allow passing command line flags to haddock

[ghorn]

I would like to be able to pass --ignore-all-exports to haddock in order to display haddock comments on internal functions. Could a field be added to haskell_doc for passing additional flags? Or maybe just a boolean field for this flag if you're afraid of users trying to unsafely override flags.

[ghorn]

from https://www.haskell.org/haddock/doc/html/invoking.html:

--ignore-all-exports
Causes Haddock to behave as if every module has the ignore-exports attribute (Section 3.7, “Module Attributes”). This might be useful for generating implementation documentation rather than interface documentation, for example.

[guibou]

A bit of followup on that one.

This is a real pain. It is possible to set attributes to a rule which will be passed to the aspects (used by haskell_doc). However these attributes are limited: they must be a string from a finite list of possible values:

Public aspect attributes are of type string and are called parameters. Parameters must have avalues attribute specified on them. In this case we have a parameter called extension that is allowed to have ‘*’, ‘h’, or ‘cc’ as a value.

(from https://docs.bazel.build/versions/master/skylark/aspects.html)

That's by design in bazel.

PR #444 was a PR with a proof of concept of a limited set of arguments. It was closed because the solution was a HACK.

[mboes]

Yet another reason to change the design in the following way?

$ bazel build //some/package:target@doc

i.e. use implicit targets for API documentation, like we currently do for REPL's?