From bdf07b8cb3a910238b574bb1be8b9f80f521556b Mon Sep 17 00:00:00 2001
From: Anthony Sottile <asottile@umich.edu>
Date: Sun, 22 Mar 2020 12:43:34 -0700
Subject: [PATCH] fix expansion of regexes with regex-special characters

---
 babi/highlight.py       |  5 +++--
 babi/reg.py             |  7 +++++++
 tests/highlight_test.py | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/babi/highlight.py b/babi/highlight.py
index a32eb53..7b79c96 100644
--- a/babi/highlight.py
+++ b/babi/highlight.py
@@ -19,6 +19,7 @@ from babi.fdict import FDict
 from babi.reg import _Reg
 from babi.reg import _RegSet
 from babi.reg import ERR_REG
+from babi.reg import expand_escaped
 from babi.reg import make_reg
 from babi.reg import make_regset
 
@@ -418,7 +419,7 @@ class EndRule(NamedTuple):
         next_scope = scope + self.content_name
 
         boundary = match.end() == len(match.string)
-        reg = make_reg(match.expand(self.end))
+        reg = make_reg(expand_escaped(match, self.end))
         state = state.push(Entry(next_scope, self, reg, boundary))
         regions = _captures(compiler, scope, match, self.begin_captures)
         return state, True, regions
@@ -479,7 +480,7 @@ class WhileRule(NamedTuple):
         next_scope = scope + self.content_name
 
         boundary = match.end() == len(match.string)
-        reg = make_reg(match.expand(self.while_))
+        reg = make_reg(expand_escaped(match, self.while_))
         state = state.push_while(self, Entry(next_scope, self, reg, boundary))
         regions = _captures(compiler, scope, match, self.begin_captures)
         return state, True, regions
diff --git a/babi/reg.py b/babi/reg.py
index 79fa59a..14c73a0 100644
--- a/babi/reg.py
+++ b/babi/reg.py
@@ -1,4 +1,5 @@
 import functools
+import re
 from typing import Match
 from typing import Optional
 from typing import Tuple
@@ -7,6 +8,8 @@ import onigurumacffi
 
 from babi.cached_property import cached_property
 
+_BACKREF_RE = re.compile(r'((?<!\\)(?:\\\\)*)\\([0-9]+)')
+
 
 def _replace_esc(s: str, chars: str) -> str:
     """replace the given escape sequences of `chars` with \\uffff"""
@@ -142,6 +145,10 @@ class _RegSet:
                 return self._set_no_A_no_G.search(line, pos)
 
 
+def expand_escaped(match: Match[str], s: str) -> str:
+    return _BACKREF_RE.sub(lambda m: f'{m[1]}{re.escape(match[int(m[2])])}', s)
+
+
 make_reg = functools.lru_cache(maxsize=None)(_Reg)
 make_regset = functools.lru_cache(maxsize=None)(_RegSet)
 ERR_REG = make_reg(')this pattern always triggers an error when used(')
diff --git a/tests/highlight_test.py b/tests/highlight_test.py
index 5377ca3..bbd6a48 100644
--- a/tests/highlight_test.py
+++ b/tests/highlight_test.py
@@ -564,3 +564,18 @@ def test_rule_with_begin_and_no_end():
         Region(5, 7, ('test', 'bang', 'invalid')),
         Region(7, 8, ('test', 'bang', 'invalid')),
     )
+
+
+def test_begin_end_substitute_special_chars():
+    compiler, state = _compiler_state({
+        'scopeName': 'test',
+        'patterns': [{'begin': r'(\*)', 'end': r'\1', 'name': 'italic'}],
+    })
+
+    state, regions = highlight_line(compiler, state, '*italic*', True)
+
+    assert regions == (
+        Region(0, 1, ('test', 'italic')),
+        Region(1, 7, ('test', 'italic')),
+        Region(7, 8, ('test', 'italic')),
+    )