On Mon, Oct 25, 2021 at 1:26 AM Markus Armbruster <arm...@redhat.com> wrote:
> By convention, names starting with "x-" are experimental. The parts
> of external interfaces so named may be withdrawn or changed
> incompatibly in future releases.
>
> Drawback: promoting something from experimental to stable involves a
> name change. Client code needs to be updated.
>
> Moreover, the convention is not universally observed:
>
> * QOM type "input-barrier" has properties "x-origin", "y-origin".
> Looks accidental, but it's ABI since 4.2.
>
> * QOM types "memory-backend-file", "memory-backend-memfd",
> "memory-backend-ram", and "memory-backend-epc" have a property
> "x-use-canonical-path-for-ramblock-id" that is documented to be
> stable despite its name.
>
> We could document these exceptions, but documentation helps only
> humans. We want to recognize "unstable" in code, like "deprecated".
>
> Replace the convention by a new special feature flag "unstable". It
> will be recognized by the QAPI generator, like the existing feature
> flag "deprecated", and unlike regular feature flags.
>
> This commit updates documentation and prepares tests. The next commit
> updates the QAPI schema. The remaining patches update the QAPI
> generator and wire up -compat policy checking.
>
> Signed-off-by: Markus Armbruster <arm...@redhat.com>
> ---
> docs/devel/qapi-code-gen.rst | 9 ++++++---
> tests/qapi-schema/qapi-schema-test.json | 7 +++++--
> tests/qapi-schema/qapi-schema-test.out | 5 +++++
> 3 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/docs/devel/qapi-code-gen.rst b/docs/devel/qapi-code-gen.rst
> index 4071c9074a..38f2d7aad3 100644
> --- a/docs/devel/qapi-code-gen.rst
> +++ b/docs/devel/qapi-code-gen.rst
> @@ -713,6 +713,10 @@ member as deprecated. It is not supported elsewhere
> so far.
> Interfaces so marked may be withdrawn in future releases in accordance
> with QEMU's deprecation policy.
>
> +Feature "unstable" marks a command, event, enum value, or struct
> +member as unstable. It is not supported elsewhere so far. Interfaces
> +so marked may be withdrawn or changed incompatibly in future releases.
> +
>
> Naming rules and reserved names
> -------------------------------
> @@ -746,9 +750,8 @@ Member name ``u`` and names starting with ``has-`` or
> ``has_`` are reserved
> for the generator, which uses them for unions and for tracking
> optional members.
>
> -Any name (command, event, type, member, or enum value) beginning with
> -``x-`` is marked experimental, and may be withdrawn or changed
> -incompatibly in a future release.
> +Names beginning with ``x-`` used to signify "experimental". This
> +convention has been replaced by special feature "unstable".
>
> Pragmas ``command-name-exceptions`` and ``member-name-exceptions`` let
> you violate naming rules. Use for new code is strongly discouraged. See
> diff --git a/tests/qapi-schema/qapi-schema-test.json
> b/tests/qapi-schema/qapi-schema-test.json
> index b677ab861d..43b8697002 100644
> --- a/tests/qapi-schema/qapi-schema-test.json
> +++ b/tests/qapi-schema/qapi-schema-test.json
> @@ -273,7 +273,7 @@
> 'data': { 'foo': { 'type': 'int', 'features': [ 'deprecated' ] } },
> 'features': [ 'feature1' ] }
> { 'struct': 'FeatureStruct2',
> - 'data': { 'foo': 'int' },
> + 'data': { 'foo': { 'type': 'int', 'features': [ 'unstable' ] } },
> 'features': [ { 'name': 'feature1' } ] }
> { 'struct': 'FeatureStruct3',
> 'data': { 'foo': 'int' },
> @@ -331,7 +331,7 @@
> { 'command': 'test-command-features1',
> 'features': [ 'deprecated' ] }
> { 'command': 'test-command-features3',
> - 'features': [ 'feature1', 'feature2' ] }
> + 'features': [ 'unstable', 'feature1', 'feature2' ] }
>
> { 'command': 'test-command-cond-features1',
> 'features': [ { 'name': 'feature1', 'if': 'TEST_IF_FEATURE_1'} ] }
> @@ -348,3 +348,6 @@
>
> { 'event': 'TEST_EVENT_FEATURES1',
> 'features': [ 'deprecated' ] }
> +
> +{ 'event': 'TEST_EVENT_FEATURES2',
> + 'features': [ 'unstable' ] }
> diff --git a/tests/qapi-schema/qapi-schema-test.out
> b/tests/qapi-schema/qapi-schema-test.out
> index 16846dbeb8..1f9585fa9b 100644
> --- a/tests/qapi-schema/qapi-schema-test.out
> +++ b/tests/qapi-schema/qapi-schema-test.out
> @@ -308,6 +308,7 @@ object FeatureStruct1
> feature feature1
> object FeatureStruct2
> member foo: int optional=False
> + feature unstable
> feature feature1
> object FeatureStruct3
> member foo: int optional=False
> @@ -373,6 +374,7 @@ command test-command-features1 None -> None
> feature deprecated
> command test-command-features3 None -> None
> gen=True success_response=True boxed=False oob=False preconfig=False
> + feature unstable
> feature feature1
> feature feature2
> command test-command-cond-features1 None -> None
> @@ -394,6 +396,9 @@ event TEST_EVENT_FEATURES0 FeatureStruct1
> event TEST_EVENT_FEATURES1 None
> boxed=False
> feature deprecated
> +event TEST_EVENT_FEATURES2 None
> + boxed=False
> + feature unstable
> module include/sub-module.json
> include sub-sub-module.json
> object SecondArrayRef
> --
> 2.31.1
>
>
Feels odd to combine the doc update *and* test prep, but eh, whatever.
Reviewed-by: John Snow <js...@redhat.com>
