- Add tests that implementation is the same as Generic
- We save few seconds for people who don't compile tests
- Resolves #6001

Split fields related functionality out of `Distribution.Parsec`
namespace which is not left only to handle "scalar" values.
This separation highlights that we use `parsec` for *structure* (think
JSON), and the *values* of the fields (think e.g. dates in JSON).

- New top-level `Distribution.Fields` and `Distribution.Parsec` modules
  should include most things most people would need.
- Also `Distribution.Pretty.Field` is moved to `Distribution.Fields.Pretty`,
  as now it has proper place.
- The commit is moving things around and fixing compilation errors.
- I fixed `cabal check` parse error printing as I was nearby.

quasicomputational authored 6 years ago and Mikhail Glushenkov committed 6 years ago

This code existed to support building Cabal with 7.4 and earlier, but
we have recently dropped support for 7.4.

There are 3957 warned files atm in Hackage index.
All of them have tab "inside the field", thus old parser acceps them.

See e.g added th-lift-instances file. The warning comes from the description field.

Distribution.SDPX.LicenseId and Distribution.SDPX.LicenceExceptionId are
generated.

This commit reworks how GenericPackageDescription is parsed from
`[Field Position]` and pretty-printed to `Doc`.

This also fixes few issues:
- Fix #4697: `cabal format` doesn't output custom-setup stanza (nor
  foreign-lib stanzas)
- Fix #4719: `parse . pretty . parse = parse`  for all Hackage cabal files.
    - `parser-hackage-tests roundtrip` is the test program.

The handling of `license-file` and `license-files` is changed.
Now they behave the same.

At the moment we have very lax "name" lexer, which is essentially
*everything else* than otherwise specified characters: parens, space,
symbols (but not hyphen -)

This removes `TokNum` and `SecArgNum`, both are merged into `TokSym` and
`SecArgSym` respectively.

- Manually generate Lexer.hs
- Temporarily disable parser-hackage-tests on appveyor (needs
  01-index.tar)
- Add root Makefile to handle commmon dev tasks (genering Lexer.hs)