Fixes <https://debbugs.gnu.org/32387>.
* guix/import/cabal.scm (eval-cabal): Avoid mis-match when the custom-setup
section cannot be created.
* guix/import/hackage.scm (cabal-custom-setup-dependencies->names): Do not
crash when cabal-package-custom-setup returns #F.
* guix/import/cabal.scm (eval-cabal): Modify.
* tests/hackage.scm (test-cabal-4): New variable and test.
(test-cabal-5): New variable and test.
(test-cabal-6): New variable and test.
* guix/import/cabal.scm (make-cabal-parser): Modify.
(is-any): New variable.
(is-none): New variable.
(lex-any): New procedure.
(lex-none): New procedure.
(lex-word): Modify.
(eval-cabal): Modify.
* guix/packages.scm <package>: Use '@' in record printer.
* guix/import/cabal.scm <cabal-package>: Likewise
* guix/import/elpa.scm <elpa-package>: Likewise.
* tests/packages.scm: Adapt to it.
* guix/import/cabal.scm (is-test): Allow spaces between keyword and
parentheses.
(is-id): Add argument 'port'. Allow spaces between keyword and column.
(lex-word): Adjust call to 'is-id'.
* guix/import/cabal.scm (is-true, is-false, lex-true, lex-false): New procedures.
(lex-word): Use them.
(make-cabal-parser): Add TRUE and FALSE tokens.
(eval): Add entries for 'true and 'false symbols.
* guix/import/cabal.scm: New file.
* guix/import/hackage.scm: Update to use the new Cabal parsing module.
* tests/hackage.scm: Update tests.
* guix/scripts/import/hackage.scm: Add new '--cabal-environment' and '--stdin'
options.
* doc/guix.texi: ... and document them.
* Makefile.am (MODULES): Add 'guix/import/cabal.scm',
'guix/import/hackage.scm' and 'guix/scripts/import/hackage.scm'.
(SCM_TESTS): Add 'tests/hackage.scm'.
Ricardo Wurmus