tar_SUITE: Work around limited pathname length on Windows

Ever since the test suites were converted to the common_test
convention, the tests for long names started to fail on Windows. The
reason is that those test cases depend on the current working
directory, and that the current working directory in common_test test
cases is usually set to a directory with a longer pathname than in
test_server test suites.

Since neither Erlang/OTP nor common_test provides a portable way
to create a temporary directory with a short name, we will have to
abuse priv_dir by going upwards from it. For further information,
see the comment in run_in_short_tempdir/2.

1 files changed, 47 insertions, 13 deletions

diff --git a/lib/stdlib/test/tar_SUITE.erl b/lib/stdlib/test/tar_SUITE.erl
index 48f58cd05d..9ad3936928 100644
--- a/lib/stdlib/test/tar_SUITE.erl
+++ b/lib/stdlib/test/tar_SUITE.erl
@@ -283,17 +283,16 @@ long_names(doc) ->
 long_names(Config) when is_list(Config) ->
     ?line DataDir = ?config(data_dir, Config),
     ?line Long = filename:join(DataDir, "long_names.tar"),
+    run_in_short_tempdir(Config,
+			 fun() -> do_long_names(Long) end).
 
+do_long_names(Long) ->
     %% Try table/2 and extract/2.
     ?line case erl_tar:table(Long, [verbose]) of
 	      {ok,List} when is_list(List) ->
 		  ?line io:format("~p\n", [List])
 	  end,
 
-
-    %% To avoid getting too long paths for Windows to handle, extract into
-    %% the current directory (which is the test_server directory). Its path
-    %% is quite a bit shorter than the path to priv_dir.
     ?line {ok,Cwd} = file:get_cwd(),
     ?line ok = erl_tar:extract(Long),
     ?line Base = filename:join([Cwd, "original_software", "written_by",
@@ -312,17 +311,16 @@ long_names(Config) when is_list(Config) ->
     ?line "Here"++_ = binary_to_list(First),
     ?line "And"++_ = binary_to_list(Second),
 
-    %% Clean up.
-    ?line delete_files([filename:join(Cwd, "original_software"),EmptyDir]),
-
     ok.
 
 create_long_names(doc) ->
     ["Creates a tar file from a deep directory structure (filenames are ",
      "longer than 100 characters)."];
 create_long_names(Config) when is_list(Config) ->
-    ?line PrivDir = ?config(priv_dir, Config),
-    ?line ok = file:set_cwd(PrivDir),
+    run_in_short_tempdir(Config, fun create_long_names/0).
+    
+create_long_names() ->
+    ?line {ok,Dir} = file:get_cwd(),
     Dirs = ["aslfjkshjkhliuf",
 	    "asdhjfehnbfsky",
 	    "sahajfskdfhsz",
@@ -334,7 +332,7 @@ create_long_names(Config) when is_list(Config) ->
     ?line AFile = filename:join(DeepDir, "a_file"),
     ?line Hello = "hello, world\n",
     ?line ok = file:write_file(AFile, Hello),
-    ?line TarName = filename:join(PrivDir,  "my_tar_with_long_names.tar"),
+    ?line TarName = filename:join(Dir,  "my_tar_with_long_names.tar"),
     ?line ok = erl_tar:create(TarName, [AFile]),
 
     %% Print contents.
@@ -347,9 +345,6 @@ create_long_names(Config) when is_list(Config) ->
     ?line {ok, Bin} = file:read_file(filename:join(ExtractDir, AFile)),
     ?line Hello = binary_to_list(Bin),
 
-    %% Clean up.
-    ?line delete_files([ExtractDir,TarName,hd(Dirs)]),
-
     ok.
 
 make_dirs([Dir|Rest], []) ->
@@ -734,3 +729,42 @@ delete_files([Item|Rest]) ->
     end,
     delete_files(Rest).
 
+%% Move to a temporary directory with as short name as possible and
+%% execute Fun. Remove the directory and any files in it afterwards.
+%% This is necessary because pathnames on Windows may be limited to
+%% 260 characters.
+run_in_short_tempdir(Config, Fun) ->
+    {ok,Cwd} = file:get_cwd(),
+    PrivDir0 = ?config(priv_dir, Config),
+
+    %% Normalize name to make sure that there is no slash at the end.
+    PrivDir = filename:absname(PrivDir0),
+
+    %% We need a base directory with a much shorter pathname than
+    %% priv_dir. We KNOW that priv_dir is located four levels below
+    %% the directory that common_test puts the ct_run.* directories
+    %% in. That fact is not documented, but an usually reliable source
+    %% assured me that the directory structure is unlikely to change
+    %% in future versions of common_test because of backward
+    %% compatibility (tools developed by users of common_test depend
+    %% on the current directory layout).
+    Base = lists:foldl(fun(_, D) ->
+			       filename:dirname(D)
+		       end, PrivDir, [1,2,3,4]),
+
+    Dir = make_temp_dir(Base, 0),
+    ok = file:set_cwd(Dir),
+    io:format("Running test in ~s\n", [Dir]),
+    try
+	Fun()
+    after
+	file:set_cwd(Cwd),
+	delete_files([Dir])
+    end.
+
+make_temp_dir(Base, I) ->
+    Name = filename:join(Base, integer_to_list(I, 36)),
+    case file:make_dir(Name) of
+	ok -> Name;
+	{error,eexist} -> make_temp_dir(Base, I+1)
+    end.