Explicitly omit carot and backslash from abbr

Fixes #1444.

docs/changelog.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Include `scripts/*.py` in the generated source tarballs (#1430).
 * Ensure lines after heading in loose list are properly detabbed (#1443).
 * Give smarty tree processor higher priority than toc (#1440).
+* Explicitly omit carrot (`^`) and backslash (`\`) from abbreviations (#1444).
 
 ## [3.5.2] -- 2024-01-10
 

docs/extensions/abbreviations.md

@@ -36,6 +36,14 @@ will be rendered as:
 is maintained by the <abbr title="World Wide Web Consortium">W3C</abbr>.</p>
 ```
 
+The following three characters are not permitted in an abbreviation. Any
+abbreviation definitions which include one will not be recognized as an
+abbreviation definition.
+
+1. carrot (`^`)
+2. backslash (`\`)
+3. left square bracket (`]`)
+
 Usage
 -----
 

markdown/extensions/abbr.py

@@ -41,7 +41,7 @@ def extendMarkdown(self, md):
 class AbbrPreprocessor(BlockProcessor):
     """ Abbreviation Preprocessor - parse text for abbr references. """
 
-    RE = re.compile(r'^[*]\[(?P<abbr>[^\]]*)\][ ]?:[ ]*\n?[ ]*(?P<title>.*)$', re.MULTILINE)
+    RE = re.compile(r'^[*]\[(?P<abbr>[^\]\^\\]*)\][ ]?:[ ]*\n?[ ]*(?P<title>.*)$', re.MULTILINE)
 
     def test(self, parent: etree.Element, block: str) -> bool:
         return True
@@ -73,18 +73,15 @@ def run(self, parent: etree.Element, blocks: list[str]) -> bool:
 
     def _generate_pattern(self, text: str) -> str:
         """
-        Given a string, returns an regex pattern to match that string.
+        Given a string, returns a regex pattern to match that string.
 
-        'HTML' -> r'(?P<abbr>[H][T][M][L])'
+        'HTML' -> r'(?P<abbr>\b[H][T][M][L]\b)'
 
-        Note: we force each char as a literal match (in brackets) as we don't
-        know what they will be beforehand.
+        Note: we force each char as a literal match via a character set (in brackets)
+        as we don't know what they will be beforehand.
 
         """
-        chars = list(text)
-        for i in range(len(chars)):
-            chars[i] = r'[%s]' % chars[i]
-        return r'(?P<abbr>\b%s\b)' % (r''.join(chars))
+        return f"(?P<abbr>\\b{ ''.join(f'[{ c }]' for c in text) }\\b)"
 
 
 class AbbrInlineProcessor(InlineProcessor):

tests/test_extensions.py

@@ -85,35 +85,6 @@ def testConfigAsKwargsOnInit(self):
         self.assertEqual(ext.getConfigs(), {'foo': 'baz', 'bar': 'blah'})
 
 
-class TestAbbr(unittest.TestCase):
-    """ Test abbr extension. """
-
-    def setUp(self):
-        self.md = markdown.Markdown(extensions=['abbr'])
-
-    def testSimpleAbbr(self):
-        """ Test Abbreviations. """
-        text = 'Some text with an ABBR and a REF. Ignore REFERENCE and ref.' + \
-               '\n\n*[ABBR]: Abbreviation\n' + \
-               '*[REF]: Abbreviation Reference'
-        self.assertEqual(
-            self.md.convert(text),
-            '<p>Some text with an <abbr title="Abbreviation">ABBR</abbr> '
-            'and a <abbr title="Abbreviation Reference">REF</abbr>. Ignore '
-            'REFERENCE and ref.</p>'
-        )
-
-    def testNestedAbbr(self):
-        """ Test Nested Abbreviations. """
-        text = '[ABBR](/foo) and _ABBR_\n\n' + \
-               '*[ABBR]: Abbreviation'
-        self.assertEqual(
-            self.md.convert(text),
-            '<p><a href="/foo"><abbr title="Abbreviation">ABBR</abbr></a> '
-            'and <em><abbr title="Abbreviation">ABBR</abbr></em></p>'
-        )
-
-
 class TestMetaData(unittest.TestCase):
     """ Test `MetaData` extension. """
 

tests/test_syntax/extensions/test_abbr.py

@@ -95,6 +95,25 @@ def test_abbr_override(self):
             )
         )
 
+    def test_abbr_nested(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                [ABBR](/foo)
+
+                _ABBR_
+
+                *[ABBR]: Abbreviation
+                """
+            ),
+            self.dedent(
+                """
+                <p><a href="/foo"><abbr title="Abbreviation">ABBR</abbr></a></p>
+                <p><em><abbr title="Abbreviation">ABBR</abbr></em></p>
+                """
+            )
+        )
+
     def test_abbr_no_blank_Lines(self):
         self.assertMarkdownRenders(
             self.dedent(
@@ -240,3 +259,45 @@ def test_abbr_single_quoted(self):
                 """
             )
         )
+
+    def test_abbr_ignore_special_chars(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                r"""
+                [^] [\\] [\]] []]
+
+                *[^]: Not an abbreviation
+
+                *[\\]: Not an abbreviation
+
+                *[\]]: Not an abbreviation
+
+                *[]]: Not an abbreviation
+                """
+            ),
+            self.dedent(
+                r"""
+                <p>[^] [\] []] []]</p>
+                <p>*[^]: Not an abbreviation</p>
+                <p>*[\]: Not an abbreviation</p>
+                <p>*[]]: Not an abbreviation</p>
+                <p>*[]]: Not an abbreviation</p>
+                """
+            )
+        )
+
+    def test_abbr_hyphen(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                ABBR-abbr
+
+                *[ABBR-abbr]: Abbreviation
+                """
+            ),
+            self.dedent(
+                """
+                <p><abbr title="Abbreviation">ABBR-abbr</abbr></p>
+                """
+            )
+        )