bpo-40066: [Enum] update str() and format() output (GH-30582)

Undo rejected PEP-663 changes:

- restore `repr()` to its 3.10 status
- restore `str()` to its 3.10 status

New changes:

- `IntEnum` and `IntFlag` now leave `__str__` as the original `int.__str__` so that str() and format() return the same result
- zero-valued flags without a name have a slightly changed repr(), e.g. `repr(Color(0)) == '<Color: 0>'`
- update `dir()` for mixed-in types to return all the methods and attributes of the mixed-in type
- added `_numeric_repr_` to `Flag` to control display of unnamed values
- enums without doc strings have a more comprehensive doc string added
- `ReprEnum` added -- inheriting from this makes it so only `__repr__` is replaced, not `__str__` nor `__format__`; `IntEnum`, `IntFlag`, and `StrEnum` all inherit from `ReprEnum`

1 files changed, 5 insertions, 1 deletions

diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index d5e2c52..8e4e648 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -1490,8 +1490,10 @@ class UnicodeTest(string_tests.CommonTest,
         # issue18780
         import enum
         class Float(float, enum.Enum):
+            # a mixed-in type will use the name for %s etc.
             PI = 3.1415926
         class Int(enum.IntEnum):
+            # IntEnum uses the value and not the name for %s etc.
             IDES = 15
         class Str(enum.StrEnum):
             # StrEnum uses the value and not the name for %s etc.
@@ -1508,8 +1510,10 @@ class UnicodeTest(string_tests.CommonTest,
         # formatting jobs delegated from the string implementation:
         self.assertEqual('...%(foo)s...' % {'foo':Str.ABC},
                          '...abc...')
+        self.assertEqual('...%(foo)r...' % {'foo':Int.IDES},
+                         '...<Int.IDES: 15>...')
         self.assertEqual('...%(foo)s...' % {'foo':Int.IDES},
-                         '...IDES...')
+                         '...15...')
         self.assertEqual('...%(foo)i...' % {'foo':Int.IDES},
                          '...15...')
         self.assertEqual('...%(foo)d...' % {'foo':Int.IDES},