Emit a warning when -g was not passed (#268)

Fixes #268.

src/Main.lhs

@@ -25,7 +25,7 @@ Path settings auto-generated by Cabal:
 > import Happy.Tabular.Info (genInfoFile)
 
 > import System.Console.GetOpt
-> import Control.Monad ( liftM, when )
+> import Control.Monad ( liftM, when, unless )
 > import System.Environment
 > import System.Exit (exitWith, ExitCode(..))
 > import Data.Char
@@ -62,6 +62,11 @@ Read and parse the CLI arguments.
 >  where
 >    runParserGen cli fl_name = do
 
+If no -g flag has been passed, show a warning.
+
+>       unless (OptGhcTarget `elem` cli) $
+>           hPutStrLn stderr "Warning: With happy 2.0, the --ghc flag has become non-optional. To suppress this warning, pass the --ghc flag."
+
 Open the file.
 
 >       fl <- readFile fl_name

tests/Makefile

@@ -44,16 +44,16 @@ ERROR_TESTS = error001.y
 
 # NOTE: `cabal` will set the `happy_datadir` env-var accordingly before invoking the test-suite
 #TEST_HAPPY_OPTS = --strict --template=..
-TEST_HAPPY_OPTS = --strict
+TEST_HAPPY_OPTS = --strict -g
 
 %.n.hs : %.y
 	$(HAPPY) $(TEST_HAPPY_OPTS) $< -o $@
 
 %.n.hs : %.ly
-	$(HAPPY) $(TEST_HAPPY_OPTS) -c $< -o $@
+	$(HAPPY) $(TEST_HAPPY_OPTS) $< -o $@
 
 %.c.hs : %.y
-	$(HAPPY) $(TEST_HAPPY_OPTS) $< -o $@
+	$(HAPPY) $(TEST_HAPPY_OPTS) -c $< -o $@
 
 %.c.hs : %.ly
 	$(HAPPY) $(TEST_HAPPY_OPTS) -c $< -o $@
@@ -80,7 +80,7 @@ path.run : # simply a test to output the path of the built happy executable, use
 
 check.%.y : %.y
 	@echo "--> Checking $<..."
-	$(HAPPY) $(TEST_HAPPY_OPTS) $< 1>$*.run.stdout 2>$*.run.stderr || true
+	$(HAPPY) $(TEST_HAPPY_OPTS) -g $< 1>$*.run.stdout 2>$*.run.stderr || true
 	sed -i '/^Up to date$$/d' $*.run.stdout $*.run.stderr
 	@diff -u --ignore-all-space $*.stdout $*.run.stdout
 	@diff -u --ignore-all-space $*.stderr $*.run.stderr