\n      1. aa\n      2. bb\n2. b',
-        '<ol><li>a<ul><li>aa</li><li>bb</li></ul></li><li>b</li></ol>':
-            '1. a\n      ○ aa\n      ○ bb\n2. b',
-        '<ul><li>a<ol><li>aa</li><li>bb</li></ol></li><li>b</li></ul>':
-            '● a\n      1. aa\n      2. bb\n● b',
-        '<mx-reply>bunny</mx-reply>fox': 'fox',
-        'fox<hr>floof': 'fox\n----------\nfloof',
-        '<p>fox</p><hr><p>floof</p>': 'fox\n----------\nfloof',
-        '<h1>fox</h1>floof': '# fox\nfloof',
-        '<h1>fox</h1><p>floof</p>': '# fox\nfloof',
-        'floof<h1>fox</h1>': 'floof\n# fox',
-        '<p>floof</p><h1>fox</h1>': 'floof\n# fox',
-        '<h2>fox</h2>': '## fox',
-        '<h3>fox</h3>': '### fox',
-        '<h4>fox</h4>': '#### fox',
-        '<h5>fox</h5>': '##### fox',
-        '<h6>fox</h6>': '###### fox',
-        '<span>fox</span>': 'fox',
-        '<p>fox</p>\n<p>floof</p>': 'fox\n\nfloof',
-        '<mx-reply>beep</mx-reply><p>fox</p>\n<p>floof</p>': 'fox\n\nfloof',
-      };
-      for (final entry in testMap.entries) {
+    final testMap = <String, String>{
+      '': '',
+      'hello world\nthis is a test': 'hello world\nthis is a test',
+      '<em>That\'s</em> not a test, <strong>this</strong> is a test':
+          '*That\'s* not a test, **this** is a test',
+      'Visit <del><a href="http://example.com">our website</a></del> (outdated)':
+          'Visit ~~🔗our website~~ (outdated)',
+      '(cw spiders) <span data-mx-spoiler>spiders are pretty cool</span>':
+          '(cw spiders) ███████████████████████',
+      '<span data-mx-spoiler="cw spiders">spiders are pretty cool</span>':
+          '(cw spiders) ███████████████████████',
+      '<img src="test.gif" alt="a test case" />': 'a test case',
+      'List of cute animals:\n<ul>\n<li>Kittens</li>\n<li>Puppies</li>\n<li>Snakes<br/>(I think they\'re cute!)</li>\n</ul>\n(This list is incomplete, you can help by adding to it!)':
+          'List of cute animals:\n● Kittens\n● Puppies\n● Snakes\n  (I think they\'re cute!)\n(This list is incomplete, you can help by adding to it!)',
+      '<em>fox</em>': '*fox*',
+      '<i>fox</i>': '*fox*',
+      '<strong>fox</i>': '**fox**',
+      '<b>fox</b>': '**fox**',
+      '<u>fox</u>': '__fox__',
+      '<ins>fox</ins>': '__fox__',
+      '<del>fox</del>': '~~fox~~',
+      '<strike>fox</strike>': '~~fox~~',
+      '<s>fox</s>': '~~fox~~',
+      '<code>&gt;fox</code>': '`>fox`',
+      '<pre>meep</pre>': '```\nmeep\n```',
+      '<pre>meep\n</pre>': '```\nmeep\n```',
+      '<pre><code class="language-floof">meep</code></pre>':
+          '```floof\nmeep\n```',
+      'before<pre>code</pre>after': 'before\n```\ncode\n```\nafter',
+      '<p>before</p><pre>code</pre><p>after</p>':
+          'before\n```\ncode\n```\nafter',
+      '<p>fox</p>': 'fox',
+      '<p>fox</p><p>floof</p>': 'fox\n\nfloof',
+      '<a href="https://example.org">website</a>': '🔗website',
+      '<a href="https://matrix.to/#/@user:example.org">fox</a>': 'fox',
+      '<a href="matrix:u/user:example.org">fox</a>': 'fox',
+      '<img alt=":wave:" src="mxc://fox">': ':wave:',
+      'fox<br>floof': 'fox\nfloof',
+      '<blockquote>fox</blockquote>floof': '> fox\nfloof',
+      '<blockquote><p>fox</p></blockquote>floof': '> fox\nfloof',
+      '<blockquote><p>fox</p></blockquote><p>floof</p>': '> fox\nfloof',
+      'a<blockquote>fox</blockquote>floof': 'a\n> fox\nfloof',
+      '<blockquote><blockquote>fox</blockquote>floof</blockquote>fluff':
+          '> > fox\n> floof\nfluff',
+      '<ul><li>hey<ul><li>a</li><li>b</li></ul></li><li>foxies</li></ul>':
+          '● hey\n      ○ a\n      ○ b\n● foxies',
+      '<ol><li>a</li><li>b</li></ol>': '1. a\n2. b',
+      '<ol start="42"><li>a</li><li>b</li></ol>': '42. a\n43. b',
+      '<ol><li>a<ol><li>aa</li><li>bb</li></ol></li><li>b</li></ol>':
+          '1. a\n      1. aa\n      2. bb\n2. b',
+      '<ol><li>a<ul><li>aa</li><li>bb</li></ul></li><li>b</li></ol>':
+          '1. a\n      ○ aa\n      ○ bb\n2. b',
+      '<ul><li>a<ol><li>aa</li><li>bb</li></ol></li><li>b</li></ul>':
+          '● a\n      1. aa\n      2. bb\n● b',
+      '<mx-reply>bunny</mx-reply>fox': 'fox',
+      'fox<hr>floof': 'fox\n----------\nfloof',
+      '<p>fox</p><hr><p>floof</p>': 'fox\n----------\nfloof',
+      '<h1>fox</h1>floof': '# fox\nfloof',
+      '<h1>fox</h1><p>floof</p>': '# fox\nfloof',
+      'floof<h1>fox</h1>': 'floof\n# fox',
+      '<p>floof</p><h1>fox</h1>': 'floof\n# fox',
+      '<h2>fox</h2>': '## fox',
+      '<h3>fox</h3>': '### fox',
+      '<h4>fox</h4>': '#### fox',
+      '<h5>fox</h5>': '##### fox',
+      '<h6>fox</h6>': '###### fox',
+      '<span>fox</span>': 'fox',
+      '<p>fox</p>\n<p>floof</p>': 'fox\n\nfloof',
+      '<mx-reply>beep</mx-reply><p>fox</p>\n<p>floof</p>': 'fox\n\nfloof',
+      '<pre><code></code></pre>': '``````',
+    };
+    for (final entry in testMap.entries) {
+      test(entry.key, () async {
         expect(HtmlToText.convert(entry.key), entry.value);
-      }
-    });
+      });
+    }
   });
 }