Unified choice of binding category between TH and CLI

[edsko]

[dschrempf]

Related to

• Function pointer bindings should not have _ptr suffix #1262, and
• Golden tests should use multiple modules #1263

[dschrempf]

This ticket is about fine-grained selection of which binding category to create bindings for. At the moment, we only allow the specification of the Safety; instead, we want to specify something like

newtype ByCategory a = ByCategory { unByCategory :: Map BindingCategory a }
  deriving newtype (Functor, Foldable, Show)

type Predicate = ???

type SelectByCategory = ByCategory Predicate

[dschrempf]

I am pondering on this ticket. Some observations:

I suggest performing the "category selection" (not to be confused with the Select pass) as late as possible (right before translating the module to a string-like object).

Hence, the types we want are something like

-- At the latest stage we have `SDecl`s.
type Predicate = SDecl -> Maybe SDecl
type SelectByCategory = ByCategory Predicate

-- `SDecl` may be too complicated, or we may not want to expose it, then we
-- could use names (I guess `HsBindgen.Language.Haskell.Name`). By the way, is
-- there a function `f :: SDecl -> Name`?
type SimplePredicate = Name -> Bool
type SimpleSelectByCategory = ByCategory SimplePredicate

Then, we would apply the SelectByCategory or SimpleSelectByCategory before translating the module/modules to string-like form. For consistency, I suggest always doing this (i.e., when translating to a single module, and when translating to multiple modules).

The defaults will be:

• When translating to multiple modules, the predicate will always be Just decl (True).
• When translating to a single module, the predicate will be Just decl (True) for all categories but Unsafe.

The predicate will be user-configurable. That is, we add the predicate to HsBindgen.Config.Config, and the BackendConfig.

This means, that

• the artifact FinalDecls still contains all declarations, but
• FinalModule will not contain all declarations anymore, and
• FinalModules may not contain all declarations anymore.

The above makes me think that we have to distinguish between the single module and multiple module predicates (i.e., the predicates may be different, even for a single run).