Module fails to import w/o error, but only when exporting single line function containing $()

[sysread]

The odd circumstances for this to be triggered are:
1. Function is assigned to a variable
2. Function is defined on a single line
3. The function makes use of $(...) to shell out
4. The variable assigned in #1 is returned from the module

This fails without producing any error output:

# scratch.abs
x = f() { $(ls) }
return x

# abs repl
x = require("scratch.abs")
x   # -> null

These do not:

# return one-line, $() function directly
return f() { $(ls) }

# define on multiple lines
x = f() {
    $(ls)
}

return x

# don't use $()
x = f () { return 42 }
return x

[odino]

This is a "known" bug, and the reason we fundamentally deprecated the $() syntax :-S

https://www.abs-lang.org/syntax/system-commands#alternative--syntax

Long story short, the code that parses $() blocks is a bit wonky, and it's just generally easier to parse commands like we parse strings (with a quote charater like ` rather than the weird $() combo). I can probably think of a way of getting around this limitation but I would strongly recommend using backticks for the time being -- they are simpler and require less typing.

In the meantime I'll try giving a crack to fixing parsing $() commands...

[odino]

Also, just to give you an understanding why parsing such commands is a pain, here's an example:

$(echo ")")

Now, the parser would have to know that the ) is in a bash string so it should just ignore it. This comes very easily with:

`echo ")"`

[sysread]

Understood. I honestly preferred the syntax simply because it makes the code much clearer. I didn't realize that it was deprecated from the docs.

[odino]

It's not deprecated as we will keep it supported, at least because embedding commands is a lot easier with this syntax. Though I think it's gonna be bound to have funny cases like this so the recommended way is to use backticks. We don't really have a good way to fix the command parser for good so we might look at it in the future but right now were stuck with these small issue :)