Skip Haddock for GHC 8.6.5

[parsonsmatt]

GHC 8.6.5 is broken with module re-exports. We can either re-export everything, or just skip building Haddock. I'd rather skip building Haddocks for an old GHC than make the code experience worse, or more fragile.

Before submitting your PR, check that you've:

• Bumped the version number.
• Documented new APIs with Haddock markup.
• Added @since declarations to the Haddock.
• Ran stylish-haskell and otherwise adhered to the style guide.

After submitting your PR:

• Update the Changelog.md file with a link to your PR.
• Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts).

[belevy]

So were just dropping support for haddock in 8.6.5? What is support "policy" for GHC versions?

[parsonsmatt]

Here's the error we get:

esqueleto            >   Missing documentation for:
esqueleto            >     ExprParser (src/Database/Esqueleto/Internal/ExprParser.hs:53)
esqueleto            >     onExpr (src/Database/Esqueleto/Internal/ExprParser.hs:55)
esqueleto            >     skipToEscape (src/Database/Esqueleto/Internal/ExprParser.hs:62)
esqueleto            >     parseEscapedIdentifier (src/Database/Esqueleto/Internal/ExprParser.hs:65)
esqueleto            >     parseTableAccess (src/Database/Esqueleto/Internal/ExprParser.hs:72)
esqueleto            >     parseEscapedChars (src/Database/Esqueleto/Internal/ExprParser.hs:79)
esqueleto            > haddock: internal error: internal: extractDecl
esqueleto            > CallStack (from HasCallStack):
esqueleto            >   error, called at utils/haddock/haddock-api/src/Haddock/Interface/Create.hs:1116:12 in main:Haddock.Interface.Create

It's a Haddock bug that we're somehow getting triggered.

Seems related to this issue, which indicates that Haddock is just broken here for GHC 8.6 (see this comment. The fix is dropping the module re-export and replacing with an explicit export list.

But GHC 8.6.5 itself isn't hard to support, so I'm not terribly worried about keeping it around. If it does become a trouble, then we'll drop it. I think it makes sense to retain support for GHC 8.10.7 until people aren't using it much, which will be a while.

[parsonsmatt]

if anyone is seeing this and wondering why, i'd be happy to accept a PR that just fixes it and re-enables, fwiw