debugger: introduce exec method for debugger

[JacksonTian]

In debugger, the usage of repl very ugly. I'd like there is a p
like gdb. So the exec is coming.

Usage:

$ ./iojs debug ~/git/node_research/server.js
< Debugger listening on port 5858
connecting to 127.0.0.1:5858 ... ok
break in /Users/jacksontian/git/node_research/server.js:1
> 1 var http = require('http');
2
3 http.createServer(function (req, res) {
debug> exec('process.title')
/Users/jacksontian/git/io.js/out/Release/iojs
debug>

And the repl:

debug> repl
Press Ctrl + C to leave debug repl
> process.title
'/Users/jacksontian/git/io.js/out/Release/iojs'
debug>
(^C again to quit)

The enter and leave debug repl is superfluous.

[bnoordhuis]

Minor style issue: no space after function keyword.

[bnoordhuis]

LGTM sans style nit.

[JacksonTian]

thanks @bnoordhuis

[chrisdickinson]

Curious: down the line is there interest in moving to a more python pdb-style debugger, where the interface is a REPL by default and will evaluate any expression inline, but still respond to debugging commands?

[monsanto]

@chrisdickinson +1 this tripped me up when I first started playing with Node

[JacksonTian]

@chrisdickinson hope there is an idb or ndb command.

[JacksonTian]

ping anyone?

[silverwind]

Not sure this is the best approach. exec('') seems a bit too verbose.

I've recently experimented with the debugger for the first time, and was a bit surprised it wasn't a real repl. How about actually making it a repl and adding all debug related commands to the existing list of commands shown in the repl with .help?

This would of course be an incompatible change, but having all commands prefixed with a dot would be my preferred method. Maybe add a short print to refer to .help on debug start.

[rlidwka]

This would of course be an incompatible change, but having all commands prefixed with a dot would be my preferred method.

I use debugger heavily, and most commands I use are n, s and c. So I don't really like the idea to prefix them with dots: that's twice the amount of characters to type.

[JacksonTian]

@silverwind the exec(exp) is a shorthand of repl + exp + control/c, and not an incompatible change.

[chrisdickinson]

I think we should take a page from python's book and allow those commands unprefixed, but if the line isn't a known command treat it as a repl utterance.

On May 10, 2015, at 6:01 AM, Alex Kocharin notifications@github.com wrote:

This would of course be an incompatible change, but having all commands prefixed with a dot would be my preferred method.

I use debugger heavily, and most commands I use are n, s and c. So I don't really like the idea to prefix them with dots: that's twice the amount of characters to type.

—
Reply to this email directly or view it on GitHub.

[rlidwka]

I think we should take a page from python's book

That one where n+1 means next, but 1+n means local variable access?

>>> import pdb
>>> pdb.run('for n in range(1, 100):\n n')
> <string>(1)<module>()
(Pdb) n
> <string>(2)<module>()
(Pdb) print n
1
(Pdb) n+1
> <string>(1)<module>()
(Pdb) 1+n
2

[silverwind]

One way around this variable name problem could be to require a semicolon to access local variables, so n; would get you the variable, n would execute next.

[jasnell]

@nodejs/collaborators ... anyone have any idea on the status of this? Is it still something that's wanted? /cc @JacksonTian

[JacksonTian]

yes, repl is ugly.

[silverwind]

@JacksonTian can you at least make it exec process.title or short e process.title?

[JacksonTian]

ok.

[JacksonTian]

@silverwind Implement exec process.title is ok. I'd like to know whether the command expr style fit the API style, the other command meet command() function call style.

[silverwind]

needs to be node now ;)

[bnoordhuis]

This should probably use an anchoring match (i.e. /^\s*exec) so it won't get confused by e.g. "exec exec exec" as the input.

EDIT: Can you add a regression test for that while you're at it? Thanks.

[JacksonTian]

Thanks @bnoordhuis , I updated the commit.

[cjihrig]

Could you use an arrow function callback and get rid of self.

[JacksonTian]

The PR was submitted long time ago : ). updated.

[cjihrig]

Thanks, LGTM.

[bnoordhuis]

LGTM2. I can't start the CI though, seems to be down at the moment.

[bnoordhuis]

And it's up again: https://ci.nodejs.org/job/node-test-pull-request/767/

[jasnell]

Failures in CI look unrelated. Will get this landed.

[jasnell]

Landed in b33e9da

[MylesBorins]

Is this something we would want in LTS? /cc @nodejs/lts

[jasnell]

hmmm... good question. lts-agenda label applied.

[MylesBorins]

lts wg has agreed this poses little risk. Added lts-watch label and we can add this to the next LTS semver minor bump