Use munch1 to parse Language (#8508)

* Add regression test for #8507

* Use munch1 to parse Language

If you use `some anyChar` trailing whitespace will be
part of the parsed value, see #8507.

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

Author: ffaf1

Cabal-syntax/src/Language/Haskell/Extension.hs

@@ -77,7 +77,7 @@ instance Pretty Language where
   pretty other                   = Disp.text (show other)
 
 instance Parsec Language where
-  parsec = classifyLanguage <$> P.some P.anyChar
+  parsec = classifyLanguage <$> P.munch1 isAlphaNum
 
 classifyLanguage :: String -> Language
 classifyLanguage = \str -> case lookup str langTable of

cabal-testsuite/PackageTests/Regression/T8507/Foo.hs

@@ -0,0 +1,4 @@
+module Foo where
+
+foo :: a
+foo = undefined

cabal-testsuite/PackageTests/Regression/T8507/cabal.out

@@ -0,0 +1,8 @@
+# cabal v2-build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - pkg-0 (lib) (first run)
+Configuring library for pkg-0..
+Preprocessing library for pkg-0..
+Building library for pkg-0..

cabal-testsuite/PackageTests/Regression/T8507/cabal.project

@@ -0,0 +1,2 @@
+packages:
+  ./

cabal-testsuite/PackageTests/Regression/T8507/cabal.test.hs

@@ -0,0 +1,6 @@
+import Test.Cabal.Prelude
+
+-- Issue #8507: trailing space in `default-language` should not make
+-- `cabal build` complain.
+main = cabalTest $ cabal "v2-build" ["all"]
+

cabal-testsuite/PackageTests/Regression/T8507/pkg.cabal

@@ -0,0 +1,14 @@
+cabal-version: 3.0
+name: pkg
+synopsis: synopsis
+description: description
+version: 0
+category: example
+maintainer: [email protected]
+license: GPL-3.0-or-later
+
+library
+  exposed-modules: Foo,
+  build-depends: base == 4.*
+  default-language: Haskell2010    
+    -- Note whitespace after “Haskell 2010”.

fix-whitespace.yaml

@@ -92,6 +92,7 @@ excluded-files:
   - Cabal-syntax/src/Distribution/Fields/Lexer.hs
   - Cabal-tests/tests/ParserTests/warnings/tab.cabal
   - Cabal-tests/tests/ParserTests/warnings/utf8.cabal
+  - cabal-testsuite/PackageTests/Regression/T8507/pkg.cabal
 
   # These also contain tabs that affect the golden value:
   # Could be removed from exceptions, but then the tab warning