[RFC PATCH 13/19] qapi: New special feature flag "deprecated"

[Markus Armbruster <armbru@redhat.com>]

Unlike regular feature flags, the new special feature flag
"deprecated" is recognized by the QAPI generator.  For now, it's only
permitted with commands and events.  It will be put to use shortly.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 docs/devel/qapi-code-gen.txt                    | 6 ++++++
 scripts/qapi/schema.py                          | 6 ++++++
 tests/Makefile.include                          | 1 +
 tests/qapi-schema/features-deprecated-type.err  | 2 ++
 tests/qapi-schema/features-deprecated-type.json | 3 +++
 tests/qapi-schema/features-deprecated-type.out  | 0
 tests/qapi-schema/qapi-schema-test.json         | 4 ++--
 tests/qapi-schema/qapi-schema-test.out          | 4 ++--
 8 files changed, 22 insertions(+), 4 deletions(-)
 create mode 100644 tests/qapi-schema/features-deprecated-type.err
 create mode 100644 tests/qapi-schema/features-deprecated-type.json
 create mode 100644 tests/qapi-schema/features-deprecated-type.out

diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index eaeedc7bd3..e6ef93544e 100644
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -665,6 +665,12 @@ Example:
   'features': [ 'allow-negative-numbers' ] }
 
 
+==== Special features ====
+
+Feature "deprecated" makes a command or event as deprecated.  It is
+not supported elsewhere so far.
+
+
 === Naming rules and reserved names ===
 
 All names must begin with a letter, and contain only ASCII letters,
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 639140fceb..840d119c6d 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -179,6 +179,12 @@ class QAPISchemaType(QAPISchemaEntity):
             return None
         return self.name
 
+    def check(self, schema):
+        QAPISchemaEntity.check(self, schema)
+        if 'deprecated' in [f.name for f in self.features]:
+            raise QAPISemError(
+                self.info, "feature 'deprecated' is not supported for types")
+
     def describe(self):
         assert self.meta
         return "%s type '%s'" % (self.meta, self.name)
diff --git a/tests/Makefile.include b/tests/Makefile.include
index ea35cd54cc..9da831b882 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -388,6 +388,7 @@ qapi-schema += event-case.json
 qapi-schema += event-member-invalid-dict.json
 qapi-schema += event-nest-struct.json
 qapi-schema += features-bad-type.json
+qapi-schema += features-deprecated-type.json
 qapi-schema += features-duplicate-name.json
 qapi-schema += features-if-invalid.json
 qapi-schema += features-missing-name.json
diff --git a/tests/qapi-schema/features-deprecated-type.err b/tests/qapi-schema/features-deprecated-type.err
new file mode 100644
index 0000000000..af4ffe20aa
--- /dev/null
+++ b/tests/qapi-schema/features-deprecated-type.err
@@ -0,0 +1,2 @@
+features-deprecated-type.json: In struct 'S':
+features-deprecated-type.json:2: feature 'deprecated' is not supported for types
diff --git a/tests/qapi-schema/features-deprecated-type.json b/tests/qapi-schema/features-deprecated-type.json
new file mode 100644
index 0000000000..4b5bf5b86e
--- /dev/null
+++ b/tests/qapi-schema/features-deprecated-type.json
@@ -0,0 +1,3 @@
+# Feature 'deprecated' is not supported for types
+{ 'struct': 'S', 'data': {},
+  'features': [ 'deprecated' ] }
diff --git a/tests/qapi-schema/features-deprecated-type.out b/tests/qapi-schema/features-deprecated-type.out
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index fa4f3a15da..6862d8ba2c 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -308,7 +308,7 @@
   'features': [] }
 
 { 'command': 'test-command-features1',
-  'features': [ 'feature1' ] }
+  'features': [ 'deprecated' ] }
 { 'command': 'test-command-features3',
   'features': [ 'feature1', 'feature2' ] }
 
@@ -322,4 +322,4 @@
                                               'defined(TEST_IF_COND_2)'] } ] }
 
 { 'event': 'TEST-EVENT-FEATURES1',
-  'features': [ 'feature1' ] }
+  'features': [ 'deprecated' ] }
diff --git a/tests/qapi-schema/qapi-schema-test.out b/tests/qapi-schema/qapi-schema-test.out
index 1ece836d9b..494d4c25c4 100644
--- a/tests/qapi-schema/qapi-schema-test.out
+++ b/tests/qapi-schema/qapi-schema-test.out
@@ -432,7 +432,7 @@ command test-features0 q_obj_test-features0-arg -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
 command test-command-features1 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
-    feature feature1
+    feature deprecated
 command test-command-features3 None -> None
     gen=True success_response=True boxed=False oob=False preconfig=False
     feature feature1
@@ -453,4 +453,4 @@ command test-command-cond-features3 None -> None
         if ['defined(TEST_IF_COND_1)', 'defined(TEST_IF_COND_2)']
 event TEST-EVENT-FEATURES1 None
     boxed=False
-    feature feature1
+    feature deprecated
-- 
2.21.0