bpo-36548: Improve the repr of re flags. (GH-12715)

2 files changed, 44 insertions, 16 deletions

diff --git a/Lib/re.py b/Lib/re.py
index 68d62dc..8f1d55d 100644
--- a/Lib/re.py
+++ b/Lib/re.py
@@ -141,24 +141,40 @@ __all__ = [
 __version__ = "2.2.1"
 
 class RegexFlag(enum.IntFlag):
-    ASCII = sre_compile.SRE_FLAG_ASCII # assume ascii "locale"
-    IGNORECASE = sre_compile.SRE_FLAG_IGNORECASE # ignore case
-    LOCALE = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
-    UNICODE = sre_compile.SRE_FLAG_UNICODE # assume unicode "locale"
-    MULTILINE = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
-    DOTALL = sre_compile.SRE_FLAG_DOTALL # make dot match newline
-    VERBOSE = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments
-    A = ASCII
-    I = IGNORECASE
-    L = LOCALE
-    U = UNICODE
-    M = MULTILINE
-    S = DOTALL
-    X = VERBOSE
+    ASCII = A = sre_compile.SRE_FLAG_ASCII # assume ascii "locale"
+    IGNORECASE = I = sre_compile.SRE_FLAG_IGNORECASE # ignore case
+    LOCALE = L = sre_compile.SRE_FLAG_LOCALE # assume current 8-bit locale
+    UNICODE = U = sre_compile.SRE_FLAG_UNICODE # assume unicode "locale"
+    MULTILINE = M = sre_compile.SRE_FLAG_MULTILINE # make anchors look for newline
+    DOTALL = S = sre_compile.SRE_FLAG_DOTALL # make dot match newline
+    VERBOSE = X = sre_compile.SRE_FLAG_VERBOSE # ignore whitespace and comments
     # sre extensions (experimental, don't rely on these)
-    TEMPLATE = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking
-    T = TEMPLATE
+    TEMPLATE = T = sre_compile.SRE_FLAG_TEMPLATE # disable backtracking
     DEBUG = sre_compile.SRE_FLAG_DEBUG # dump pattern after compilation
+
+    def __repr__(self):
+        if self._name_ is not None:
+            return f're.{self._name_}'
+        value = self._value_
+        members = []
+        negative = value < 0
+        if negative:
+            value = ~value
+        for m in self.__class__:
+            if value & m._value_:
+                value &= ~m._value_
+                members.append(f're.{m._name_}')
+        if value:
+            members.append(hex(value))
+        res = '|'.join(members)
+        if negative:
+            if len(members) > 1:
+                res = f'~({res})'
+            else:
+                res = f'~{res}'
+        return res
+    __str__ = object.__str__
+
 globals().update(RegexFlag.__members__)
 
 # sre exception
diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index 137c31d..4817d76 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -2170,6 +2170,18 @@ class PatternReprTests(unittest.TestCase):
         self.assertEqual(r[:30], "re.compile('Very long long lon")
         self.assertEqual(r[-16:], ", re.IGNORECASE)")
 
+    def test_flags_repr(self):
+        self.assertEqual(repr(re.I), "re.IGNORECASE")
+        self.assertEqual(repr(re.I|re.S|re.X),
+                         "re.IGNORECASE|re.DOTALL|re.VERBOSE")
+        self.assertEqual(repr(re.I|re.S|re.X|(1<<20)),
+                         "re.IGNORECASE|re.DOTALL|re.VERBOSE|0x100000")
+        self.assertEqual(repr(~re.I), "~re.IGNORECASE")
+        self.assertEqual(repr(~(re.I|re.S|re.X)),
+                         "~(re.IGNORECASE|re.DOTALL|re.VERBOSE)")
+        self.assertEqual(repr(~(re.I|re.S|re.X|(1<<20))),
+                         "~(re.IGNORECASE|re.DOTALL|re.VERBOSE|0x100000)")
+
 
 class ImplementationTest(unittest.TestCase):
     """