Re: Migration guide for multiple home units

PUBLIC Thanks, based on this I got things going. I might have to come back to you if it turns out something's still broken in my original full application. -----Original Message----- From: Matthew Pickering Sent: Tuesday, June 21, 2022 12:54 AM To: Erdi, Gergo Cc: ÉRDI Gergo ; GHC Devs ; Montelatici, Raphael Laurent Subject: [External] Re: Migration guide for multiple home units My issue was caused by running the program in a dirty tree :) Find the modified program here - https://clicktime.symantec.com/39Wzk4MM32vW4JJm9h9nYC96xn?u=https%3A%2F%2Fgi... I compiled it with HEAD. Hope you can make sense of it, I think it's simpler than before. Cheers, Matt On Mon, Jun 20, 2022 at 5:47 PM Matthew Pickering wrote:

Gergo, I rewrote your example program for the new API but didn't quite manage to finish today. I will finish it off and post it tomorrow.

Matt

On Mon, Jun 20, 2022 at 6:16 AM Erdi, Gergo wrote:

...

PUBLIC

I managed to get this working, but I would like some feedback from Matt or others on whether this is the intended way of doing this.

1. The `extendMG` change can be brute-forced just to keep things going, by looking up dependency `ModSummary`s by `ModName` (we don't have full `Module`s at this point yet!):

registerModSummary :: (GhcMonad m) => ModSummary -> m () registerModSummary ms = modifySession \env -> let mg = hsc_mod_graph env -- TODO: of course with a bit more housekeeping we can do better than this... edges = [ NodeKey_Module $ msKey ms' | dep <- deps, ms' <- mgModSummaries mg, ms_mod_name ms' == dep ] mg' = extendMG mg edges ms in env{ hsc_mod_graph = mg' } where deps = map (unLoc . snd) $ ms_textual_imps ms

2. `registerModule` can be kept mostly as-is, since it only uses `modifyUnitState` to change the active unit:

registerModule :: (GhcMonad m) => ModDetails -> ModIface -> m () registerModule details iface = modifySession $ extendHpt . addModule where hmi = HomeModInfo iface details Nothing

mod = mi_module iface modOrig = ModOrigin (Just True) [] [] True

addModule = modifyUnitState $ \us -> us { moduleNameProvidersMap = M.insert (moduleName mod) (M.singleton mod modOrig) $ moduleNameProvidersMap us }

extendHpt = hscUpdateHUG $ addHomeModInfoToHug hmi

modifyUnitState :: (UnitState -> UnitState) -> HscEnv -> HscEnv modifyUnitState f env = env { hsc_unit_env = let ue = hsc_unit_env env in let units = ue_units ue units' = f units in ue_setUnits units' ue }

3. The tricky part is getting `addUnit` right. For this, based on the implementation of `initUnits`, I came up with the following:

modifyUnitEnv :: (UnitEnv -> UnitEnv) -> HscEnv -> HscEnv modifyUnitEnv f env = env { hsc_unit_env = let ue = hsc_unit_env env in f ue }

addUnit :: DynFlags -> UnitId -> HscEnv -> HscEnv addUnit dflags unitId = modifyUnitEnv $ \ue -> let dbs = ue_unit_dbs ue unit_state = ue_units ue home_unit = ue_homeUnit ue in flip updateHug ue $ unitEnv_insert unitId $ HomeUnitEnv { homeUnitEnv_units = unit_state , homeUnitEnv_unit_dbs = dbs , homeUnitEnv_dflags = dflags , homeUnitEnv_hpt = emptyHomePackageTable , homeUnitEnv_home_unit = home_unit }

setCurrentUnit :: UnitId -> HscEnv -> HscEnv setCurrentUnit unitId = modifyUnitEnv $ ue_setActiveUnit unitId

So my questions about this:

1. How does setting the home unit make sense? By doing this, I am effectively setting the home unit to `main` for all units, since that's the initial `ue_homeUnit` of the initial unit environment. Or does it not matter because after `addUnit`, I call `setCurrentUnit` anyway? I've found that I can't use the unit I am just adding as its own home unit, because that then leads to module name resolution problems in `main`: every imported module from `main` is searched for in `main` instead of its correct unit.

2. Speaking of `main`, why is it that when adding units, I have to skip `mainUnitId`, otherwise module resolution breaks again?

3. Unlike the previous version, I am no longer creating and putting `UnitInfo`s anywhere. Where is this going to bite me? Where (if anywhere) should I put `UnitInfo`s with the new setup?

Thanks, Gergo

-----Original Message----- From: ÉRDI Gergő Sent: Sunday, June 19, 2022 12:32 PM To: Erdi, Gergo Cc: GHC Devs ; Montelatici, Raphael Laurent Subject: [External] Re: Migration guide for multiple home units

On Thu, 16 Jun 2022, Erdi, Gergo via ghc-devs wrote:

...

Is there a migration guide for GHC API clients for the new “multiple home units” feature?

OK so in concrete terms, please see my attached program which is a heavily cut-down, standalone version of my real program. On commit fd42ab5fa1df847a6b595dfe4b63d9c7eecbf400^ (i.e. 3219610e3ba6cb6a5cd1f4e32e2b4befea5bd384) it compiles and works as expected. On commit fd42ab5fa1df847a6b595dfe4b63d9c7eecbf400 onwards, two problems pop up:

1. `extendMG` has changed and now requires manually specifying outgoing dependency edges. I thought the whole point of `summariseFile` was to collect this information? The reason I need to `extendMG` at that point is to get intra-unit orphan instances working.

2. `modifyUnitState` and its two uses (`addUnit` and `registerModule`) need to be updated to the new API. I think it makes sense that these need changing, since they touch exactly on the issue of which units are being compiled right now. However, I don't know how to update these. Also, I guess `setHomeUnit` should change the `CurrentUnit` instead of the `HomeUnit` now?

Thanks, Gergo

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