[commit: ghc] master: Improve error message for flags with missing required arguments (#12625) (ff06176)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/ff06176b87078ce56cc7b6b3405a029ef3d0046f/ghc

>---------------------------------------------------------------

commit ff06176b87078ce56cc7b6b3405a029ef3d0046f
Author: roland <rsx at bluewin.ch>
Date:   Mon Aug 6 12:50:38 2018 -0400

    Improve error message for flags with missing required arguments (#12625)
    
    Test Plan: make TEST=T12625
    
    Reviewers: jstolarek, austin, bgamari
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie, carter
    
    GHC Trac Issues: #12625
    
    Differential Revision: https://phabricator.haskell.org/D5030


>---------------------------------------------------------------

ff06176b87078ce56cc7b6b3405a029ef3d0046f
 compiler/main/CmdLineParser.hs                         | 6 ++++--
 testsuite/tests/driver/T12625.hs                       | 2 ++
 testsuite/tests/driver/{T3364.stderr => T12625.stderr} | 2 +-
 testsuite/tests/driver/all.T                           | 2 ++
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/compiler/main/CmdLineParser.hs b/compiler/main/CmdLineParser.hs
index 49fbd8f..c876f58 100644
--- a/compiler/main/CmdLineParser.hs
+++ b/compiler/main/CmdLineParser.hs
@@ -242,8 +242,9 @@ processOneArg opt_kind rest arg args
                         []               -> missingArgErr dash_arg
                         (L _ arg1:args1) -> Right (f arg1, args1)
 
+        -- See Trac #12625
         Prefix f | notNull rest_no_eq -> Right (f rest_no_eq, args)
-                 | otherwise          -> unknownFlagErr dash_arg
+                 | otherwise          -> missingArgErr  dash_arg
 
         PrefixPred _ f | notNull rest_no_eq -> Right (f rest_no_eq, args)
                        | otherwise          -> unknownFlagErr dash_arg
@@ -281,7 +282,8 @@ arg_ok :: OptKind t -> [Char] -> String -> Bool
 arg_ok (NoArg           _)  rest _   = null rest
 arg_ok (HasArg          _)  _    _   = True
 arg_ok (SepArg          _)  rest _   = null rest
-arg_ok (Prefix          _)  rest _   = notNull rest
+arg_ok (Prefix          _)  _    _   = True -- Missing argument checked for in processOneArg t
+                                            -- to improve error message (Trac #12625)
 arg_ok (PrefixPred p    _)  rest _   = notNull rest && p (dropEq rest)
 arg_ok (OptIntSuffix    _)  _    _   = True
 arg_ok (IntSuffix       _)  _    _   = True
diff --git a/testsuite/tests/driver/T12625.hs b/testsuite/tests/driver/T12625.hs
new file mode 100644
index 0000000..b34b914
--- /dev/null
+++ b/testsuite/tests/driver/T12625.hs
@@ -0,0 +1,2 @@
+main :: IO()
+main = putStrLn "T12625"
diff --git a/testsuite/tests/driver/T3364.stderr b/testsuite/tests/driver/T12625.stderr
similarity index 50%
copy from testsuite/tests/driver/T3364.stderr
copy to testsuite/tests/driver/T12625.stderr
index 852893f..a171dbd 100644
--- a/testsuite/tests/driver/T3364.stderr
+++ b/testsuite/tests/driver/T12625.stderr
@@ -1,2 +1,2 @@
-ghc: on the commandline: missing argument for flag: -H
+ghc: on the commandline: missing argument for flag: -I
 Usage: For basic information, try the `--help' option.
diff --git a/testsuite/tests/driver/all.T b/testsuite/tests/driver/all.T
index 6397598..07dc3bf 100644
--- a/testsuite/tests/driver/all.T
+++ b/testsuite/tests/driver/all.T
@@ -264,6 +264,8 @@ test('T12192', normal, run_command, ['mkdir foo && (cd foo && {compiler} -v0 ../
 
 test('T10923', [], run_command, ['$MAKE -s --no-print-directory T10923'])
 
+test('T12625', normal, compile_fail, ['-I'])
+
 test('T12752pass', normal, compile, ['-DSHOULD_PASS=1 -Wcpp-undef'])
 
 test('T12955', normal, run_command, ['$MAKE -s --no-print-directory T12955'])