Make `list` display the next set of lines when the empty command is sent

[dmlary]

Note: This is a feature request.

Please answer the following before submitting your issue:

Note: Please include any substantial examples (debug session output, stacktraces, etc) as linked gists.

1. What version of Delve are you using (dlv version)?

Delve Debugger
Version: 1.4.0
Build: $Id: 67422e6f7148fa1efa0eac1423ab5594b223d93b $

2. What version of Go are you using? (go version)? go version go1.14.2 linux/amd64

3. What operating system and processor architecture are you using? x86_64 GNU/Linux

4. What did you do?

• list <func> # output 10 lines of code
• <pressed enter> # output same 10 lines of code

5. What did you expect to see?

Next 10 lines of code, similar to gdb & lldb. Makes displaying source while debugging more convenient.

6. What did you see instead?

The same 10 lines of code

Example:

(dlv) list snode.attr
Showing /go/pkg/mod/bazil.org/[email protected]/fs/serve.go:492 (PC: 0x56d9d3)
 487:		//     - hold Server.meta while calling wg.Add, then unlock
 488:		//     - do NOT try to reacquire Server.meta
 489:		wg sync.WaitGroup
 490:	}
 491:
 492:	func (sn *serveNode) attr(ctx context.Context, attr *fuse.Attr) error {
 493:		err := nodeAttr(ctx, sn.node, attr)
 494:		if attr.Inode == 0 {
 495:			attr.Inode = sn.inode
 496:		}
 497:		return err
(dlv)
Showing /go/pkg/mod/bazil.org/[email protected]/fs/serve.go:492 (PC: 0x56d9d3)
 487:		//     - hold Server.meta while calling wg.Add, then unlock
 488:		//     - do NOT try to reacquire Server.meta
 489:		wg sync.WaitGroup
 490:	}
 491:
 492:	func (sn *serveNode) attr(ctx context.Context, attr *fuse.Attr) error {
 493:		err := nodeAttr(ctx, sn.node, attr)
 494:		if attr.Inode == 0 {
 495:			attr.Inode = sn.inode
 496:		}
 497:		return err

[aarzilli]

There's an edit command that can open the source code at the current line. You can even set it up to open the source in a different window easily. I've always thought the behavior of list in gdb was archaic, designed for physical teletypes from the '70s.

[dmlary]

It is archaic, but occasionally you're working in an environment like that. For example, writing a user-space filesystem with bazil.org/fuse on a mac, which doesn't support mac, I'm forced to run all tests & debugging within a docker image.

[jginsburgn]

+1 Also, there should be a way to see the previous lines and to set the number of lines printed when issuing list.

[jcass8695]

Not to derail OP's original issue, but I would like to add my +1 to @jginsburgn's suggestion:

set the number of lines printed when issuing list.

It would be useful to be able to print more than the 5 lines either side of the current line, similar to grep's A, B and C flags.

[aarzilli]

That can already be done:

(dlv) config source-list-line-count 10

[jcass8695]

I think it might be more intuitive and user-friendly to have something like list -A 15 -B 12 or list -C 17. If you know roughly where in the codebase I could get started, I might have time over the next few weekends to take a look.

[aarzilli]

List takes a location expression as an argument, which can be anything. It's difficult to change it to also take other arguments in an unambiguous way. Also I still think there's little need for this when there's edit.

[jcass8695]

Fair enough 👍🏻