1 files changed, 49 insertions, 0 deletions
diff --git a/markdown/extensions/legacy_attrs.py b/markdown/extensions/legacy_attrs.py
new file mode 100644
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+++ b/markdown/extensions/legacy_attrs.py
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+"""
+Legacy Attributes Extension
+===========================
+
+An extension to Python Markdown which implements legacy attributes.
+
+Prior to Python-Markdown version 3.0, the Markdown class had an `enable_attributes`
+keyword which was on by default and provided for attributes to be defined for elements
+using the format `{@key=value}`. This extension is provided as a replacement for
+backward compatability. New documents should be authored using attr_lists. However,
+numerious documents exist which have been using the old attribute format for many
+years. This extension can be used to continue to render those documents correctly.
+"""
+
+import re
+from markdown.treeprocessors import Treeprocessor, isString
+from markdown.extensions import Extension
+
+
+ATTR_RE = re.compile("\{@([^\}]*)=([^\}]*)}")  # {@id=123}
+
+
+class LegacyAttrs(Treeprocessor):
+    def run(self, doc):
+        """Find and set values of attributes ({@key=value}). """
+        for el in doc.iter():
+            alt = el.get('alt', None)
+            if alt is not None:
+                el.set('alt', self.handleAttributes(el, alt))
+            if el.text and isString(el.text):
+                el.text = self.handleAttributes(el, el.text)
+            if el.tail and isString(el.tail):
+                el.tail = self.handleAttributes(el, el.tail)
+
+    def handleAttributes(self, el, txt):
+        """ Set attributes and return text without definitions. """
+        def attributeCallback(match):
+            el.set(match.group(1), match.group(2).replace('\n', ' '))
+        return ATTR_RE.sub(attributeCallback, txt)
+
+
+class LegacyAttrExtension(Extension):
+    def extendMarkdown(self, md, md_globals):
+        la = LegacyAttrs(md)
+        md.treeprocessors.add('legacyattrs', la, '>inline')
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return LegacyAttrExtension(**kwargs)