stdlib: Fix a Dets bug where files were deleted

Instead of deleting the small file when opening it with
dets:open_file/2 an error message is returned, mimicking the behaviour
when the file is bigger.

open_file/1 has been modified to return the same error message when
the file is small as when the file is bigger.

Thanks to Hakan Mattson for reporting this bug.

2 files changed, 37 insertions, 26 deletions

diff --git a/lib/stdlib/src/dets.erl b/lib/stdlib/src/dets.erl
index 8c5c86f3b9..c32da1624f 100644
--- a/lib/stdlib/src/dets.erl
+++ b/lib/stdlib/src/dets.erl
@@ -2114,6 +2114,8 @@ test_bchunk_format(Head, Term) ->
 
 do_open_file([Fname, Verbose], Parent, Server, Ref) ->
     case catch fopen2(Fname, Ref) of
+	{error, {tooshort, _}} ->
+            err({error, {not_a_dets_file, Fname}});
 	{error, _Reason} = Error ->
 	    err(Error);
 	{ok, Head} ->
@@ -2127,11 +2129,10 @@ do_open_file([Fname, Verbose], Parent, Server, Ref) ->
 	       [Bad]),
 	    {error, {dets_bug, Fname, Bad}}
     end;
-do_open_file([Tab, OpenArgs, Verb], Parent, Server, Ref) ->
+do_open_file([Tab, OpenArgs, Verb], Parent, Server, _Ref) ->
     case catch fopen3(Tab, OpenArgs) of
 	{error, {tooshort, _}} ->
-	    _ = file:delete(OpenArgs#open_args.file),
-	    do_open_file([Tab, OpenArgs, Verb], Parent, Server, Ref);
+            err({error, {not_a_dets_file, OpenArgs#open_args.file}});
 	{error, _Reason} = Error ->
 	    err(Error);
 	{ok, Head} ->
@@ -2487,7 +2488,6 @@ fopen2(Fname, Tab) ->
 	{ok, _} ->
 	    Acc = read_write,
 	    Ram = false, 
-	    %% Fd is not always closed upon error, but exit is soon called.
 	    {ok, Fd, FH} = read_file_header(Fname, Acc, Ram),
             Mod = FH#fileheader.mod,
             Do = case Mod:check_file_header(FH, Fd) of
@@ -2543,7 +2543,6 @@ fopen_existing_file(Tab, OpenArgs) ->
                ram_file = Ram, delayed_write = CacheSz, auto_save =
                Auto, access = Acc, version = Version, debug = Debug} =
         OpenArgs,
-    %% Fd is not always closed upon error, but exit is soon called.
     {ok, Fd, FH} = read_file_header(Fname, Acc, Ram),
     V9 = (Version =:= 9) or (Version =:= default),
     MinF = (MinSlots =:= default) or (MinSlots =:= FH#fileheader.min_no_slots),
diff --git a/lib/stdlib/test/dets_SUITE.erl b/lib/stdlib/test/dets_SUITE.erl
index 0f6b76a629..00a5da42ad 100644
--- a/lib/stdlib/test/dets_SUITE.erl
+++ b/lib/stdlib/test/dets_SUITE.erl
@@ -772,9 +772,9 @@ open_1(Config, V) ->
     crash(Fname, TypePos),
     {error, {invalid_type_code,Fname}} = dets:open_file(Fname),
     truncate(Fname, HeadSize - 10),
-    {error, {tooshort,Fname}} = dets:open_file(Fname),
-    {ok, TabRef} = dets:open_file(TabRef, [{file,Fname},{version,V}]),
-    ok = dets:close(TabRef),
+    {error,{not_a_dets_file,Fname}} = dets:open_file(Fname),
+    {error,{not_a_dets_file,Fname}} =
+        dets:open_file(TabRef, [{file,Fname},{version,V}]),
     file:delete(Fname),
 
     {error,{file_error,{foo,bar},_}} = dets:is_dets_file({foo,bar}),
@@ -967,10 +967,12 @@ fast_init_table(Config) ->
     {'EXIT', _} =
 	(catch dets:init_table(TabRef, fun(foo) -> bar end, {format,bchunk})),
     dets:close(TabRef),
+    file:delete(Fname),
     {ok, _} = dets:open_file(TabRef, Args),
     {'EXIT', _} = (catch dets:init_table(TabRef, fun() -> foo end,
 					       {format,bchunk})),
     dets:close(TabRef),
+    file:delete(Fname),
     {ok, _} = dets:open_file(TabRef, Args),
     {'EXIT', {badarg, _}} =
 	(catch dets:init_table(TabRef, nofun, {format,bchunk})),
@@ -979,10 +981,12 @@ fast_init_table(Config) ->
     away = (catch dets:init_table(TabRef, fun(_) -> throw(away) end,
 					{format,bchunk})),
     dets:close(TabRef),
+    file:delete(Fname),
     {ok, _} = dets:open_file(TabRef, Args),
     {error, {init_fun, fopp}} =
 	dets:init_table(TabRef, fun(read) -> fopp end, {format,bchunk}),
     dets:close(TabRef),
+    file:delete(Fname),
     {ok, _} = dets:open_file(TabRef, Args),
     dets:safe_fixtable(TabRef, true),
     {error, {fixed_table, TabRef}} =
@@ -1389,23 +1393,6 @@ repair(Config, V) ->
     {ok, TabRef} = dets:open_file(TabRef, [{file,Fname},{version,V}]),
     ok = ins(TabRef, 100),
     ok = dets:close(TabRef),
-    truncate(Fname, HeadSize - 10),
-    %% a new file is created ('tooshort')
-    {ok, TabRef} = dets:open_file(TabRef,
-                                  [{file,Fname},{version,V},
-                                   {min_no_slots,1000},
-                                   {max_no_slots,1000000}]),
-    case dets:info(TabRef, no_slots) of
-	undefined -> ok;
-	{Min1,Slot1,Max1} ->
-	    true = Min1 =< Slot1, true = Slot1 =< Max1,
-	    true = 1000 < Min1, true = 1000+256 > Min1,
-	    true = 1000000 < Max1, true = (1 bsl 20)+256 > Max1
-    end,
-    0 = dets:info(TabRef, size),
-    no_keys_test(TabRef),
-    _ = histogram(TabRef, silent),
-    ok = dets:close(TabRef),
     file:delete(Fname),
 
     %% version bump (v8)
@@ -3925,6 +3912,7 @@ otp_11709(doc) ->
 otp_11709(suite) ->
     [];
 otp_11709(Config) when is_list(Config) ->
+    Short = <<"foo">>,
     Long = <<"a sufficiently long text">>,
 
     %% Bug: leaking file descriptor
@@ -3934,7 +3922,31 @@ otp_11709(Config) when is_list(Config) ->
     false = dets:is_dets_file(File),
     check_pps(P0),
 
-    file:delete(File),
+    %% Bug: deleting file
+    Args = [[{access, A}, {repair, R}] ||
+               A <- [read, read_write],
+               R <- [true, false, force]],
+    Fun1 = fun(S, As) ->
+                   P1 = pps(),
+                   ok = file:write_file(File, S),
+                   {error,{not_a_dets_file,File}} = dets:open_file(File, As),
+                   {ok, S} = file:read_file(File),
+                   check_pps(P1)
+           end,
+    Fun2 = fun(S) ->
+                   _ = [Fun1(S, As) || As <- Args],
+                   ok
+           end,
+    ok = Fun2(Long),  % no change here
+    ok = Fun2(Short), % mimic the behaviour for longer files
+
+    %% open_file/1
+    ok = file:write_file(File, Long),
+    {error,{not_a_dets_file,File}} = dets:open_file(File), % no change
+    ok = file:write_file(File, Short),
+    {error,{not_a_dets_file,File}} = dets:open_file(File), % mimic
+
+    _ = file:delete(File),
     ok.
 
 %%