Add REPL

[kyranet]

It would be very nice to have a REPL in deno, which would help us to test code quickly. Currently, it exits the process with error code 1 and the message "No input script specified.".

[ry]

Yes definitely. I’d like to wait until a couple of important refactors are landed before trying to do the REPL: #733 and #721

There’s some debate as to whether we should use a readline/repl library from rust or develop our own in JS (as we did in node). I am leaning towards using a rust lib...

(I also would like to have a command line debugger like node debug. It’s one of my major regrets that the CLI debugger in Node had very little improvements after I made it. It is still buggy and barely usable. We can fix that here.)

[ry]

Both of the above mentioned issues are now solved. I'm open to patches for REPL now.

Thoughts:

• I think this should be done using a Rust readline crate (e.g. https://github.com/kkawakam/rustyline). Discuss in this issue first which crate you would use.
• I am open to a pure JS implementation, but skeptical that this can be done more easily than with a rust lib.
• Windows must be supported.
• Each eval could be done using Isolate::execute()
• We don't need to support TS for the first version.

[cedric05]

will try to implement. i'm new to this, don't stop because of me

[cedric05]

couldn't add rustyline to third_party, is there an easy way to add new packages to existing deno project. generating rlib is one heck of thing, couldn't figure out with present build.gn files

[cedric05]

came across https://github.com/sfackler/cargo-tree, which will print dependencies in tree, will try to change build files.

[cedric05]

using rustyline i created a repl loop, but i'm not able to import any deno modules/functions defined in deno.ts . how can we import them from pure js runtime ?

for reference branch: https://github.com/denoland/deno/compare/master...cedric05:repl?expand=1
deno_third_party: https://github.com/denoland/deno_third_party/compare/master...cedric05:master?expand=1
changes
@ry

[ry]

@cedric05 cool! we will have to hook into the ES module import hooks in V8 or pass the input thru TS... if you upload your patch as a PR, I’ll take a look and provide some more concrete guidance

[cedric05]

i can raise pr, but this is half baked

[ry]

@cedric05 that’s fine - just add WIP to the title

[cedric05]

raised #947.

[kitsonk]

This can be closed. We should handle any enhancements to the REPL under different issues.