Fix assertion failure when combining build-tool-depends and --enable-documentation

The `setDocumentation` function was modifying the elaborated package
after the hash was computed. This led to the assertion failing as the
computed hash was different to what was computed in the initial install
plan.

Therefore in order to fix this we either needed to:

1. Set elabBuildHaddocks = False at the point where the hash is
   initially computed.
2. Verify that elabBuildHaddocks = True will not lead to unexpected
   results.

The latter has been implemented.

The elabBuildHaddocks option is only consulted in
`hasValidHaddockTargets`, at which point documentation building the
executable component is disabled because elabHaddockExecutables is
False.

In the added test we ensure this by checking that we didn't build
documentation for the executable which is built because of
build-tool-depends.

Fixes haskell#6006 haskell#8313

Author: mpickering

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

@@ -258,7 +258,7 @@ sanityCheckElaboratedConfiguredPackage
   -> a
   -> a
 sanityCheckElaboratedConfiguredPackage
-  _sharedConfig
+  sharedConfig
   elab@ElaboratedConfiguredPackage{..} =
     ( case elabPkgOrComp of
         ElabPackage pkg -> sanityCheckElaboratedPackage elab pkg
@@ -273,9 +273,9 @@ sanityCheckElaboratedConfiguredPackage
       -- 'installedPackageId' we assigned is consistent with
       -- the 'hashedInstalledPackageId' we would compute from
       -- the elaborated configured package
-      -- . assert (isInplaceBuildStyle elabBuildStyle ||
-      --    elabComponentId == hashedInstalledPackageId
-      --                           (packageHashInputs sharedConfig elab))
+      . traceShow elabUnitId (assert (isInplaceBuildStyle elabBuildStyle ||
+         elabComponentId == hashedInstalledPackageId
+                                 (packageHashInputs sharedConfig elab)))
 
       -- the stanzas explicitly disabled should not be available
       . assert
@@ -3293,9 +3293,7 @@ pruneInstallPlanPass1 pkgs
     prune :: ElaboratedConfiguredPackage -> PrunedPackage
     prune elab = PrunedPackage elab' (pruneOptionalDependencies elab')
       where
-        elab' =
-          setDocumentation $
-            addOptionalStanzas elab
+        elab' = addOptionalStanzas elab
 
     graph = Graph.fromDistinctList pkgs'
 
@@ -3444,24 +3442,6 @@ pruneInstallPlanPass1 pkgs
             <> optionalStanzasWithDepsAvailable availablePkgs elab pkg
     addOptionalStanzas elab = elab
 
-    setDocumentation :: ElaboratedConfiguredPackage -> ElaboratedConfiguredPackage
-    setDocumentation elab@ElaboratedConfiguredPackage{elabPkgOrComp = ElabComponent comp} =
-      elab
-        { elabBuildHaddocks =
-            elabBuildHaddocks elab && documentationEnabled (compSolverName comp) elab
-        }
-      where
-        documentationEnabled c =
-          case c of
-            CD.ComponentLib -> const True
-            CD.ComponentSubLib _ -> elabHaddockInternal
-            CD.ComponentFLib _ -> elabHaddockForeignLibs
-            CD.ComponentExe _ -> elabHaddockExecutables
-            CD.ComponentTest _ -> elabHaddockTestSuites
-            CD.ComponentBench _ -> elabHaddockBenchmarks
-            CD.ComponentSetup -> const False
-    setDocumentation elab = elab
-
     -- Calculate package dependencies but cut out those needed only by
     -- optional stanzas that we've determined we will not enable.
     -- These pruned deps are not persisted in this pass since they're based on

cabal-testsuite/PackageTests/HaddockBuildDepends/a.cabal

@@ -0,0 +1,10 @@
+name: a
+version: 0.1.0.0
+build-type: Simple
+cabal-version: >= 1.10
+
+library
+    exposed-modules:  MyLib
+    build-depends:    base, lib
+    hs-source-dirs:   src
+    default-language: Haskell2010

cabal-testsuite/PackageTests/HaddockBuildDepends/cabal.project

@@ -0,0 +1 @@
+packages: .

cabal-testsuite/PackageTests/HaddockBuildDepends/cabal.test.hs

@@ -0,0 +1,22 @@
+import Test.Cabal.Prelude
+
+
+main = cabalTest . withRepo "repo" $ do
+    cabal "build" ["--enable-documentation"]
+
+    env <- getTestEnv
+    let storeDir = testCabalDir env </> "store"
+
+    -- Check properties of executable component
+    libDir <- liftIO $ findDependencyInStore storeDir "exe"
+    -- Documentation is enabled..
+    assertFileDoesContain (libDir </> "cabal-hash.txt") "documentation: True"
+    -- But not built
+    shouldDirectoryNotExist (  libDir </> "share" </> "doc" )
+
+    -- Check properties of library
+    libDir <- liftIO $ findDependencyInStore storeDir "lib"
+    -- Documentation is enabled..
+    assertFileDoesContain (libDir </> "cabal-hash.txt") "documentation: True"
+    -- and has been built
+    shouldDirectoryExist (  libDir </> "share" </> "doc" )

cabal-testsuite/PackageTests/HaddockBuildDepends/repo/exe-1/Main.hs

@@ -0,0 +1,3 @@
+module Main where
+
+main = return ()

cabal-testsuite/PackageTests/HaddockBuildDepends/repo/exe-1/exe.cabal

@@ -0,0 +1,12 @@
+name:                exe
+version:             1
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          [email protected]
+build-type:          Simple
+cabal-version:       2.0
+
+executable exe
+  build-depends:       base
+  main-is:             Main.hs
+  default-language:    Haskell2010

cabal-testsuite/PackageTests/HaddockBuildDepends/repo/lib-1/Lib.hs

@@ -0,0 +1 @@
+module Lib where

cabal-testsuite/PackageTests/HaddockBuildDepends/repo/lib-1/lib.cabal

@@ -0,0 +1,13 @@
+name:                lib
+version:             1
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          [email protected]
+build-type:          Simple
+cabal-version:       2.0
+
+library
+  build-depends:       base
+  build-tool-depends:  exe:exe
+  exposed-modules:     Lib
+  default-language:    Haskell2010

cabal-testsuite/PackageTests/HaddockBuildDepends/src/MyLib.hs

@@ -0,0 +1,4 @@
+module MyLib (someFunc) where
+
+someFunc :: IO ()
+someFunc = return ()