Doesn't work on macOS

[eilvelia]

Executing opam switch create . ocaml-base-compiler.4.10.1 on macOS 10.14.6 fails with:

# fatal exception Failure("Command 'tar -cf /Users/user/test/_opam/.opam-switch/opam-bin/ocaml-base-compiler-bin.tar.gz.tmp --mtime=2020/07/13 --group=user:1000 --owner=user:1000 --transform s|^|prefix/|S bin/ocaml bin/ocaml-instr-graph bin/ocaml-instr-report bin/ocamlc bin/ocamlc.byte bin/ocamlc.opt bin/ocamlcmt bin/ocamlcp bin/ocamlcp.byte bin/ocamlcp.opt bin/ocamldebug bin/ocamldep bin/oca[...]
# Raised at Stdlib.failwith in file "stdlib.ml", line 29, characters 17-33
# Called from Opam_bin_lib__Misc.tar_zcf in file "src/opam_bin_lib/misc.ml", line 121, characters 6-45
# Called from Opam_bin_lib__CommandPostInstall.commit in file "src/opam_bin_lib/commandPostInstall.ml", line 283, characters 12-69
# Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 25, characters 19-24
# Called from Cmdliner.Term.run in file "cmdliner.ml", line 117, characters 32-39
# Called from Cmdliner.Term.term_eval in file "cmdliner.ml", line 147, characters 18-36
# Called from Cmdliner.Term.eval_choice in file "cmdliner.ml", line 265, characters 22-48
# Called from Ezcmd.main_with_subcommands in file "src/ezcmd.ml", line 194, characters 8-54
# Called from Opam_bin_lib__Main.main in file "src/opam_bin_lib/main.ml", line 45, characters 6-191
#

BSD tar doesn't have options like group, owner, etc. That seems to be the reason.

Update: opam-bin seems to use other options that don't exist on BSD, like -T from cp. These options aren't part of the POSIX standard.

[lefessan]

It looks like gnu-tar is available in brew and called gtar, I will modify the code to use it on Mac OS.
Any idea of what the equivalent is for cp -T on Mac OS ?

[eilvelia]

Looks like BSD cp has similar behaviour if the source ends with /

If the source_file ends in a /, the contents of the directory are copied rather than the directory itself

$ tree
.
├── test1
│   ├── file1
│   └── file2
└── test2
$ cp -a test1/ test2
$ tree
.
├── test1
│   ├── file1
│   └── file2
└── test2
    ├── file1
    └── file2

GNU cp, though, treats test1 and test1/ the same.

[mattjbray]

A workaround is to install gnu-tar and coreutils:

brew install coreutils gnu-tar

Then add the gnubin directories to your path (as directed by the brew caveats):

export PATH="/usr/local/opt/coreutils/libexec/gnubin:/usr/local/opt/gnu-tar/libexec/gnubin:$PATH"

Then opam-bin will find the GNU versions of tar and ls.

[yawaramin]

I'm getting I guess the same error, with a little more output:

### output ###
# tar: Option --mtime=2020/07/13 is not supported
# Usage:
#   List:    tar -tf <archive-filename>
#   Extract: tar -xf <archive-filename>
#   Create:  tar -cf <archive-filename> [filenames...]
#   Help:    tar --help
# fatal exception Failure("Command 'tar -cf /Users/me/src/github.com/yawaramin/odoc/_opam/.opam-switch/opam-bin/ocaml-base-compiler-bin.tar.gz.tmp --mtime=2020/07/13 --group=user:1000 --owner=user:1000 --transform s|^|prefix/|S bin/ocaml bin/ocamlc bin/ocamlc.byte bin/ocamlc.opt bin/ocamlcmt bin/ocamlcp bin/ocamlcp.byte bin/ocamlcp.opt bin/ocamldebug bin/ocamldep bin/ocamldep.byte [...]

On macOS without GNU coreutils. Any way we can make this work without the coreutils workaround? I would love to use opam-bin but can't if it can't create switches or if I need duplicate copies of Unix tools (which also make a Windows port more difficult).