From 91b4fcd55f5f930e10e98dec93f30651614365ca Mon Sep 17 00:00:00 2001
From: David Anson <david@dlaa.me>
Date: Fri, 26 Jul 2019 23:03:56 -0700
Subject: [PATCH] Update MD026/no-trailing-punctuation to handle empty
 punctuation paramater, escape for RegExp (fixes #205).

---
 doc/Rules.md                                      | 15 ++++++++-------
 lib/md026.js                                      | 14 +++++++++-----
 test/heading_trailing_punctuation_customized.json |  2 +-
 test/heading_trailing_punctuation_customized.md   |  2 ++
 test/heading_trailing_punctuation_empty.json      |  6 ++++++
 test/heading_trailing_punctuation_empty.md        | 13 +++++++++++++
 6 files changed, 39 insertions(+), 13 deletions(-)
 create mode 100644 test/heading_trailing_punctuation_empty.json
 create mode 100644 test/heading_trailing_punctuation_empty.md

diff --git a/doc/Rules.md b/doc/Rules.md
index 01fd7452..4a86c1a7 100644
--- a/doc/Rules.md
+++ b/doc/Rules.md
@@ -792,23 +792,24 @@ Aliases: no-trailing-punctuation
 
 Parameters: punctuation (string; default ".,;:!?。，；：！？")
 
-This rule is triggered on any heading that has a normal or full-width punctuation
-character as the last character in the line:
+This rule is triggered on any heading that has one of the specified normal or
+full-width punctuation characters as the last character in the line:
 
 ```markdown
 # This is a heading.
 ```
 
-To fix this, remove any trailing punctuation:
+To fix this, remove the trailing punctuation:
 
 ```markdown
 # This is a heading
 ```
 
-Note: The punctuation parameter can be used to specify what characters class
-as punctuation at the end of the heading. For example, you can set it to
-`".,;:!"` to allow headings with question marks in them, such as might be used
-in an FAQ.
+Note: The `punctuation` parameter can be used to specify what characters count
+as punctuation at the end of a heading. For example, you can change it to
+`".,;:!"` to allow headings that end with a question mark, such as in an FAQ.
+Setting the `punctuation` parameter to `""` allows all characters - and is
+equivalent to disabling the rule.
 
 <a name="md027"></a>
 
diff --git a/lib/md026.js b/lib/md026.js
index cc7a93ee..88881255 100644
--- a/lib/md026.js
+++ b/lib/md026.js
@@ -2,17 +2,21 @@
 
 "use strict";
 
-const { addError, allPunctuation, forEachHeading, rangeFromRegExp } =
-  require("../helpers");
+const { addError, allPunctuation, escapeForRegExp, forEachHeading,
+  rangeFromRegExp } = require("../helpers");
 
 module.exports = {
   "names": [ "MD026", "no-trailing-punctuation" ],
   "description": "Trailing punctuation in heading",
   "tags": [ "headings", "headers" ],
   "function": function MD026(params, onError) {
-    const punctuation = params.config.punctuation || allPunctuation;
-    const trailingPunctuationRe = new RegExp("[" + punctuation + "]$");
-    forEachHeading(params, function forHeading(heading, content) {
+    let punctuation = params.config.punctuation;
+    if (punctuation === undefined) {
+      punctuation = allPunctuation;
+    }
+    const trailingPunctuationRe =
+      new RegExp("[" + escapeForRegExp(punctuation) + "]$");
+    forEachHeading(params, (heading, content) => {
       const match = trailingPunctuationRe.exec(content);
       if (match) {
         addError(onError, heading.lineNumber,
diff --git a/test/heading_trailing_punctuation_customized.json b/test/heading_trailing_punctuation_customized.json
index df827f91..91ca4506 100644
--- a/test/heading_trailing_punctuation_customized.json
+++ b/test/heading_trailing_punctuation_customized.json
@@ -1,6 +1,6 @@
 {
   "default": true,
   "MD026": {
-    "punctuation": ".,;:!"
+    "punctuation": ".,;:!]"
   }
 }
diff --git a/test/heading_trailing_punctuation_customized.md b/test/heading_trailing_punctuation_customized.md
index e44f5482..69679422 100644
--- a/test/heading_trailing_punctuation_customized.md
+++ b/test/heading_trailing_punctuation_customized.md
@@ -10,5 +10,7 @@
 
 ## Heading 6?
 
+## Heading 7 {MD026}]
+
 The rule has been customized to allow question marks while disallowing
 everything else.
diff --git a/test/heading_trailing_punctuation_empty.json b/test/heading_trailing_punctuation_empty.json
new file mode 100644
index 00000000..84f341a2
--- /dev/null
+++ b/test/heading_trailing_punctuation_empty.json
@@ -0,0 +1,6 @@
+{
+  "default": true,
+  "MD026": {
+    "punctuation": ""
+  }
+}
diff --git a/test/heading_trailing_punctuation_empty.md b/test/heading_trailing_punctuation_empty.md
new file mode 100644
index 00000000..ab7d7090
--- /dev/null
+++ b/test/heading_trailing_punctuation_empty.md
@@ -0,0 +1,13 @@
+# Heading Trailing Punctuation
+
+## Heading .
+
+## Heading ,
+
+## Heading ;
+
+## Heading :
+
+## Heading !
+
+## Heading ?