Haddock errors are no longer fatal, but prevent common ones anyway

Haddock errors aren't fatal any more, but Cabal now knows not to invoke Haddock when there is no input for it to process.

Cabal/ChangeLog.md

@@ -1,4 +1,8 @@
 # 2.4.0.0 (current development version)
+  * `Distribution.Simple.Haddock` now checks to ensure that it 
+    does not erroneously call Haddock with no target modules. 
+    ([#5232](https://github.com/haskell/cabal/issues/5232), 
+    [#5459](https://github.com/haskell/cabal/issues/5459)).
   * Add more Lens combinators (`to`, `traversed`, `filtered`, 
     `non`) and an optic to access the modules in a component
     of a `PackageDescription` by the `ComponentName`.

Cabal/Distribution/Simple/Haddock.hs

@@ -525,15 +525,19 @@ runHaddock :: Verbosity
               -> ConfiguredProgram
               -> HaddockArgs
               -> IO ()
-runHaddock verbosity tmpFileOpts comp platform haddockProg args = do
-  let haddockVersion = fromMaybe (error "unable to determine haddock version")
-                       (programVersion haddockProg)
-  renderArgs verbosity tmpFileOpts haddockVersion comp platform args $
-    \(flags,result)-> do
-
-      runProgram verbosity haddockProg flags
-
-      notice verbosity $ "Documentation created: " ++ result
+runHaddock verbosity tmpFileOpts comp platform haddockProg args 
+  | null (argTargets args) = warn verbosity $
+       "Haddocks are being requested, but there aren't any modules given "
+    ++ "to create documentation for."
+  | otherwise = do
+    let haddockVersion = fromMaybe (error "unable to determine haddock version")
+                        (programVersion haddockProg)
+    renderArgs verbosity tmpFileOpts haddockVersion comp platform args $
+      \(flags,result)-> do
+
+        runProgram verbosity haddockProg flags
+
+        notice verbosity $ "Documentation created: " ++ result
 
 
 renderArgs :: Verbosity

Cabal/Distribution/Types/PackageDescription/Lens.hs

@@ -20,7 +20,7 @@ import Distribution.Types.Executable          (Executable, exeModules)
 import Distribution.Types.Executable.Lens     (exeName)
 import Distribution.Types.ForeignLib          (ForeignLib, foreignLibModules)
 import Distribution.Types.ForeignLib.Lens     (foreignLibName)
-import Distribution.Types.Library             (Library, allLibModules)
+import Distribution.Types.Library             (Library, explicitLibModules)
 import Distribution.Types.Library.Lens        (libName)
 import Distribution.Types.PackageDescription  (PackageDescription)
 import Distribution.Types.PackageId           (PackageIdentifier)
@@ -156,9 +156,9 @@ extraDocFiles f s = fmap (\x -> s { T.extraDocFiles = x }) (f (T.extraDocFiles s
 
 componentModules :: ComponentName -> AGetter PackageDescription [ModuleName]
 componentModules cname = case cname of
-    CLibName         -> library  . traversed . to allLibModules
+    CLibName         -> library  . traversed . to explicitLibModules
     CSubLibName name -> 
-      componentModules' name subLibraries (libName . non "") allLibModules
+      componentModules' name subLibraries (libName . non "") explicitLibModules
     CFLibName   name -> 
       componentModules' name foreignLibs  foreignLibName     foreignLibModules
     CExeName    name -> 

cabal-install/Distribution/Client/ProjectBuilding.hs

@@ -67,13 +67,15 @@ import           Distribution.Client.SourceFiles
 import           Distribution.Client.SrcDist (allPackageSourceFiles)
 import           Distribution.Client.Utils (removeExistingFile)
 
+import           Distribution.Compat.Lens
 import           Distribution.Package hiding (InstalledPackageId, installedPackageId)
 import qualified Distribution.PackageDescription as PD
 import           Distribution.InstalledPackageInfo (InstalledPackageInfo)
 import qualified Distribution.InstalledPackageInfo as Installed
 import           Distribution.Simple.BuildPaths (haddockDirName)
 import qualified Distribution.Simple.InstallDirs as InstallDirs
 import           Distribution.Types.BuildType
+import           Distribution.Types.PackageDescription.Lens (componentModules)
 import           Distribution.Simple.Program
 import qualified Distribution.Simple.Setup as Cabal
 import           Distribution.Simple.Command (CommandUI)
@@ -1049,8 +1051,8 @@ buildAndInstallUnpackedPackage verbosity
     isParallelBuild = buildSettingNumJobs >= 2
 
     whenHaddock action
-      | elabBuildHaddocks pkg = action
-      | otherwise             = return ()
+      | hasValidHaddockTargets pkg = action
+      | otherwise                  = return ()
 
     configureCommand = Cabal.configureCommand defaultProgramDb
     configureFlags v = flip filterConfigureFlags v $
@@ -1115,6 +1117,18 @@ buildAndInstallUnpackedPackage verbosity
         Just logFile -> withFile logFile AppendMode (action . Just)
 
 
+hasValidHaddockTargets :: ElaboratedConfiguredPackage -> Bool
+hasValidHaddockTargets pkg
+  | not (elabBuildHaddocks pkg) = False
+  | otherwise                   = any componentHasHaddocks components
+  where
+    components = elabHaddockTargets pkg
+    pd = elabPkgDescription pkg
+
+    componentHasHaddocks (ComponentTarget name _) = 
+      not (null (pd ^. componentModules name))
+
+
 buildInplaceUnpackedPackage :: Verbosity
                             -> DistDirLayout
                             -> BuildTimeSettings -> Lock -> Lock
@@ -1285,8 +1299,8 @@ buildInplaceUnpackedPackage verbosity
       | otherwise                     = action
 
     whenHaddock action
-      | elabBuildHaddocks pkg = action
-      | otherwise            = return ()
+      | hasValidHaddockTargets pkg = action
+      | otherwise                  = return ()
 
     whenReRegister  action
       = case buildStatus of

cabal-install/Distribution/Client/ProjectOrchestration.hs

@@ -140,8 +140,7 @@ import           Distribution.Simple.Command (commandShowOptions)
 import           Distribution.Simple.Configure (computeEffectiveProfiling)
 
 import           Distribution.Simple.Utils
-                   ( die'
-                   , notice, noticeNoWrap, debugNoWrap )
+                   ( die', warn, notice, noticeNoWrap, debugNoWrap )
 import           Distribution.Verbosity
 import           Distribution.Text
 import           Distribution.Simple.Compiler
@@ -940,7 +939,7 @@ dieOnBuildFailures verbosity plan buildOutcomes
 
        -- For all failures, print either a short summary (if we showed the
        -- build log) or all details
-       die' verbosity $ unlines
+       dieIfNotHaddockFailure verbosity $ unlines
          [ case failureClassification of
              ShowBuildSummaryAndLog reason _
                | verbosity > normal
@@ -969,6 +968,15 @@ dieOnBuildFailures verbosity plan buildOutcomes
            maybeToList (InstallPlan.lookup plan pkgid)
       ]
 
+    dieIfNotHaddockFailure
+      | all isHaddockFailure failuresClassification = warn
+      | otherwise                                   = die'
+      where
+        isHaddockFailure (_, ShowBuildSummaryOnly   (HaddocksFailed _)  ) = True
+        isHaddockFailure (_, ShowBuildSummaryAndLog (HaddocksFailed _) _) = True
+        isHaddockFailure _                                                = False
+
+
     classifyBuildFailure :: BuildFailure -> BuildFailurePresentation
     classifyBuildFailure BuildFailure {
                            buildFailureReason  = reason,

cabal-install/changelog

@@ -1,6 +1,9 @@
 -*-change-log-*-
 
 2.4.0.0 (current development version)
+	* 'new-build' now treats Haddock errors non-fatally. In addition,
+	  it attempts to avoid trying to generate Haddocks when there is
+	  nothing to generate them from. (#5232, #5459)
 	* 'new-run', 'new-test', and 'new-bench' now will attempt to resolve
 	  ambiguous selectors by filtering out selectors that would be invalid.
 	  (#4679, #5461)