From 6f5c79240554dbb5caaafcb9124e8917e62c980d Mon Sep 17 00:00:00 2001
From: Hans Bolinder <hasse@erlang.org>
Date: Mon, 6 Feb 2017 15:45:45 +0100
Subject: stdlib: Improve Erlang shell's tab-completion of long names

---
 lib/stdlib/src/edlin_expand.erl | 95 +++++++++++++++++++++++++++--------------
 1 file changed, 64 insertions(+), 31 deletions(-)

(limited to 'lib/stdlib/src')

diff --git a/lib/stdlib/src/edlin_expand.erl b/lib/stdlib/src/edlin_expand.erl
index 5f821caef0..a1a97af4c5 100644
--- a/lib/stdlib/src/edlin_expand.erl
+++ b/lib/stdlib/src/edlin_expand.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2005-2016. All Rights Reserved.
+%% Copyright Ericsson AB 2005-2017. All Rights Reserved.
 %%
 %% Licensed under the Apache License, Version 2.0 (the "License");
 %% you may not use this file except in compliance with the License.
@@ -101,44 +101,77 @@ match(Prefix, Alts, Extra0) ->
 
 %% Return the list of names L in multiple columns.
 format_matches(L) ->
-    S = format_col(lists:sort(L), []),
+    {S1, Dots} = format_col(lists:sort(L), []),
+    S = case Dots of
+            true ->
+                {_, Prefix} = longest_common_head(vals(L)),
+                PrefixLen = length(Prefix),
+                case PrefixLen =< 3 of
+                    true -> S1; % Do not replace the prefix with "...".
+                    false ->
+                        LeadingDotsL = leading_dots(L, PrefixLen),
+                        {S2, _} = format_col(lists:sort(LeadingDotsL), []),
+                        S2
+                end;
+            false -> S1
+        end,
     ["\n" | S].
 
 format_col([], _) -> [];
-format_col(L, Acc) -> format_col(L, field_width(L), 0, Acc).
-
-format_col(X, Width, Len, Acc) when Width + Len > 79 ->
-    format_col(X, Width, 0, ["\n" | Acc]);
-format_col([A|T], Width, Len, Acc0) ->
-    H = case A of
- 	    %% If it's a tuple {string(), integer()}, we assume it's an
- 	    %% arity, and meant to be printed.
-	    {H0, I} when is_integer(I) ->
-		H0 ++ "/" ++ integer_to_list(I);
-	    {H1, _} -> H1;
- 	    H2 -> H2
- 	end,
-    Acc = [io_lib:format("~-*ts", [Width,H]) | Acc0],
-    format_col(T, Width, Len+Width, Acc);
-format_col([], _, _, Acc) ->
-    lists:reverse(Acc, "\n").
-
-field_width(L) -> field_width(L, 0).
-
-field_width([{H,_}|T], W) ->
+format_col(L, Acc) ->
+    LL = 79,
+    format_col(L, field_width(L, LL), 0, Acc, LL, false).
+
+format_col(X, Width, Len, Acc, LL, Dots) when Width + Len > LL ->
+    format_col(X, Width, 0, ["\n" | Acc], LL, Dots);
+format_col([A|T], Width, Len, Acc0, LL, Dots) ->
+    {H0, R} = format_val(A),
+    Hmax = LL - length(R),
+    {H, NewDots} =
+        case length(H0) > Hmax of
+            true -> {io_lib:format("~-*ts", [Hmax - 3, H0]) ++ "...", true};
+            false -> {H0, Dots}
+        end,
+    Acc = [io_lib:format("~-*ts", [Width, H ++ R]) | Acc0],
+    format_col(T, Width, Len+Width, Acc, LL, NewDots);
+format_col([], _, _, Acc, _LL, Dots) ->
+    {lists:reverse(Acc, "\n"), Dots}.
+
+format_val({H, I}) when is_integer(I) ->
+    %% If it's a tuple {string(), integer()}, we assume it's an
+    %% arity, and meant to be printed.
+    {H, "/" ++ integer_to_list(I)};
+format_val({H, _}) ->
+    {H, ""};
+format_val(H) ->
+    {H, ""}.
+
+field_width(L, LL) -> field_width(L, 0, LL).
+
+field_width([{H,_}|T], W, LL) ->
     case length(H) of
- 	L when L > W -> field_width(T, L);
- 	_ -> field_width(T, W)
+        L when L > W -> field_width(T, L, LL);
+        _ -> field_width(T, W, LL)
     end;
-field_width([H|T], W) ->
+field_width([H|T], W, LL) ->
     case length(H) of
- 	L when L > W -> field_width(T, L);
- 	_ -> field_width(T, W)
+        L when L > W -> field_width(T, L, LL);
+        _ -> field_width(T, W, LL)
     end;
-field_width([], W) when W < 40 ->
+field_width([], W, LL) when W < LL - 3 ->
     W + 4;
-field_width([], _) ->
-    40.
+field_width([], _, LL) ->
+    LL.
+
+vals([]) -> [];
+vals([{S, _}|L]) -> [S|vals(L)];
+vals([S|L]) -> [S|vals(L)].
+
+leading_dots([], _Len) -> [];
+leading_dots([{H, I}|L], Len) ->
+    [{"..." ++ nthtail(Len, H), I}|leading_dots(L, Len)];
+leading_dots([H|L], Len) ->
+    ["..." ++ nthtail(Len, H)|leading_dots(L, Len)].
 
 longest_common_head([]) ->
     no;
-- 
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