Make release issue on Windows

[saleyn]

Running rebar3 release on Windows with cygwin results in the following error:

$ ./rebar3 release
�[0;32m===> Verifying dependencies...
�[0mmake: Nothing to be done for 'all'.
�[0;32m===> Compiling mta
�[0m�[0;32m===> Compiling misc
�[0m�[0;32m===> Starting relx build process ...
�[0m�[0;32m===> Resolving OTP Applications from directories:
          d:/data/projects/mta/build/default/lib
          d:/data/projects/mta/apps
          c:/Program Files/erl7.1/lib
          d:/data/projects/mta/build/default/rel�[0m
�[0;35m===> Missing beam file elf_format <<"c:/Program Files/erl7.1/lib/hipe-3.13/ebin/elf_format.beam">>
�[0m�[0;32m===> Resolved mta-0.1
�[0m�[0;32m===> Dev mode enabled, release will be symlinked
�[0mCannot create a file when that file already exists.
Cannot create a file when that file already exists.
Cannot create a file when that file already exists.
Cannot create a file when that file already exists.
�[0;32m===> release successfully created!
�[0m�[0;31m===> Uncaught error in rebar_core. Run with DEBUG=1 to see stacktrace
�[0m�[0;32m===> When submitting a bug report, please include the output of `rebar3 report "your command"`
�[0m

I am not sure if the erl_format issue above is bogus.
The failing bit is in the overlay section which has:

{relx, [
    {overlay, [
        {link,     "apps/mta/etc/mta.test.config","{{output_dir}}/releases/{{rel_vsn}}/mta.test.config"}
...
]}.

The error below indicates that relx is failing with eperm though when creating the link by hand it works fine:
$ ln -s apps/mta/etc/mta.test.config build/default/rel/mta/releases/0.1/mta.test.config

�[0m�[0;31m===> Uncaught error in rebar_core. Run with DEBUG=1 to see stacktrace
�[0m�[0;36m===> Uncaught error: function_clause
�[0m�[0;36m===> Stack trace to the error location: [{rlx_prv_overlay,
                                                 format_error,
                                                 [{link_failed,
                                                   <<"d:/data/projects/mta/apps/mta/etc/mta.test.config">>,
                                                   <<"d:/data/projects/mta/build/default/rel/mta/releases/0.1/mta.test.config">>,
                                                   eperm}],
                                                 [{file,
                                                   "/home/travis/build/rebar/rebar3/_build/default/lib/relx/src/rlx_prv_overlay.erl"},
                                                  {line,72}]},
                                                {rlx_prv_overlay,
                                                 '-format_error/1-lc$^0/1-1-',
                                                 1,
                                                 [{file,
                                                   "/home/travis/build/rebar/rebar3/_build/default/lib/relx/src/rlx_prv_overlay.erl"},
                                                  {line,84}]},

Executing the same code in erlang by hand results in:

1> file:make_symlink("apps/mta/etc/mta.test.config", "build/default/rel/mta/releases/0.1/mta.test.config").
{error,eperm}

So, this works in cygwin's bash without issues, but fails when making file:make_symlink/2 call. Maybe a bug in this function that needs to be worked around by relx?

[ferd]

What's the version of rebar3 you're using? THat sounds like an older one from the broken color codes I see.

[saleyn]

My Windows Makefile is fetching it from "the official" pre-built location at amazonaws:

ifeq "$(REBAR)" ""
REBAR    := $(shell rm -f rebar3; wget -q https://s3.amazonaws.com/rebar3/rebar3; \
                            chmod a+x rebar3)$(wildcard ./rebar3)
endif

Here it is:

$ ./rebar3 version
rebar 3.0.0-beta.4+build.155.refa229a21 on Erlang/OTP 18 Erts 7.1

[ferd]

So the error has to do with:

[{link_failed, <<"d:/data/projects/mta/apps/mta/etc/mta.test.config">>,  <<"d:/data/projects/mta/build/default/rel/mta/releases/0.1/mta.test.config">>, eperm}],

Seems to indicate issues with permissions on either of the paths mentioned. Are all of these readable and/or writeable where required?

[saleyn]

Yes, as I've illustrated above, I am able to read/write to that location/file, and the link is created successfully when using ln -s in the cygwin's bash shell. The fact that this is Windows 10, I believe is irrelevant because it does support file linking (though mklink), and otherwise file:make_symlink/2 would have returned {error, enotsup} and it doesn't. This is likely the problem inside the file driver in erlang, though relx/rebar probably need to be aware of it and do some workaround.

Here's an example:

$ ln -s rebar3 rebar3.exe
$ ls -l rebar3*
-rwxrwxr-x+ 1 serge None 1129551 Feb  1 17:24 rebar3
lrwxrwxrwx  1 serge None       6 Feb  3 16:45 rebar3.exe -> rebar3
$ erl
Eshell V7.1  (abort with ^G)
1> file:make_symlink("rebar3", "rebar3.test.exe").
{error,eperm}

I also created a bug report here

[Taure]

Have you tried running it in Powershell?

I know I could do releases for some months ago with rebar3. Then I used Powershell and not cygwin.

[saleyn]

Apparently, as Lukas found out, this is a Windows issue that it only allows to create symlinks when a user has a special privilege granted. Somehow cygwin's ln works around the issue:

D:\data\projects\mta>mklink mta.iml.link mta.iml
You do not have sufficient privilege to perform this operation.

D:\data\projects\mta>ln -s mta.iml mta.iml.link

D:\data\projects\mta>ls -l mta.iml*
-rwxrwxr--+ 1 serge None 767 Feb  3 11:27 mta.iml
lrwxrwxrwx  1 serge None   7 Feb  4 08:25 mta.iml.link -> mta.iml

Not sure if it's a feasible solution, but maybe relx could check on Windows if ln is available and use it instead of file:make_symlink/2 or perhaps in case of a link command to check if the user has SeCreateSymbolicLinkPrivilege set and produce a more meaningful error.

[ferd]

Yeah in rebar3 we have to shell out to create symlinks in windows: https://github.com/rebar/rebar3/blob/master/src/rebar_file_utils.erl#L67-L112

I've marked this bug as related to a dependency if the problem only happens with relx.

[emtenet]

I have done some work in erlware/relx#472 in relation to creating symlinks on Windows that may help with this issue. I did not look or test its usage for overlays.