Make cabal check warn about globs that don't match anything

These globs make `haddock`, `sdist` and `install` die, so they
definitely ought to be warned about!

Because of the dying behaviour, I made the checks dist-inexcusable;
starting from a clean slate I would probably have only made them
suspicious, but this isn't terrible.

Cabal/ChangeLog.md

@@ -68,6 +68,7 @@
     accepts a `Verbosity` argument.
   * `cabal check` now warns about globs that refer to missing
     directories.
+  * `cabal check` now warns about globs that do not match any files.
 
 ----
 

Cabal/Distribution/PackageDescription/Check.hs

@@ -2167,7 +2167,14 @@ checkGlobFiles :: Verbosity
 checkGlobFiles verbosity pkg root =
   fmap concat $ for allGlobs $ \(field, dir, glob) -> do
     results <- matchDirFileGlob' verbosity (specVersion pkg) (root </> dir) glob
-    return $ results >>= getWarning field glob
+    let individualWarnings = results >>= getWarning field glob
+        noMatchesWarning =
+          [ PackageDistInexcusable $
+                 "In '" ++ field ++ "': the pattern '" ++ glob ++ "' does not"
+              ++ " match any files."
+          | all (not . suppressesNoMatchesWarning) results
+          ]
+    return (noMatchesWarning ++ individualWarnings)
   where
     adjustedDataDir = if null (dataDir pkg) then "." else dataDir pkg
     allGlobs = concat
@@ -2175,6 +2182,15 @@ checkGlobFiles verbosity pkg root =
       , (,,) "extra-doc-files" "." <$> extraDocFiles pkg
       , (,,) "data-files" adjustedDataDir <$> dataFiles pkg
       ]
+
+    -- If there's a missing directory in play, since our globs don't
+    -- (currently) support disjunction, that will always mean there are no
+    -- matches. The no matches error in this case is strictly less informative
+    -- than the missing directory error, so sit on it.
+    suppressesNoMatchesWarning (GlobMatch _) = True
+    suppressesNoMatchesWarning (GlobWarnMultiDot _) = False
+    suppressesNoMatchesWarning (GlobMissingDirectory _) = True
+
     getWarning :: String -> FilePath -> GlobResult FilePath -> [PackageCheck]
     getWarning _ _ (GlobMatch _) =
       []

cabal-testsuite/PackageTests/Check/MissingGlobDirectory2/cabal.out

 # cabal check
-Warning: The package will not build sanely due to these errors:
-Warning: This package description follows version 2.4 of the Cabal specification. This tool only supports up to version 2.3.0.0.
 Warning: The following errors will cause portability problems on other environments:
-Warning: In 'data-files': the pattern 'non-existent-directory/**/*.dat' attempts to match files in the directory 'non-existent-directory', but there is no directory by that name.
+Warning: In 'data-files': the pattern 'non-existent-directory/*.dat' attempts to match files in the directory 'non-existent-directory', but there is no directory by that name.
 Warning: Hackage would reject this package.

cabal-testsuite/PackageTests/Check/MissingGlobDirectory2/pkg.cabal

-cabal-version: 2.4
+cabal-version: 2.2
 name: pkg
 version: 0
 data-files:
-  non-existent-directory/**/*.dat
+  non-existent-directory/*.dat
 category: example
 maintainer: none@example.com
 synopsis: synopsis

cabal-testsuite/PackageTests/Check/MultiDotGlob2.2/data/index.dat

+index.dat

cabal-testsuite/PackageTests/Check/MultiDotGlob2.2/doc/index.html

+index.html

cabal-testsuite/PackageTests/Check/MultiDotGlob2.2/src/index.js

+index.js

cabal-testsuite/PackageTests/Check/NoGlobMatches/cabal.out

+# cabal check
+Warning: The following errors will cause portability problems on other environments:
+Warning: In 'extra-doc-files': the pattern '*.html' does not match any files.
+Warning: Hackage would reject this package.

cabal-testsuite/PackageTests/Check/NoGlobMatches/cabal.test.hs

+import Test.Cabal.Prelude
+main = cabalTest $
+  fails $ cabal "check" []

cabal-testsuite/PackageTests/Check/NoGlobMatches/pkg.cabal

+cabal-version: 2.2
+name: pkg
+version: 0
+extra-doc-files:
+  *.html
+category: example
+maintainer: none@example.com
+synopsis: synopsis
+description: description
+license: BSD-3-Clause
+
+library
+  exposed-modules: Foo
+  default-language: Haskell2010