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Mon, 3 Aug 2020 20:48:27 +0000 (UTC) Subject: Re: cleanups with long-term benefits (was Re: [PATCH] schemas: Add vim modeline) To: Nir Soffer References: <20200729185024.121766-1-abologna@redhat.com> <87ime52wxd.fsf@dusky.pond.sub.org> <20200730093732.GB3477223@redhat.com> <87k0ylz0ep.fsf@dusky.pond.sub.org> <20200730132446.GL3477223@redhat.com> <875za33ku1.fsf@dusky.pond.sub.org> <20200731150738.GB3660103@redhat.com> <2cf1a431-9d2c-8ad6-446e-f10b36219764@redhat.com> <87d048i1m2.fsf@dusky.pond.sub.org> <83bbe0b0-c5e0-e3b7-5ba1-5946098370d5@redhat.com> <87ft94klyl.fsf@dusky.pond.sub.org> <490a0786-73f3-411e-4dfe-8c2ae90de251@redhat.com> <17a92222-2627-4961-b57e-1f1f5c86e14a@redhat.com> <6514f2e2-4694-6790-7663-f8a8f6a91e5a@redhat.com> From: John Snow Message-ID: Date: Mon, 3 Aug 2020 16:48:26 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=jsnow@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/03 02:37:52 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Eduardo Habkost , qemu-block , "Michael S. Tsirkin" , Jason Wang , Juan Quintela , Yuval Shaia , Markus Armbruster , QEMU Developers , Gerd Hoffmann , Andrea Bolognani , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , Paolo Bonzini , Michael Roth , "Dr. David Alan Gilbert" , Stefan Berger Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/3/20 3:54 PM, Nir Soffer wrote: > On Mon, Aug 3, 2020 at 9:19 PM John Snow wrote: >> >> On 8/3/20 2:16 PM, Paolo Bonzini wrote: >>> On 03/08/20 20:10, John Snow wrote: >>>> Heresy: >>>> >>>> Docstrings could become part of the data format so they can be parsed, >>>> analyzed and validated. Parsers largely treat comments like non-semantic >>>> information and discard it. Round-trip parsers that preserve comments in >>>> any language are extremely rare. >>>> >>>> If the docstrings are relevant to the generator and aren't discardable, >>>> they should be fully-fledged data members. >>>> >>>> In a prototype I had for a YAML format, I just promoted docstrings >>>> directly to fields, so I could allow clients to query help text for >>>> individual commands. >>> >>> This would be actually a good idea, but somebody has to write the code. >>> Each field's docstring should be attached to the field, however---no >>> parsing needed only looking at the tree. Take a look at what Nir posted: >>> >>>> Here is the patch adding schema convertor from qemu "json" format to >>>> standard yaml: >>>> https://github.com/oVirt/vdsm/commit/e57b69e72987c0929b20306c454835b52b5eb7ee >>>> >>>> The current version of the new yaml based schema: >>>> https://github.com/oVirt/vdsm/blob/master/lib/vdsm/api/vdsm-api.yml >>> >>> >>> VmDiskDevice: &VmDiskDevice >>> added: '3.1' >>> description: Properties of a VM disk device. >>> name: VmDiskDevice >>> properties: >>> - description: Indicates if writes are prohibited for the >>> device >>> name: readonly >>> type: boolean >>> >>> - description: The size of the disk (in bytes) >>> name: apparentsize >>> type: uint >>> >>> etc. >>> >>> Paolo >>> >> >> I was working on a small prototype that used something that looked like >> this; the "*opt" format was traded for "?opt", but otherwise: >> >> >> struct: >> name: AudiodevPerDirectionOptions >> doc: > >> General audio backend options that are used for both >> playback and recording. >> since: '4.0' >> members: >> >> ?mixing-engine: > > This optimizes for writing instead of reading. > Following a "path of least resistance" from the existing QAPI language, clearly carrying over the '*optional' syntax. > optional: true > > Would be nicer to read, but more important is all the tools parsing > this schema in multiple languages that will have code like: > > def is_optional(node): > return node.name.startswith("?") > > Instead of : > > if node.optional: > ... > > Or maybe better: > > if node.required: > > Because it seems that more nodes are optional, so focusing on the required > items will make the schema shorter and more clear. > >> type: bool >> default: 'true' >> since: '4.2' >> doc: | >> Use QEMU's mixing engine to mix all streams inside QEMU and >> convert audio formats when not supported by the backend. > > Using | is nicer than >-. Not sure what is the difference. In vdsm we don't use > anything and I think it causes trouble when indenting text. > I believe when I wrote this example I was trying to highlight the different space consumption styles for the purposes of demonstrating what it would do to Sphinx document generation support. ultimately, there's not really a way to enforce one or the other style post-parse. >> When set to off, fixed-settings must be also off. >> >> ?fixed-settings: >> type: bool >> default: 'true' > > Why is the default a string and not the actual type? > I'm going to be honest: I forget. I was playing around with the idea of documenting defaults for the purposes of documentation, but not necessarily for performing the actual code generation of those defaults. I believe I specified this field as a string in my grammar and `5` would get promoted to "5", but `true` caused a type error. Doing something in a type-safe way seemed ... harder. So I didn't. >> doc: >- >> Use fixed settings for host input/output. >> When off, frequency, channels and format must not be specified. >> >> ?frequency: >> type: bool >> default: '44100' >> doc: >- >> frequency to use when using fixed settings. >> >> ?channels: >> type: 'uint32' >> default: 2 > > Here you use the real type, and this is nicer. > >> doc: >- >> Number of channels when using fixed settings. >> >> ?voices: >> type: 'uint32' >> default: 1 >> doc: "Number of voices to use." >> >> ?format: >> type: 'AudioFormat' >> default: 's16' >> doc: "Sample format to use when using fixed settings." >> >> ?buffer-length: >> type: 'uint32' >> doc: 'The buffer length, in microseconds.' >> >> features: >> my-cool-feature: >> since: '6.0' >> doc: 'This is, no doubt, an extremely cool feature.' >> >> my-bad-feature: >> doc: 'This is a very bad feature. I am sorry for making it.' >> since: '1.0' >> deprecated: '5.9' > > Good example :-) > >> >> >