Select just the first alias for each command for bash completions.

Author: HuwCampbell

src/Options/Applicative/BashCompletion.hs

@@ -17,10 +17,11 @@ import Prelude
 #if !defined(__MHS__)
 import Data.Foldable ( asum )
 #endif
+
+import qualified Data.Foldable as Foldable
 import Data.List ( isPrefixOf )
 import Data.List.NonEmpty (NonEmpty)
-import qualified Data.List.NonEmpty as NE
-import Data.Maybe ( fromMaybe, listToMaybe )
+import Data.Maybe ( fromMaybe, listToMaybe, mapMaybe )
 
 import Options.Applicative.Builder
 import Options.Applicative.Common
@@ -159,12 +160,20 @@ bashCompletionQuery pinfo pprefs richness ws i _ = case runCompletion compl ppre
     --
     -- and the user types 'r', we should return
     --
-    --   [(retry, p1), (run, p2), (r, p2)]
+    --   [(retry, p1), (run, p2)]
+    --
+    -- If the first entry (command name) is the canonical one, we should
+    -- favour it in completions, as if we were to provide all options there
+    -- would be a good chance we'd be forcing the user to tab through and
+    -- disambiguate between functionally identical options.
+    --
+    -- In zsh and fish we also provide the help doc in the completions, which
+    -- we don't want to repeat a whole bunch of times.
     filter_completions :: [(NonEmpty String, ParserInfo a)] -> [(String, ParserInfo a)]
     filter_completions =
-      let matchZip :: (NonEmpty String, b) -> [(String, b)]
-          matchZip (aliases, painfo) = (\x -> (x, painfo)) <$> NE.filter is_completion aliases
-      in (>>= matchZip)
+      let findAlias :: (NonEmpty String, b) -> Maybe (String, b)
+          findAlias (aliases, painfo) = (\x -> (x, painfo)) <$> Foldable.find is_completion aliases
+      in mapMaybe findAlias
 
     -- We only want to show a single line in the completion results description.
     -- If there was a line break, it would come across as a different completion

tests/test.hs

@@ -187,16 +187,7 @@ prop_cmd_aliases_completion = once . ioProperty $
     Success val -> return $ counterexample ("unexpected result " ++ show val) failed
   where
     expected =
-      [ "goodbye"
-      , "hello"
-      , "hi"
-      , "au-revoir"
-      , "adieu"
-      , "ciao"
-      , "bonjour"
-      , "aux"
-      , "health"
-      ]
+      ["goodbye","hello","au-revoir","bonjour","aux","health"]
 
 prop_cmd_aliases_completion_alias1 :: Property
 prop_cmd_aliases_completion_alias1 = once . ioProperty $
@@ -222,10 +213,7 @@ prop_cmd_aliases_completion_alias2 = once . ioProperty $
   in assertCompletions result (=== expected)
   where
     expected =
-      [ "au-revoir"
-      , "adieu"
-      , "aux"
-      ]
+      ["au-revoir","aux"]
 
 prop_cmd_aliases_completion_alias3 :: Property
 prop_cmd_aliases_completion_alias3 = once . ioProperty $
@@ -263,13 +251,7 @@ prop_cmd_aliases_dupes_completion = once . ioProperty $
   in assertCompletions result (=== expected)
   where
     expected =
-      [ "goodbye"
-      , "g"
-      , "h"
-      , "hello"
-      , "hi"
-      , "h"
-      ]
+      ["goodbye","hello"]
 
 prop_cmd_aliases_dupes_completion_alias1 :: Property
 prop_cmd_aliases_dupes_completion_alias1 = once . ioProperty $
@@ -281,11 +263,7 @@ prop_cmd_aliases_dupes_completion_alias1 = once . ioProperty $
   in assertCompletions result (=== expected)
   where
     expected =
-      [ "h"
-      , "hello"
-      , "hi"
-      , "h"
-      ]
+      ["h","hello"]
 
 prop_alts :: Property
 prop_alts = once $