cli options to torchbear apps

[naturallymitchell]

gut showed, then mp followed in using bash scripts, which as Sharaf puts it is EVIL I agree we need something robust I personally like config files but we're gonna put these apps system-wide, starting with mp so are they goin in with bash?

[sineemore]

from discussion on Discord

torchbear can be a decent Lua interpreter.

Linux has a cool feature named shebang: https://en.wikipedia.org/wiki/Shebang_(Unix)

#!/bin/sh
printf 'Hello, %s!\n' 'Found Patterns Studio'

Shebang line can contain any program:

#!/bin/echo

If we save this file in /usr/bin/myapp and run it, it will output:

$ myapp
/usr/bin/myapp
$
$ myapp 123
/usr/bin/myapp 123

So, what happens under the hood:

/usr/bin/echo /usr/bin/myapp 123
      ^             ^         ^
      |             |         |
      |             |        arguments from command line
      |            full path to `myapp`
     shebang line

The torchbear shebang may look like this:

#!/usr/bin/torchbear --run

--[[
    Here follows Lua code
--]]

And the actual call will be:

$ /usr/bin/torchbear --run filename [argument...]

[sineemore]

So the actual implementation will require a new command line flag (like --run), that will specify location of Lua file to run. When the flag is provided torchbear should use all non-option arguments to create a Lua global array arg similar to standard Lua interpreter.

Also torchbear should set Lua include path to dirname of the command passed in --run flag. One caveat here is that the provided command may be a link (very common to place links into PATH directories). Then torchbear should dereference it before setting the include path.

[naturallymitchell]

Torchbear installs to different paths depending on the platform, so I believe this will help: Shell script shebang for unknown path

[sineemore]

Yeap, sure. The env trick will work as well.

[sineemore]

After some research turns out we can't use the --run option:

When setting shebang line to #!/usr/bin/env torchbear --run and running it, the output is:

$ LANG= sample-torch
/usr/bin/env: 'torchbear --run': No such file or directory
/usr/bin/env: use -[v]S to pass options in shebang lines
$

env receives torchbear --run as a single argument. The proposed -S option is not standard and won't work on non GNU env implementation.

---

We can drop the --run flag and start torchbear in CLI mode, when there is at least one non-option value in the arguments:

torchbear -a 1 -b 2 /file/to/run

Here /file/to/run is first non option argument. All arguments that follow it (including itself) must be passed to Lua via arg global. The Lua package.path must be set as well.

This way the final shebang line will be:

#!/usr/bin/env torchbear

[naturallymitchell]

Sounds good

[sineemore]

Oh, and we should not forget about -- thing.

[naturallymitchell]

Huh

[sineemore]

Quote from POSIX Utility Conventions:

Guideline 10: The first -- argument that is not an option-argument should be accepted as a delimiter indicating the end of options. Any following arguments should be treated as operands, even if they begin with the '-' character.

http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap12.html

[naturallymitchell]

it seems like we should completely switch to #!/usr/bin/env torchbear, where possible, instead of expecting to call torchbear directly on an app. this is just like using python and lua, ie any scripting language.

so we just need https://github.com/foundpatterns/torchbear/issues/19, which seems pretty doable, to make torchbear really light up

@sineemore how hard do you think this issue will be?

[sineemore]

Depends on the argument parsing. I don't know much about clap, maybe @dariusc93 can suggest a thing. Most part of required code was written in pull request I've closed recently. I guess it only lacks the proper argument parsing and setting command arguments in Lua arg global table. Doable things.

And REPL is completely another kind of beast. But yet again, since there is a pure Lua implementation I don't think it's a hard thing.

[naturallymitchell]

can way-cooler's clap ArgMatches help us?

and way-cooler's main.rs

[naturallymitchell]

torchbear can be a decent Lua interpreter.

I took this for granted. this is its first first killer app

[sineemore]

Relevant pull request: https://github.com/foundpatterns/torchbear/pull/158

[dariusc93]

Implemented in https://github.com/foundpatterns/torchbear/pull/158