compiler application needed for install_upgrade.escript?

[benbro]

Is there a way to make install_upgrade.escript work without adding the compiler application (3MB) to the release?
Might be related: #589

When I'm calling bin/mytest upgrade 0.2.0 on a target server I'm getting an error:

escript: Internal error: undef
[{compile,forms,
  [[{attribute,{3,1},file,{"mytest/bin/install_upgrade.escript",3}},
  ...

It works after I add the compiler application to the release in rebar.config:

{relx, [
    {release, { mytest, "0.2.0" },
        [mytest,
         sasl,
         compiler]},
    {dev_mode, false},
    {include_erts, true},
    {include_src, false},
    {sys_config, "./config/sys.config"},
    {vm_args, "./config/vm.args"}
]}

[ferd]

Ah I'm surprised by it, but it turns out that over time the Erlang distribution changed how escripts work. It used to be we needed to pass -mode(compile). for the escript to be compiled, but this changed and now we need to pass in -mode(interpret). starting with OTP-27. We'll need to modify all escripts in https://github.com/erlware/relx/tree/main/priv/templates to have -mode(interpret). in order to be safe on newer Erlang versions.

[ferd]

#941 should fix it