Fix handling of ~and_exit parameter when running via CLI functor

[craigfe]

Fix #270.

The logic that processes Cmdliner results was incorrect (again), resulting in failure to respect ~and_exit:false when an exception is raised by the user code. In future, we should consolidate this parameter handling logic in one place (i.e. in Core when necessary) to avoid such bugs.

Also cleans up the bad.ml example slightly, which was a bit hard to read before.

[samoht]

Do you know why do we need ppx_string? In any case, it seems there is a broken constraint.

#16 741.1 #=== ERROR while compiling ppx_string.v0.14.0 =================================#
#16 741.1 # context              2.0.7 | linux/x86_64 | ocaml-base-compiler.4.10.1 | file:///home/opam/opam-repository
#16 741.1 # path                 ~/.opam/4.10/.opam-switch/build/ppx_string.v0.14.0
#16 741.1 # command              ~/.opam/4.10/bin/dune build -p ppx_string -j 31
#16 741.1 # exit-code            1
#16 741.1 # env-file             ~/.opam/log/ppx_string-1-6dcac4.env
#16 741.1 # output-file          ~/.opam/log/ppx_string-1-6dcac4.out
#16 741.1 ### output ###
#16 741.1 #       ocamlc src/.ppx_string.objs/byte/ppx_string.{cmo,cmt} (exit 2)
#16 741.1 # (cd _build/default && /home/opam/.opam/4.10/bin/ocamlc.opt -w -40 -g -bin-annot -I src/.ppx_string.objs/byte -I /home/opam/.opam/4.10/lib/base -I /home/opam/.opam/4.10/lib/base/base_internalhash_types -I /home/opam/.opam/4.10/lib/base/caml -I /home/opam/.opam/4.10/lib/base/shadow_stdlib -I /home/opam/.opam/4.10/lib/ocaml-compiler-libs/common -I /home/opam/.opam/4.10/lib/ocaml-compiler-libs/shadow -I /home/opam/.opam/4.10/lib/ocaml-migrate-parsetree -I /home/opam/.opam/4.10/lib/ocaml/compiler-libs -I /home/opam/.opam/4.10/lib/ppx_compare/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_derivers -I /home/opam/.opam/4.10/lib/ppx_enumerate/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_hash/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.10/lib/ppxlib -I /home/opam/.opam/4.10/lib/ppxlib/ast -I /home/opam/.opam/4.10/lib/ppxlib/print_diff -I /home/opam/.opam/4.10/lib/ppxlib/stdppx -I /home/opam/.opam/4.10/lib/ppxlib/traverse_builtins -I /home/opam/.opam/4.10/lib/sexplib0 -I /home/opam/.opam/4.10/lib/stdlib-shims -intf-suffix .ml -no-alias-deps -o src/.ppx_string.objs/byte/ppx_string.cmo -c -impl src/ppx_string.pp.ml)
#16 741.1 # File "src/ppx_string.ml", line 98, characters 6-32:
#16 741.1 # 98 |       Stdio.In_channel.with_file loc.loc_start.pos_fname ~f:(fun ic ->
#16 741.1 #            ^^^^^^^^^^^^^^^^^^^^^^^^^^
#16 741.1 # Error: Unbound module Stdio
#16 741.1 # Hint: Did you mean Stdlib?
#16 741.1 #     ocamlopt src/.ppx_string.objs/native/ppx_string.{cmx,o} (exit 2)
#16 741.1 # (cd _build/default && /home/opam/.opam/4.10/bin/ocamlopt.opt -w -40 -g -I src/.ppx_string.objs/byte -I src/.ppx_string.objs/native -I /home/opam/.opam/4.10/lib/base -I /home/opam/.opam/4.10/lib/base/base_internalhash_types -I /home/opam/.opam/4.10/lib/base/caml -I /home/opam/.opam/4.10/lib/base/shadow_stdlib -I /home/opam/.opam/4.10/lib/ocaml-compiler-libs/common -I /home/opam/.opam/4.10/lib/ocaml-compiler-libs/shadow -I /home/opam/.opam/4.10/lib/ocaml-migrate-parsetree -I /home/opam/.opam/4.10/lib/ocaml/compiler-libs -I /home/opam/.opam/4.10/lib/ppx_compare/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_derivers -I /home/opam/.opam/4.10/lib/ppx_enumerate/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_hash/runtime-lib -I /home/opam/.opam/4.10/lib/ppx_sexp_conv/runtime-lib -I /home/opam/.opam/4.10/lib/ppxlib -I /home/opam/.opam/4.10/lib/ppxlib/ast -I /home/opam/.opam/4.10/lib/ppxlib/print_diff -I /home/opam/.opam/4.10/lib/ppxlib/stdppx -I /home/opam/.opam/4.10/lib/ppxlib/traverse_builtins -I /home/opam/.opam/4.10/lib/sexplib0 -I /home/opam/.opam/4.10/lib/stdlib-shims -intf-suffix .ml -no-alias-deps -o src/.ppx_string.objs/native/ppx_string.cmx -c -impl src/ppx_string.pp.ml)
#16 741.1 # File "src/ppx_string.ml", line 98, characters 6-32:
#16 741.1 # 98 |       Stdio.In_channel.with_file loc.loc_start.pos_fname ~f:(fun ic ->

[craigfe]

Do you know why do we need ppx_string?

Yes: alcotest-async → core_kernel → ppx_jane → ppx_string

Hopefully it'll be patched soon. Until then, we'll have to use Travis.

[craigfe]

Now rebased over #274.