John Snow <js...@redhat.com> writes: > On 1/27/20 9:35 AM, Kevin Wolf wrote: >> Am 24.01.2020 um 10:50 hat Daniel P. Berrangé geschrieben: >>> On Thu, Jan 23, 2020 at 04:07:09PM -0500, John Snow wrote: >>>> Well, sure. The context of this email was qmp-shell though, which is >>>> meant to help facilitate the entry of JSON commands so that you *can* >>>> indeed just forego the CLI/HMP entirely. >>>> >>>> If you are of the opinion that every user of QEMU should be copy/pasting >>>> JSON straight into a socket and we should delete qmp-shell, that's >>>> certainly a fine opinion. >>> >>> I think part of the pain of qmp-shell comes from the very fact that >>> it is trying to be an interactive shell. This points people towards >>> interactively typing in the commands, which is horrific when you get >>> anywhere near the JSON, or even dot-notation traditional commands. >>> >>> If it was just a qmp-client that was single shot, we'd encourage >>> people to create the JSON in a sensible way - vim/emacs/whatever. >> >> I don't see how this is sensible. QMP commands are something that I >> reuse even less than VM configurations, so creating a one-off file for >> each would take me a lot more time and I would still have to type the >> same JSON code that I have to type with -qmp stdio. >> >> The reason it is and should be an interactive shell is that I'm >> interacting with it. Switching back and forth between a text editor and >> a shell to actually send the command to QEMU would make things only even >> more cumbersome than they already are. >> >>> Bash/dash/zsh/$whatever is their interactive shell, with massively >>> more features than qmp-shell. You have command history, autocomplete, >>> conditional and looping constructs, and everything a normal shell >>> offers. >> >> If I wanted to program a QMP client, I would use Python. For me, >> conditionals and loops are completely out of scope for a QMP shell. I >> just want an easy way to tell QEMU to do something specific. >> >> A command history already exists for qmp-shell. It's better than bash >> because it doesn't mix QMP history with whatever else I do on my >> computer. >> >> Autocomplete in qmp-shell doesn't exist, as far as I know, but if >> implemented, it could be a lot more useful than bash completion because >> it could offer key completion based on the QMP schema. >> > > It does have tab completion for command names, but it does not know > about or remember argument fields. It does not have autocomplete or > typing hints like FiSH or bash ^r. > > I would like to change this, actually, by making the docstrings in QAPI > schema a first class citizen of the spec and allowing them to be > introspectable via the socket directly. > > (I.e., you can get the list of arguments and the docstrings that > accompany them over the wire so you can display it in the client.)
You need doc strings for help, but not for completion. query-qmp-schema's reply is already rather big: 130KiB. The size of docs in an JSON encoding useful to qmp-shell we can only estimate. Plain text docs/interop/qemu-qmp-ref.txt is 505KiB. I guess we'd make the doc strings optional. > Problem I'm having with qmp-shell is, like Kevin says below ... > >> This is in fact a big part of the problem that qmp-shell really needs to >> solve before it can replace HMP: How to make writing commands at least >> almost as simple as with HMP. If I can just press tab a few times to >> cycle through the available options for the command, that would already >> be a massive improvement over writing JSON manually (which you would >> still have to do with your text-file based approach, without any >> QMP-specific support). >> > > ... I can't figure out how to make writing commands simple. > > When you have a "simple" command, the abstraction works OK; you can type > key=val pairs and go about your way. qmp-shell tries to improve on the JSON syntax by inventing its own, but... > As soon as you have anything nested, the gossamer-thin illusion is > destroyed. ... it does a halfhearted job. I'm deeply skeptical of any solution that starts with inventing a new language. Start with examining existing ones instead. > I investigated making this a little easier by adding a parser > that could read directly from stdin and would allow multi-line JSON > inputs as arguments. > > (Like the python shell does it, for example: When you have a dictionary > opening brace, it lets you continue to the next line.) > > I was a little disheartened that most JSON parsers in python expect to > consume buffered objects and generally consume the entire buffer -- it > didn't seem to play nice with the idea of wanting to parse from STDIN > directly. > > > So: > > - I think qmp-shell is worth having, especially if polished > (autocomplete, docstrings, argument hints, etc). > > - Kevin mentioned getting this into the GTK shell. I think that would be > great, as a step to help phase out HMP. > > - I think getting rid of HMP is good because I don't care for the idea > of supporting two monitor protocols. One schema, one parser, one truth. > > - I do, however, like the idea of having a non-rigorous monitor that > lets us get away with murder when we need to. HMP is useful for > debugging, prototypes and other things where the rigor and permanence of > a QAPI schema feels too burdensome. We discussed relaxing the rules for such QMP commands. In particular, they could return just a string. Fine with me as long as we make perfectly clear these commands are not stable interfaces. > - So: maybe a turbocharged qmp-shell can offer some similar kinds of > convenience commands that are build on top of real QMP. Sugar logic and > other fanciful things could be implemented there in qmp-shell as > extensions. You'd get a stock pile of them with your QEMU install that > help you do certain tasks quickly and trivially. > > - Given all the above, I am willing to try to save, polish, or re-design > qmp-shell; but am a bit starved for ideas on the syntax... This is why I > was spending a bit of time talking about our flattening to dot syntax, > and other projects related to representing hierarchical data. > > Would really love to hear ideas on what a good interactive shell syntax > for a JSON-fueled schema would look like. We can't possibly be the first ones asking this question. > Any prior art, other projects, and reading anyone can recommend would be > nice. [...]
