Fix #789: ``:samp:`` role supports to escape curly braces with backslash

1 files changed, 37 insertions, 10 deletions

diff --git a/sphinx/roles.py b/sphinx/roles.py
index 2971c8fc3..453eb5aa0 100644
--- a/sphinx/roles.py
+++ b/sphinx/roles.py
@@ -284,6 +284,7 @@ def menusel_role(typ, rawtext, text, lineno, inliner, options={}, content=[]):
 
 
 _litvar_re = re.compile('{([^}]+)}')
+parens_re = re.compile(r'(\\*{|\\*})')
 
 
 def emph_literal_role(typ, rawtext, text, lineno, inliner,
@@ -296,17 +297,43 @@ def emph_literal_role(typ, rawtext, text, lineno, inliner,
     else:
         typ = typ.lower()
 
-    text = utils.unescape(text)
-    pos = 0
     retnode = nodes.literal(role=typ.lower(), classes=[typ])
-    for m in _litvar_re.finditer(text):  # type: ignore
-        if m.start() > pos:
-            txt = text[pos:m.start()]
-            retnode += nodes.Text(txt, txt)
-        retnode += nodes.emphasis(m.group(1), m.group(1))
-        pos = m.end()
-    if pos < len(text):
-        retnode += nodes.Text(text[pos:], text[pos:])
+    parts = list(parens_re.split(utils.unescape(text)))
+    stack = ['']
+    for part in parts:
+        matched = parens_re.match(part)
+        if matched:
+            backslashes = len(part) - 1
+            if backslashes % 2 == 1:    # escaped
+                stack[-1] += "\\" * int((backslashes - 1) / 2) + part[-1]
+            elif part[-1] == '{':       # rparen
+                stack[-1] += "\\" * int(backslashes / 2)
+                if len(stack) >= 2 and stack[-2] == "{":
+                    # nested
+                    stack[-1] += "{"
+                else:
+                    # start emphasis
+                    stack.append('{')
+                    stack.append('')
+            else:                       # lparen
+                stack[-1] += "\\" * int(backslashes / 2)
+                if len(stack) == 3 and stack[1] == "{" and len(stack[2]) > 0:
+                    # emphasized word found
+                    if stack[0]:
+                        retnode += nodes.Text(stack[0], stack[0])
+                    retnode += nodes.emphasis(stack[2], stack[2])
+                    stack = ['']
+                else:
+                    # emphasized word not found; the rparen is not a special symbol
+                    stack.append('}')
+                    stack = [''.join(stack)]
+        else:
+            stack[-1] += part
+    if ''.join(stack):
+        # remaining is treated as Text
+        text = ''.join(stack)
+        retnode += nodes.Text(text, text)
+
     return [retnode], []