repl: support mult-line string-keyed objects

[rubys]

fixes #21657

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[antsmartian]

In version v8.11.3, without this particular check, things works. I'm wondering, now with this code in place, we are sort of re-doing the check (may be?). May be I'm wrong here.

Actually as discussed in the issue, this change broken the partial JSON stuff. The diff is over here:
ebfa8b1#diff-293fefe850253c8c28e2481c0b7f76e2L647

As seen in the comments of PR, looks like partial template literal also broken in latest version. For example:

`io.js ${a
... }`

works in v8/9. But broken in v10x.

[Trott]

@nodejs/repl

[BridgeAR]

@rubys In general, the idea is great. Because this is going in a direction where the code is starting to be properly parsed. I am not sure though if this is the right approach in the current state of the repl. The reason is that the repl itself has so many hacks that it's a nightmare.

It would be really awesome if you would be able to use acorn instead. I am not sure if that would help in this specific moment but I'll have a look into that tomorrow and maybe you could also check that?

[rubys]

@BridegeAR: you are being too kind. It clearly is a hack. Ideally, V8 would be implemented as a streaming parser, but that isn't required for the browser. As Acorn isn't a streaming parser, it isn't likely to be able to help us here.

The root problem is that the JavaScript grammar is ambiguous (at least at the tokenization level), and backtracking is sometimes needed.

Examples of valid JavaScript:

a=1
{a*2}
{a, a}
{a, a*2}
label: {a, a}

Only one of the lines above is an object literal.

[devsnek]

@rubys btw we're working on rewriting the REPL from scratch: https://github.com/nodejs/repl

it might be a good place to experiment with different ways of consuming input, as its still fairly small.

[rubys]

I may have been too quick to discount acorn; it will probably need a patch to be landed to support this use case, but it looks doable. I'm traveling for the next four days, so it may not be until next week that I can take a look at this.

[addaleax]

Can we split this out into a separate file in lib/internal/repl/?

[rubys]

Update: played with acorn on the first flight leg on this trip. Everything needed can be done with a plugin. Will create a separate pull request either later today or this weekend.

[rubys]

See #21805 for an acorn based implementation.