Script arguments can't start with a dash

[DavidPerezIngeniero]

I have a script that has these contents:

#!/usr/bin/env amm

@main
def ini(args: String*) = {
     ...
}

My script can't receive arguments that start with a dash, because they are taken as Ammonite arguments, instead of arguments for my script.

If I try to use e.g.

myScript.sc -?

then this is the ouput:

Error: Unknown option -?
ammonite 0.7.6
Usage: ammonite [options] [<file-args>...] [<args>...]

  -p <value> | --predef <value>
        Any commands you want to execute at the start of the REPL session
  --no-default-predef
        Disable the default predef and run Ammonite with the minimal predef possible
  <file-args>...
        The Ammonite script file you want to execute
  -c <value> | --code <value>
        Pass in code to be run immediately in the REPL
  -x | --execute
        Shim for backwards compatibility - will be removed
  <args>...
        Any arguments you want to pass to the Ammonite script file
  -h <file> | --home <file>
        The home directory of the REPL; where it looks for config and caches
  -f <value> | --predef-file <value>
        Lets you load your predef from a custom location
  -y | --continually
        Lets you run a file over and over, useful for benchmarking purposes
since it lets you hook up a profiler to the long-lived process and
see where all the time is being spent.

  -s | --silent
        Make ivy logs go silent instead of printing though failures will still throw exception
  --repl-api
        Lets you run a script with the `repl` object present; this is
normally not available in scripts and only provided in the
interactive REpl

[lihaoyi]

What if you try myScript.sc -- -?? The -- would tell Ammonite to just forward any subsequent arguments to the script, and not try to parse them itself

In general, I would like a better system to distinguish Ammonite args vs script args, but haven't come up with a good one yet

[DavidPerezIngeniero]

My proposal is simple: arguments before the script file belong to Ammonite.
Arguments that come after the script file, belong to the script.

Example:

amm -s myscript.sc arg1 arg2 --arg3

• -s belongs to amm.
• arg1, arg2, --arg3 belong to myscript.

Do you like the idea?

In this way, there is no need to use --.

[DavidPerezIngeniero]

In addition, my script cannot receive arguments that begin with double slash, even when using --.

Example:

amm myscript.sc -- --mylongoption

[lihaoyi]

Having "pre-file" args be passed to the runtime, and "post-file" args be passed to the script seems like a good compromise to me.

This would require some rewriting of the main method: I don't think the scopts library we're using supports this, and trying to identify the script is probably harder than trying to identify the -- that we're doing now. Overall shouldn't be too much work and if someone wants to implement it (e.g. hint hint @DavidPerezIngeniero) I'll happily merge it

[DavidPerezIngeniero]

OK. I'll try to, when I have time.

[DavidPerezIngeniero]

Any hint please of the related source files to modify?

[DavidPerezIngeniero]

I think I've found it:
https://github.com/lihaoyi/Ammonite/blob/master/amm/src/main/scala/ammonite/Main.scala

[lihaoyi]

yep that's the place

[jatcwang]

Hey @lihaoyi,

I've been trying to write 'standalone' scripts with ammonite, such that I can write an arbitrary program without the user needing to know that it's ammonite running it.

Currently ammonite will always try to parse everything after --, but there are no option to disable that. This means this will blow up with an exception

amm myscript.scala -- --hello

because ammonite's argument parser is expecting another string after --hello (keyword args) . Therefore we should add an option to disable ammonite's command line parsing

What do you think? I've started on this and planning to name the flag -n (--no-arg-parsing)

[hubertp]

@lihaoyi Any chance this PR could be reviewed, or anything along the lines could be implemented? I had a quick look at the the commits that @jtcwang did (https://github.com/hubertp/Ammonite/tree/issue/479) and fixed some simple failing tests. I'm happy to clean it up more if there is a will, because I need that feature.

[lihaoyi]

Fixed in c605d86#diff-d624941e18d4c528c725d4c3c0bd0517R1089

This lets @main methods with varargs properly slurp in everything, allowing you to then use your own custom argument parser. The only caveat is you cannot use -- in your own argument list, since that is reserved to separate Ammonite's arguments from your script's arguments.

Please take a look at the changelog entry which describes this and let me know if this satisfies your requirements

[lihaoyi]

http://www.lihaoyi.com/Ammonite/#0.9.0 is out