Revert "cabal-install configureCompiler: configure progdb"

This reverts commit 8bdda9c.

In configureCompiler the call to configureAllKnownPrograms was too
eager. When called it selected the version of tools from PATH (such as
alex), and then when a package was configured these tools were passed
using `--with-alex` options to configure, which meant that the
build-tool-depends versions were not used. (See #10692)

Why was this call introduced in the first place? Because
configureCompiler would a different result depending on whether:

* It is run for the first time, the `ProgramDb` will contain
  unconfigured programs.
* It is run subsequently, `ProgramDb` is read from disk, it does not
  contain unconfigured programs.

Reverting this commit rexposes the bug that the serialised ProgramDb
will not contain UnconfiguredPrograms (in the case where reconfiguring
is avoided).

However, there are no code paths which require this logic in
`cabal-install` currently. The configuration phase happens again each
time that `Cabal` is called, with a populated `ProgramDb`. We will
fix this before the next major `cabal-install` release, but it would not
be suitable to backport.

In the future we will fix this properly by refactoring
`configureCompiler` so that `ProgramDb` is not serialised. The general
approach will be to make `configCompilerEx` return a pair of configured
programs (`ghc` and `ghc-pkg`) and expose an additional function from
`Cabal` which uses these two programs to perform the modifications to
the `ProgramDb` which `configCompilerEx` performs.

Also see #2238 and #9840

Fixes #10692

Author: mpickering

cabal-install/src/Distribution/Client/ProjectPlanning.hs

@@ -484,6 +484,7 @@ configureCompiler
     let fileMonitorCompiler = newFileMonitor $ distProjectCacheFile "compiler"
 
     progsearchpath <- liftIO $ getSystemSearchPath
+
     rerunIfChanged
       verbosity
       fileMonitorCompiler
@@ -499,7 +500,7 @@ configureCompiler
         let extraPath = fromNubList packageConfigProgramPathExtra
         progdb <- liftIO $ prependProgramSearchPath verbosity extraPath [] defaultProgramDb
         let progdb' = userSpecifyPaths (Map.toList (getMapLast packageConfigProgramPaths)) progdb
-        (comp, plat, progdb'') <-
+        result@(_, _, progdb'') <-
           liftIO $
             Cabal.configCompilerEx
               hcFlavor
@@ -516,12 +517,11 @@ configureCompiler
         -- programs it cares about, and those are the ones we monitor here.
         monitorFiles (programsMonitorFiles progdb'')
 
-        -- Configure the unconfigured programs in the program database,
-        -- as we can't serialise unconfigured programs.
-        -- See also #2241 and #9840.
-        finalProgDb <- liftIO $ configureAllKnownPrograms verbosity progdb''
+        -- Note: There is current a bug here where if reconfiguring is avoided,
+        -- the returned 'ProgramDb' will not contain `UnconfiguredPrograms` (but it will
+        -- on the fresh run). See #9840 for the ticket which tracks the problem.
 
-        return (comp, plat, finalProgDb)
+        return result
     where
       hcFlavor = flagToMaybe projectConfigHcFlavor
       hcPath = flagToMaybe projectConfigHcPath

cabal-testsuite/PackageTests/ExtraProgPath/setup.out

@@ -1,8 +1,10 @@
 # cabal v2-build
-Warning: cannot determine version of <ROOT>/pkg-config :
-""
 Configuration is affected by the following files:
 - cabal.project
+Warning: cannot determine version of <ROOT>/pkg-config :
+""
+Warning: cannot determine version of <ROOT>/pkg-config :
+""
 Resolving dependencies...
 Error: [Cabal-7107]
 Could not resolve dependencies: