HIE should generate local Hoogle database

[infinisil]

It makes sense for HIE to generate the hoogle database itself, locally in the project, because:

• Better UX, because users won't have to fiddle with it on their own
• All users get the full features, without having to worry about it
• Hoogle can be made to generate all and only those packages the user has in their project. No need to generate all stackage packages if you don't use most of them, and users might use packages not in stackage.
• Hoogle database won't get out of date
• No global ~/.hoogle needed, every project can have their own hoogle database
• Will always have the right package versions available in the database, which can be different for projects

(Correct me if some of those don't hold)

This should be implemented by having HIE generate the database in the background and having a status indicator like "Indexing packages.." that indicates that not all features are available until it's done.

Ping @fendor

[lukel97]

This makes a lot of sense to me. Generating the hoogle database can take a couple of minutes though. Is there any disadvantage to sharing a global hoogle database?

[nponeccop]

Is there any disadvantage to sharing a global hoogle database?

Different versions of the same package in different projects?

[lorenzo]

I’m in favor of doing this, I get bitten by the lack of a proper Hoogle database constantly

[lukel97]

Is there any disadvantage to sharing a global hoogle database?

Different versions of the same package in different projects?

I think at the moment the README.md just tells people to run hoogle generate, and it turns that just generates a database for the current version of Stackage LTS. Looks like there's also a --local option but that only generates links for packages built with documentation, so the user would need to have that turned on in their config (or could we specify it ghc-mod/hie-bios?)

[lorenzo]

We can certainly add extra dynamicsc flags with ghc-mod

[wz1000]

To generate a local/project specific hoogle database, both stack and cabal first need to generate haddock documentation. However, if haddock documentation is available, HIE will try to use that instead of hoogle, as it is generally more accurate and preserves the original markup. So I don't see the point of generating local hoogle dbs.

The global hoogle db is meant to be a fallback to when local haddock documentation is not available, as it is often slow and unreliable to generate haddock docs.

[fendor]

HsImport uses the hoogle db. I dont know how this change would affect the plugin. If only local/installed packages are searched, it may impact the search results of hoogle.

[jneira]

So afaiu hie will use the local generated haddock docs so the option could be make hie generate them. But that should be done on demand, to recreate it only when needed. Not sure if there would be a reliable way to know when the docs should be regenerated. Otoh users can always use cabal or stack themselves to do it.
So not sure if documenting it would be enough or show a warning to users to let then know why document on hover is not working and how to fix i . @infinisil what do you think?