feat(disableForced4SpacesIndentedSublists): option that disables the requirement of indenting nested sublists by 4 spaces

README.md

@@ -260,6 +260,9 @@ var defaultOptions = showdown.getDefaultOptions();
  
  * **smartIndentationFix**: (boolean) [default false] Tries to smartly fix indentation problems related to es6 template strings in the midst of indented code.
 
+ * **disableForced4SpacesIndentedSublists**: (boolean) [default false] Disables the requirement of indenting sublists by 4 spaces for them to be nested, 
+ effectively reverting to the old behavior where 2 or 3 spaces were enough. (since v1.5.0)
+ 
 ## CLI Tool
 
 Showdown also comes bundled with a Command Line Interface tool. You can check the [CLI wiki page][cli-wiki] for more info

src/options.js

@@ -75,6 +75,11 @@ function getDefaultOpts(simple) {
       defaultValue: false,
       description: 'Tries to smartly fix indentation in es6 strings',
       type: 'boolean'
+    },
+    disableForced4SpacesIndentedSublists: {
+      defaultValue: false,
+      description: 'Disables the requirement of indenting nested sublists by 4 spaces',
+      type: 'boolean'
     }
   };
   if (simple === false) {

src/showdown.js

@@ -17,7 +17,8 @@ var showdown = {},
         tables:                               true,
         tablesHeaderId:                       true,
         ghCodeBlocks:                         true,
-        tasklists:                 true
+        tasklists:                            true,
+        disableForced4SpacesIndentedSublists: true
       },
       vanilla: getDefaultOpts(true)
     };

src/subParsers/lists.js

@@ -44,6 +44,13 @@ showdown.subParser('lists', function (text, options, globals) {
     var rgx = /(\n)?(^ {0,3})([*+-]|\d+[.])[ \t]+((\[(x|X| )?])?[ \t]*[^\r]+?(\n{1,2}))(?=\n*(~0| {0,3}([*+-]|\d+[.])[ \t]+))/gm,
         isParagraphed = (/\n[ \t]*\n(?!~0)/.test(listStr));
 
+    // Since version 1.5, nesting sublists requires 4 spaces (or 1 tab) indentation,
+    // which is a syntax breaking change
+    // activating this option reverts to old behavior
+    if (options.disableForced4SpacesIndentedSublists) {
+      rgx = /(\n)?(^ {0,3})([*+-]|\d+[.])[ \t]+((\[(x|X| )?])?[ \t]*[^\r]+?(\n{1,2}))(?=\n*(~0|\2([*+-]|\d+[.])[ \t]+))/gm;
+    }
+
     listStr = listStr.replace(rgx, function (wholeMatch, m1, m2, m3, m4, taskbtn, checked) {
       checked = (checked && checked.trim() !== '');
 
@@ -105,8 +112,8 @@ showdown.subParser('lists', function (text, options, globals) {
   function parseConsecutiveLists(list, listType, trimTrailing) {
     // check if we caught 2 or more consecutive lists by mistake
     // we use the counterRgx, meaning if listType is UL we look for OL and vice versa
-    var olRgx = /^ {0,3}\d+\.[ \t]/gm,
-        ulRgx = /^ {0,3}[*+-][ \t]/gm,
+    var olRgx = (options.disableForced4SpacesIndentedSublists) ? /^ ?\d+\.[ \t]/gm : /^ {0,3}\d+\.[ \t]/gm,
+        ulRgx = (options.disableForced4SpacesIndentedSublists) ? /^ ?[*+-][ \t]/gm : /^ {0,3}[*+-][ \t]/gm,
         counterRxg = (listType === 'ul') ? olRgx : ulRgx,
         result = '';
 

test/features/disableForced4SpacesIndentedSublists.html

@@ -0,0 +1,13 @@
+<ul>
+  <li>foo
+
+    <ul>
+      <li>bar</li></ul></li>
+</ul>
+<p>...</p>
+<ul>
+  <li>baz
+
+    <ol>
+      <li>bazinga</li></ol></li>
+</ul>

test/features/disableForced4SpacesIndentedSublists.md

@@ -0,0 +1,7 @@
+* foo
+  * bar
+
+...
+
+* baz
+  1. bazinga

test/node/testsuite.features.js

@@ -33,6 +33,8 @@ describe('makeHtml() features testsuite', function () {
       converter = new showdown.Converter({smartIndentationFix: true});
     } else if (testsuite[i].name === '#284.simplifiedAutoLink-does-not-match-GFM-style') {
       converter = new showdown.Converter({simplifiedAutoLink: true});
+    } else if (testsuite[i].name === 'disableForced4SpacesIndentedSublists') {
+      converter = new showdown.Converter({disableForced4SpacesIndentedSublists: true});
     } else {
       converter = new showdown.Converter();
     }