Merge pull request #9614 from haskell/test-help-prints-config-file

Test that the last line `--help` is the name of the config file

cabal-testsuite/PackageTests/Help/HelpPrintsConfigFile/help-prints-config-file.out

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+# cabal --help

cabal-testsuite/PackageTests/Help/HelpPrintsConfigFile/help-prints-config-file.test.hs

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+-- Andreas Abel, 2024-01-13
+--
+-- Ensure that the last line of the help text is the name of the config file.
+-- This invariant is used by clients such as the Haskell setup github action.
+-- See: https://github.com/haskell-actions/setup/pull/63
+
+import Distribution.Utils.String (trim)
+import Test.Cabal.Prelude
+
+main = cabalTest $ do
+  env <- getTestEnv
+  res <- cabal' "--help" []
+
+  -- The end of the help text should be something like:
+  --
+  -- > You can edit the cabal configuration file to set defaults:
+  -- >   <<HOME>>/.cabal/config
+  --
+  -- So trimming the last line will give us the name of the config file.
+  let configFile = trim . last . lines . resultOutput $ res
+
+  -- Verify that this is indeed the config file.
+  assertEqual "Last line of help text should be name of the config file"
+    (testUserCabalConfigFile env)
+    configFile