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Lunev" , Cleber Rosa , Stefan Hajnoczi , qemu-devel , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , Paolo Bonzini , Dominik Csapak , Eduardo Habkost Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/24/19 8:41 AM, Daniel P. Berrang=C3=A9 wrote: >> * scripts/qmp/qmp-shell >> >> Half-hearted attempt at a human-friendly wrapper around the JSON >> syntax. I have no use for this myself. > I use this fairly often as its a useful debugging / experimentation > / trouble shooting tool. There's similar ish functionality in > virsh qemu-monitor-command. I think there's scope of a supported > tool here that can talk to libvirt or a UNIX socket for doing > QMP commands, with a friendlier syntax & pretty printing.=20 >=20 qmp-shell is one of my go-to tools for working through bitmap workflows where we don't have convenience commands yet, as some of the setups required for fleecing et al involve quite a number of steps. I can copy-paste raw JSON into a socket, but personally I like seeing my commands neatly organized in a format where I can visually reduce them to their components at a glance. (What I mean is: It's hard to remember which QMP commands you've barfed into a terminal because JSON is hard to read and looks very visually repetitive.) I tried to rewrite qmp-shell late last year, actually. I wanted to write a new REPL that was json-aware in some manner such that you could write multi-line commands like this: > example-command arg=3D{ "hello": "world" } This requires, sadly, a streamable JSON parser. Most JSON parsers built into Python as-is simply take a file pointer and consume the entirety of the rest of the stream -- they don't play very nice with incomplete input or input that may have trailing data, e.g.: > example-command arg=3D{ "hello": "world" } arg2=3D{ "oops!": "more json!" } Also, due to the nature of JSON as being a single discrete object and never a stream of objects, no existing JSON parser really supports the idea of ever seeing more than one object per buffer. ...So I investigated writing a proper grammar for qmp-shell. Unfortunately, this basically means including the JSON grammar as a subset of the shell grammar and writing your own parser for it entirely. I looked into using Python's own lexer; but it's designed to lex *python*, not *json*. I got a prototype lexer working for this purpose under a grammar that I think reflects JSON, but I got that sinking feeling that it was all more trouble than it was worth, and scrapped working on it any further. I did not find any other flex/yacc-like tools that seemed properly idiomatic or otherwise heavily specialized. I gave up on the idea of writing a new parser. I'd love to offer a nice robust QMP shell that is available for use by end users, but the syntax of the shell will need some major considerations. (Coffee break) The other thing I wanted to do was offer a TUI-esque backlog of commands; something reminiscent of mutt or TUI mail clients. Arrow keys could be used to browse the list of previous TX/RX objects, spacebar/enter to view them in detail; '?' to pull up the relevant QAPI documentation in a side-pane. That sort of thing. I thought it would be nice to offer an "IRC-esque" view of the QMP protocol where new events stream in from the bottom, and new commands can be typed into the buffer bar. (I found no convincing way to combine e.g. readline with a TUI interface. It seemed like you get one or the other.) Allowing qmp-shell to show events received asynchronously would also be a big leap up from the current shell. It's a lot of fantasy stuff I wasn't *quite* able to tie together. --js