Interpreter: Apply shell expansion in ldflags

[mdwagner]

#12061

I tried following what the compiler does, and saw Windows does this too (https://github.com/crystal-lang/crystal/blob/master/src/compiler/crystal/compiler.cr#L346), so I think this will work now.

However, I get this error on an Intel Mac when trying to run the test file from the issue:

But it seems that might just be an issue with BigSur and/or openssl? The spec seems to properly expand now and that passed locally, so maybe its just an issue with my machine?

UPDATE: I was able to make a better spec that properly tests the original issue. Although, I think the issue I was experiencing above is specific to my machine.

[straight-shoota]

Suggested change

	lib_flags = lib_flags.gsub(/`(.*?)`/) { `#{$1}` }
	# Execute and expand `subcommands`.
	lib_flags = lib_flags.gsub(/`(.*?)`/) { `#{$1}` }

[straight-shoota]

This spec tests the changed behaviour only coincidentally. It depends on the bindings and link flags for LibSSL.
It would be better to have a dedicated test specifically for this command expansion in interpreter/lib_spec.cr.
Let me know if you need help with that.

[mdwagner]

Ah ok. I had the test originally in lib_spec, but thought it was a little different. I'll add it back.
Can you elaborate a little bit on how I can test the command is expanding? I'm just wondering if its a simple as checking if echo ... worked, or you had something else in mind?

[straight-shoota]

Yes, I think a simple example of a lib type with bindings specified via shell expansion in ldflags should be fine. If that links / executes, we can be sure that it works.
We're already using a custom libsum in lib_spec for testing variadic arguments. This lib should be available and the symbols are known and consistent. We can probably just derive from one of the existing samples, replacing -lsum with "-l`echo sum`" (for example).

Optionally adding trivial function to the lib because we don't need variadics here; but it's probably fine to just use an existing symbol if you like.

[cyangle]

This is great! I can use the interpreter to debug a Kemal hello world server now.

[development] Kemal is ready to lead at http://0.0.0.0:3000
From: bin/server.cr:7:3 <Program>#->:

     2: 
     3: # Matches GET "http://host:port/"
     4: get "/" do
     5:   response = "Hello World!"
     6:   debugger
 =>  7:   response
     8: end
     9: 
    10: Kemal.run

pry> response
"Hello World!"
pry> response = "test"
"test"
pry> continue
2022-06-25 06:25:53 UTC 200 GET / 14889.29ms

[asterite]

I think the command expansion should be done somewhere inside Program. It seems the logic is now duplicated. But we can merge this and then unify it.