bpo-47227: Suppress expression chaining for more RE parsing errors (GH-32333)

serhiy-storchaka · web-flow · commit 50872dbadcba · 2022-04-06T19:54:44.000+03:00
diff --git a/Lib/re/_parser.py b/Lib/re/_parser.py
@@ -335,7 +335,7 @@ def _class_escape(source, escape):
                 c = ord(unicodedata.lookup(charname))
             except KeyError:
                 raise source.error("undefined character name %r" % charname,
-                                   len(charname) + len(r'\N{}'))
+                                   len(charname) + len(r'\N{}')) from None
             return LITERAL, c
         elif c in OCTDIGITS:
             # octal escape (up to three digits)
@@ -395,7 +395,7 @@ def _escape(source, escape, state):
                 c = ord(unicodedata.lookup(charname))
             except KeyError:
                 raise source.error("undefined character name %r" % charname,
-                                   len(charname) + len(r'\N{}'))
+                                   len(charname) + len(r'\N{}')) from None
             return LITERAL, c
         elif c == "0":
             # octal escape
@@ -1014,7 +1014,7 @@ def addgroup(index, pos):
                     try:
                         index = groupindex[name]
                     except KeyError:
-                        raise IndexError("unknown group name %r" % name)
+                        raise IndexError("unknown group name %r" % name) from None
                 else:
                     try:
                         index = int(name)
@@ -1053,7 +1053,7 @@ def addgroup(index, pos):
                     this = chr(ESCAPES[this][1])
                 except KeyError:
                     if c in ASCIILETTERS:
-                        raise s.error('bad escape %s' % this, len(this))
+                        raise s.error('bad escape %s' % this, len(this)) from None
                 lappend(this)
         else:
             lappend(this)
@@ -1074,5 +1074,5 @@ def expand_template(template, match):
         for index, group in groups:
             literals[index] = g(group) or empty
     except IndexError:
-        raise error("invalid group reference %d" % index)
+        raise error("invalid group reference %d" % index) from None
     return empty.join(literals)
diff --git a/Misc/NEWS.d/next/Library/2022-04-05-15-53-58.bpo-47227.1HWdp9.rst b/Misc/NEWS.d/next/Library/2022-04-05-15-53-58.bpo-47227.1HWdp9.rst
@@ -0,0 +1 @@
+Suppress expression chaining for more :mod:`re` parsing errors.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Suppress expression chaining for more :mod:`re` parsing errors.