Re: [PATCH 1/9] qapi: New special feature flag "unstable"

Kashyap Chamarthy <kchamart(a)redhat.com&gt; writes: > On Mon, Oct 25, 2021 at 07:25:24AM +0200, Markus Armbruster wrote:

> Looks like there's another stable property with an "x-" prefix: > "x-remote-object", part of QOM type @RemoteObjectProperties. The union branch 'x-remote-object' isn't flagged 'unstable' (because union branches can't have feature flags), but the enumeration value 'x-remote-object' is. Sufficient, because you can't use the branch without using the enumeration value. Admittedly subtle.

I wrote a bit of code (appended) to make sure I don't miss names.

> Given the above "x-" properties are now stable, I take it that they > cannot be renamed now, as they might break any tools using them? My > guess is the tedious way is not worth it: deprecate them, and add the > non-x variants as "synonyms". "x-use-canonical-path-for-ramblock-id" goes back to commit fa0cb34d22 "hostmem: use object id for memory region name with >= 4.0" (v4.0). It may have been intended to be internal back then. It wasn't anymore when commit 8db0b20415 "machine: add missing doc for memory-backend option" (v6.0) documented it: And document that x-use-canonical-path-for-ramblock-id, is considered to be stable to make sure it won't go away by accident. x- was intended for unstable/iternal properties, and not supposed to be stable option. However it's too late to rename (drop x-) it as it would mean that users will have to mantain both x-use-canonical-path-for-ramblock-id (for QEMU 5.0-5.2) versions and prefix-less for later versions. Igor's reasoning still applies. "x-origin" has always been stable. Same argument.

commit 415b71a9f6e5bc37e84895d2e767cf4cfacd279b (HEAD) Author: Markus Armbruster <armbru(a)redhat.com&gt; Date: Sat Oct 9 09:01:21 2021 +0200 qapi: Find x- without feature unstable DBG diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py index b7b3fc0ce4..f2af1d7eea 100644 --- a/scripts/qapi/schema.py +++ b/scripts/qapi/schema.py @@ -14,6 +14,8 @@ # TODO catching name collisions in generated code would be nice +import sys + from collections import OrderedDict import os import re @@ -118,6 +120,11 @@ def describe(self): return "%s '%s'" % (self.meta, self.name) +def check_have_feature_unstable(name, info, features): + if name.startswith('x-') and 'unstable' not in (f.name for f in features): + print(QAPISemError(info, f"XXX %{name} %{features}"), file=sys.stderr) + + class QAPISchemaVisitor: def visit_begin(self, schema): pass @@ -718,6 +725,7 @@ def __init__(self, name, info, ifcond=None, features=None): self.features = features or [] def connect_doc(self, doc): + check_have_feature_unstable(self.name, self.info, self.features) super().connect_doc(doc) if doc: for f in self.features: @@ -745,6 +753,7 @@ def __init__(self, name, info, typ, optional, ifcond=None, features=None): self.features = features or [] def check(self, schema): + check_have_feature_unstable(self.name, self.info, self.features) assert self.defined_in self.type = schema.resolve_type(self._type_name, self.info, self.describe) @@ -789,6 +798,7 @@ def __init__(self, name, info, doc, ifcond, features, def check(self, schema): super().check(schema) + check_have_feature_unstable(self.name, self.info, self.features) if self._arg_type_name: self.arg_type = schema.resolve_type( self._arg_type_name, self.info, "command's 'data'") @@ -844,6 +854,7 @@ def __init__(self, name, info, doc, ifcond, features, arg_type, boxed): def check(self, schema): super().check(schema) + check_have_feature_unstable(self.name, self.info, self.features) if self._arg_type_name: self.arg_type = schema.resolve_type( self._arg_type_name, self.info, "event's 'data'")