Added a configuration option to abbr and

handling for empty abbreviations.

- Configuration option `use_last_abbr` allows using
the first instance of a term rather than the last.
This is useful for sites that auto-append a glossary
to pages.
- If an abbreviation does not have a definition it
will skip the term instead of writing abbr tags with
an empty title.

docs/changelog.md

@@ -25,7 +25,19 @@ A call to `Markdown.reset()` now clears all previously defined abbreviations.
 
 Abbreviations are now sorted by length before executing `AbbrTreeprocessor`
 to ensure that multi-word abbreviations are implemented even if an abbreviation
-exists for one of those component words.
+exists for one of those component words. (#1465)
+
+Added an optional `use_last_abbr` configuration option to the abbreviations
+extension. Default (`True`) maintains the existing behavior. `False` causes
+the extension to only use the first instance of an abbreviation, rather than
+the last.
+
+Empty abbreviations are now skipped by `AbbrTreeprocessor`. This avoids applying
+abbr tags to text without a title value. This also allows disabling an
+abbreviation, which may be useful for documents that uses two terms with
+identical abbreviations.
+
+
 
 ### Fixed
 

docs/extensions/abbreviations.md

@@ -1,5 +1,10 @@
 title: Abbreviations Extension
 
+ABBR
+
+*[ABBR]: Abbreviation
+*[ABBR]: Override Ignored
+
 Abbreviations
 =============
 

markdown/extensions/abbr.py

@@ -23,6 +23,7 @@
 from __future__ import annotations
 
 from . import Extension
+from ..util import parseBoolValue
 from ..blockprocessors import BlockProcessor
 from ..inlinepatterns import InlineProcessor
 from ..treeprocessors import Treeprocessor
@@ -41,6 +42,14 @@ class AbbrExtension(Extension):
 
     def __init__(self, **kwargs):
         """ Initiate Extension and set up configs. """
+        self.config = {
+            'use_last_abbr': [
+                True,
+                'True to use the last instance of an abbreviation, rather than the first instance.'
+                'Default: `True`.'
+            ],
+        }
+        """ Default configuration options. """
         super().__init__(**kwargs)
         self.abbrs = {}
 
@@ -52,7 +61,7 @@ def extendMarkdown(self, md):
         """ Insert `AbbrTreeprocessor` and `AbbrBlockprocessor`. """
         md.registerExtension(self)
         md.treeprocessors.register(AbbrTreeprocessor(md, self.abbrs), 'abbr', 7)
-        md.parser.blockprocessors.register(AbbrBlockprocessor(md.parser, self.abbrs), 'abbr', 16)
+        md.parser.blockprocessors.register(AbbrBlockprocessor(md.parser, self.abbrs, self.getConfigs()), 'abbr', 16)
 
 
 class AbbrTreeprocessor(Treeprocessor):
@@ -69,11 +78,12 @@ def iter_element(self, el: etree.Element, parent: etree.Element | None = None) -
             self.iter_element(child, el)
         if text := el.text:
             for m in reversed(list(self.RE.finditer(text))):
-                abbr = etree.Element('abbr', {'title': self.abbrs[m.group(0)]})
-                abbr.text = AtomicString(m.group(0))
-                abbr.tail = text[m.end():]
-                el.insert(0, abbr)
-                text = text[:m.start()]
+                if self.abbrs[m.group(0)]:
+                    abbr = etree.Element('abbr', {'title': self.abbrs[m.group(0)]})
+                    abbr.text = AtomicString(m.group(0))
+                    abbr.tail = text[m.end():]
+                    el.insert(0, abbr)
+                    text = text[:m.start()]
             el.text = text
         if parent and el.tail:
             tail = el.tail
@@ -104,8 +114,9 @@ class AbbrBlockprocessor(BlockProcessor):
 
     RE = re.compile(r'^[*]\[(?P<abbr>[^\\]*?)\][ ]?:[ ]*\n?[ ]*(?P<title>.*)$', re.MULTILINE)
 
-    def __init__(self, parser: BlockParser, abbrs: dict):
+    def __init__(self, parser: BlockParser, abbrs: dict, config: dict[str, Any]):
         self.abbrs: dict = abbrs
+        self.use_last_abbr: bool = parseBoolValue(config["use_last_abbr"])
         super().__init__(parser)
 
     def test(self, parent: etree.Element, block: str) -> bool:
@@ -122,7 +133,8 @@ def run(self, parent: etree.Element, blocks: list[str]) -> bool:
         if m:
             abbr = m.group('abbr').strip()
             title = m.group('title').strip()
-            self.abbrs[abbr] = title
+            if self.use_last_abbr or abbr not in self.abbrs:
+                self.abbrs[abbr] = title
             if block[m.end():].strip():
                 # Add any content after match back to blocks as separate block
                 blocks.insert(0, block[m.end():].lstrip('\n'))

tests/test_syntax/extensions/test_abbr.py

@@ -133,7 +133,26 @@ def test_abbr_override(self):
                 """
                 <p><abbr title="The override">ABBR</abbr></p>
                 """
-            )
+            ),
+            extensions=[AbbrExtension(use_last_abbr=True)]
+        )
+
+    def test_abbr_override_Ignored(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                ABBR
+
+                *[ABBR]: Abbreviation
+                *[ABBR]: Override Ignored
+                """
+            ),
+            self.dedent(
+                """
+                <p><abbr title="Abbreviation">ABBR</abbr></p>
+                """
+            ),
+            extensions=[AbbrExtension(use_last_abbr=False)]
         )
 
     def test_abbr_nested(self):
@@ -401,6 +420,26 @@ def test_abbr_superset_vs_subset(self):
             )
         )
 
+    def test_abbr_empty(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                """
+                *[abbr]: Abbreviation Definition
+
+                abbr
+
+                *[abbr]:
+
+                Testing document text.
+                """
+            ),
+            self.dedent(
+                """
+                <p>abbr</p>\n<p>Testing document text.</p>
+                """
+            )
+        )
+
     def test_abbr_reset(self):
         ext = AbbrExtension()
         md = Markdown(extensions=[ext])