Add superscript plugin

Plugin ported from https://github.com/markdown-it/markdown-it-sup

Author: elijahgreenstein

mdit_py_plugins/superscript/__init__.py

@@ -0,0 +1,5 @@
+"""Superscript tag plugin, ported from Markdown-It."""
+
+from .index import superscript_plugin
+
+__all__ = ("superscript_plugin",)

mdit_py_plugins/superscript/index.py

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+"""Superscript tag plugin.
+
+Ported by Elijah Greenstein from https://github.com/markdown-it/markdown-it-sup
+cf. Subscript tag plugin, https://mdit-py-plugins.readthedocs.io/en/latest/#subscripts
+
+MIT License
+Copyright (c) 2014-2015 Vitaly Puzrin, Alex Kocharin.
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+from __future__ import annotations
+"""
+
+from collections.abc import Sequence
+import re
+from typing import TYPE_CHECKING
+
+from markdown_it import MarkdownIt
+from markdown_it.rules_inline import StateInline
+
+
+UNESCAPE_RE = re.compile(r"\\([ \\!\"#$%&'()*+,./:;<=>?@[\]^_`{|}~-])")
+WHITESPACE_RE = re.compile(r"(^|[^\\])(\\\\)*\s")
+
+
+def superscript_plugin(md: MarkdownIt) -> None:
+    """Superscript (``<sup>``) tag plugin for Markdown-It-Py.
+
+    This plugin is ported from `markdown-it-sup <https://github.com/markdown-it/markdown-it-sup>`_. Markup is based on the `Pandoc superscript extension <https://pandoc.org/MANUAL.html#superscripts-and-subscripts>`_.
+
+    Surround superscripted text with caret ``^`` characters. Superscripted text cannot contain whitespace characters. Nested markup is not supported.
+
+    Example usage:
+
+    >>> from markdown_it import MarkdownIt
+    >>> from mdit_py_plugins.superscript import superscript_plugin
+    >>> md = MarkdownIt().use(superscript_plugin)
+    >>> md.render("1^st^")
+    '<p>1<sup>st</sup></p>\\n'
+    >>> md.render("2^nd^")
+    '<p>2<sup>nd</sup></p>\\n'
+    """
+
+    def superscript(state: StateInline, silent: bool) -> bool:
+        """Parse inline text for superscripted text between caret ``^`` characters."""
+        maximum = state.posMax
+        start = state.pos
+
+        if ord(state.src[start]) != 0x5E:  # Check if char is `^`
+            return False
+        if silent:  # Do not run any pairs in validation mode
+            return False
+        if start + 2 >= maximum:
+            return False
+
+        state.pos = start + 1
+        found = False
+
+        while state.pos < maximum:
+            if ord(state.src[state.pos]) == 0x5E:  # Check if char is `^`
+                found = True
+                break
+            state.md.inline.skipToken(state)
+
+        if (not found) or (start + 1 == state.pos):
+            state.pos = start
+            return False
+
+        content = state.src[start + 1 : state.pos]
+
+        # Do not allow unescaped spaces/newlines inside
+        if WHITESPACE_RE.search(content) is not None:
+            state.pos = start
+            return False
+
+        # Found!
+        state.posMax = state.pos
+        state.pos = start + 1
+
+        # Earlier we checked !silent, but this implementation does not need it
+        token_so = state.push("sup_open", "sup", 1)
+        token_so.markup = "^"
+
+        token_t = state.push("text", "", 0)
+        token_t.content = UNESCAPE_RE.sub(r"\1", content)
+
+        token_sc = state.push("sup_close", "sup", -1)
+        token_sc.markup = "^"
+
+        state.pos = state.posMax + 1
+        state.posMax = maximum
+        return True
+
+    md.inline.ruler.after("emphasis", "sup", superscript)