Deprecate functions instead of directly removing them

Author: adithyaov

Changelog.md

@@ -4,22 +4,33 @@
 
 - Support for big-endian architectures.
 - Added `unicodeVersion`.
-- Added the module `Unicode.Char.Case.Compat`.
 - Added `GeneralCategory` data type and corresponding `generalCategoryAbbr`,
   `generalCategory` functions.
 - Added the following functions to `Unicode.Char.General`:
   `isAlphabetic`, `isAlphaNum`,
   `isControl`, `isMark`, `isPrint`, `isPunctuation`, `isSeparator`,
   `isSymbol` and `isWhiteSpace`.
 - Added the module `Unicode.Char.Numeric`.
-- **Breaking change:** Changed the behavior of `isLetter` and `isSpace` to match
-  `base`’s `Data.Char` behavior. Move these functions to the compatibility module
-  `Unicode.Char.General.Compat`. The previous behavior is obtained using
-  `isAlphabetic` and `isWhiteSpace` respectively.
+- Add compatibility modules:
+
+  - `Unicode.Char.General.Compat`
+  - `Unicode.Char.Case.Compat`
+
+  These modules are compatible with `base:Data.Char`.
 - Re-export some functions from `Data.Char` in order to make `Unicode.Char`
   a drop-in replacement.
 - Drop support for GHC 7.10.3
 
+### Deprecations
+
+- In `Unicode.Char.General`.
+
+  - `isLetter`
+  - `isSpace`
+
+  Preserve the behavior of these functions in `isAlphabetic` and `isWhiteSpace`
+  respectively.
+
 ## 0.2.0 (November 2021)
 
 * Update to [Unicode 14.0.0](https://www.unicode.org/versions/Unicode14.0.0/).

lib/Unicode/Char.hs

@@ -45,7 +45,7 @@ import Data.Char (chr, ord)
 import Data.Version (Version, makeVersion)
 import Unicode.Char.Case
 import Unicode.Char.Case.Compat
-import Unicode.Char.General
+import Unicode.Char.General hiding (isLetter, isSpace)
 import Unicode.Char.General.Compat
 import Unicode.Char.Identifiers
 import Unicode.Char.Numeric

lib/Unicode/Char/General.hs

@@ -26,6 +26,8 @@ module Unicode.Char.General
     , isSeparator
     , isSymbol
     , isWhiteSpace
+    , isLetter
+    , isSpace
     -- ** Re-export
     , isAscii
     , isLatin1
@@ -428,6 +430,23 @@ isSymbol c = case generalCategory c of
     OtherSymbol    -> True
     _              -> False
 
+-- | Returns 'True' for alphabetic Unicode characters.
+--
+-- @since 0.1.0
+{-# INLINE isLetter #-}
+{-# DEPRECATED isLetter "Use isAlphabetic instead. Note that the behavior of this function does not match base:Data.Char.isLetter. See Unicode.Char.General.Compat for behavior compatible with base:Data.Char." #-}
+isLetter :: Char -> Bool
+isLetter = P.isAlphabetic
+
+-- | Returns 'True' for any whitespace characters, and the control
+-- characters @\\t@, @\\n@, @\\r@, @\\f@, @\\v@.
+--
+-- @since 0.1.0
+{-# INLINE isSpace #-}
+{-# DEPRECATED isSpace "Use isWhiteSpace instead. Note that the behavior of this function does not match base:Data.Char.isSpace. See Unicode.Char.General.Compat for behavior compatible with base:Data.Char." #-}
+isSpace :: Char -> Bool
+isSpace = P.isWhite_Space
+
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 -- Korean Hangul
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