Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-08-26' into staging

QAPI patches patches for 2021-08-26

# gpg: Signature made Thu 26 Aug 2021 13:18:34 BST
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2021-08-26:
  qapi: make 'if' condition strings simple identifiers
  qapi: add 'not' condition operation
  qapi: Use 'if': { 'any': ... } where appropriate
  qapi: add 'any' condition
  qapi: replace if condition list with dict {'all': [...]}
  qapidoc: introduce QAPISchemaIfCond.docgen()
  qapi: introduce QAPISchemaIfCond.cgen()
  qapi: add QAPISchemaIfCond.is_present()
  qapi: wrap Sequence[str] in an object
  docs: update the documentation upfront about schema configuration
  qapi: Fix crash on redefinition with a different condition

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

9 files changed, 203 insertions, 126 deletions

diff --git a/scripts/qapi/commands.py b/scripts/qapi/commands.py
index 0e13d51054..3654825968 100644
--- a/scripts/qapi/commands.py
+++ b/scripts/qapi/commands.py
@@ -17,7 +17,6 @@ from typing import (
     Dict,
     List,
     Optional,
-    Sequence,
     Set,
 )
 
@@ -31,6 +30,7 @@ from .gen import (
 from .schema import (
     QAPISchema,
     QAPISchemaFeature,
+    QAPISchemaIfCond,
     QAPISchemaObjectType,
     QAPISchemaType,
 )
@@ -301,7 +301,7 @@ void %(c_prefix)sqmp_init_marshal(QmpCommandList *cmds)
     def visit_command(self,
                       name: str,
                       info: Optional[QAPISourceInfo],
-                      ifcond: Sequence[str],
+                      ifcond: QAPISchemaIfCond,
                       features: List[QAPISchemaFeature],
                       arg_type: Optional[QAPISchemaObjectType],
                       ret_type: Optional[QAPISchemaType],
diff --git a/scripts/qapi/common.py b/scripts/qapi/common.py
index 6ad1eeb61d..1724ac32db 100644
--- a/scripts/qapi/common.py
+++ b/scripts/qapi/common.py
@@ -12,7 +12,13 @@
 # See the COPYING file in the top-level directory.
 
 import re
-from typing import Match, Optional, Sequence
+from typing import (
+    Any,
+    Dict,
+    Match,
+    Optional,
+    Union,
+)
 
 
 #: Magic string that gets removed along with all space to its right.
@@ -194,22 +200,49 @@ def guardend(name: str) -> str:
                  name=c_fname(name).upper())
 
 
-def gen_if(ifcond: Sequence[str]) -> str:
-    ret = ''
-    for ifc in ifcond:
-        ret += mcgen('''
+def cgen_ifcond(ifcond: Union[str, Dict[str, Any]]) -> str:
+    if not ifcond:
+        return ''
+    if isinstance(ifcond, str):
+        return 'defined(' + ifcond + ')'
+
+    oper, operands = next(iter(ifcond.items()))
+    if oper == 'not':
+        return '!' + cgen_ifcond(operands)
+    oper = {'all': '&&', 'any': '||'}[oper]
+    operands = [cgen_ifcond(o) for o in operands]
+    return '(' + (') ' + oper + ' (').join(operands) + ')'
+
+
+def docgen_ifcond(ifcond: Union[str, Dict[str, Any]]) -> str:
+    # TODO Doc generated for conditions needs polish
+    if not ifcond:
+        return ''
+    if isinstance(ifcond, str):
+        return ifcond
+
+    oper, operands = next(iter(ifcond.items()))
+    if oper == 'not':
+        return '!' + docgen_ifcond(operands)
+    oper = {'all': ' and ', 'any': ' or '}[oper]
+    operands = [docgen_ifcond(o) for o in operands]
+    return '(' + oper.join(operands) + ')'
+
+
+def gen_if(cond: str) -> str:
+    if not cond:
+        return ''
+    return mcgen('''
 #if %(cond)s
-''', cond=ifc)
-    return ret
+''', cond=cond)
 
 
-def gen_endif(ifcond: Sequence[str]) -> str:
-    ret = ''
-    for ifc in reversed(ifcond):
-        ret += mcgen('''
+def gen_endif(cond: str) -> str:
+    if not cond:
+        return ''
+    return mcgen('''
 #endif /* %(cond)s */
-''', cond=ifc)
-    return ret
+''', cond=cond)
 
 
 def must_match(pattern: str, string: str) -> Match[str]:
diff --git a/scripts/qapi/events.py b/scripts/qapi/events.py
index fee8c671e7..82475e84ec 100644
--- a/scripts/qapi/events.py
+++ b/scripts/qapi/events.py
@@ -12,7 +12,7 @@ This work is licensed under the terms of the GNU GPL, version 2.
 See the COPYING file in the top-level directory.
 """
 
-from typing import List, Optional, Sequence
+from typing import List, Optional
 
 from .common import c_enum_const, c_name, mcgen
 from .gen import QAPISchemaModularCVisitor, build_params, ifcontext
@@ -20,6 +20,7 @@ from .schema import (
     QAPISchema,
     QAPISchemaEnumMember,
     QAPISchemaFeature,
+    QAPISchemaIfCond,
     QAPISchemaObjectType,
 )
 from .source import QAPISourceInfo
@@ -227,7 +228,7 @@ void %(event_emit)s(%(event_enum)s event, QDict *qdict);
     def visit_event(self,
                     name: str,
                     info: Optional[QAPISourceInfo],
-                    ifcond: Sequence[str],
+                    ifcond: QAPISchemaIfCond,
                     features: List[QAPISchemaFeature],
                     arg_type: Optional[QAPISchemaObjectType],
                     boxed: bool) -> None:
diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
index cf98923fa6..019f4c97aa 100644
--- a/scripts/qapi/expr.py
+++ b/scripts/qapi/expr.py
@@ -259,14 +259,9 @@ def check_flags(expr: _JSONObject, info: QAPISourceInfo) -> None:
 
 def check_if(expr: _JSONObject, info: QAPISourceInfo, source: str) -> None:
     """
-    Normalize and validate the ``if`` member of an object.
+    Validate the ``if`` member of an object.
 
-    The ``if`` member may be either a ``str`` or a ``List[str]``.
-    A ``str`` value will be normalized to ``List[str]``.
-
-    :forms:
-      :sugared: ``Union[str, List[str]]``
-      :canonical: ``List[str]``
+    The ``if`` member may be either a ``str`` or a dict.
 
     :param expr: The expression containing the ``if`` member to validate.
     :param info: QAPI schema source file information.
@@ -275,31 +270,49 @@ def check_if(expr: _JSONObject, info: QAPISourceInfo, source: str) -> None:
     :raise QAPISemError:
         When the "if" member fails validation, or when there are no
         non-empty conditions.
-    :return: None, ``expr`` is normalized in-place as needed.
+    :return: None
     """
-    ifcond = expr.get('if')
-    if ifcond is None:
-        return
 
-    if isinstance(ifcond, list):
-        if not ifcond:
-            raise QAPISemError(
-                info, "'if' condition [] of %s is useless" % source)
-    else:
-        # Normalize to a list
-        ifcond = expr['if'] = [ifcond]
+    def _check_if(cond: Union[str, object]) -> None:
+        if isinstance(cond, str):
+            if not re.match(r'^[A-Z][A-Z0-9_]*$', cond):
+                raise QAPISemError(
+                    info,
+                    "'if' condition '%s' of %s is not a valid identifier"
+                    % (cond, source))
+            return
 
-    for elt in ifcond:
-        if not isinstance(elt, str):
+        if not isinstance(cond, dict):
             raise QAPISemError(
                 info,
-                "'if' condition of %s must be a string or a list of strings"
-                % source)
-        if not elt.strip():
+                "'if' condition of %s must be a string or an object" % source)
+        if len(cond) != 1:
             raise QAPISemError(
                 info,
-                "'if' condition '%s' of %s makes no sense"
-                % (elt, source))
+                "'if' condition dict of %s must have one key: "
+                "'all', 'any' or 'not'" % source)
+        check_keys(cond, info, "'if' condition", [],
+                   ["all", "any", "not"])
+
+        oper, operands = next(iter(cond.items()))
+        if not operands:
+            raise QAPISemError(
+                info, "'if' condition [] of %s is useless" % source)
+
+        if oper == "not":
+            _check_if(operands)
+            return
+        if oper in ("all", "any") and not isinstance(operands, list):
+            raise QAPISemError(
+                info, "'%s' condition of %s must be an array" % (oper, source))
+        for operand in operands:
+            _check_if(operand)
+
+    ifcond = expr.get('if')
+    if ifcond is None:
+        return
+
+    _check_if(ifcond)
 
 
 def normalize_members(members: object) -> None:
diff --git a/scripts/qapi/gen.py b/scripts/qapi/gen.py
index 1fa503bdbd..51a597a025 100644
--- a/scripts/qapi/gen.py
+++ b/scripts/qapi/gen.py
@@ -18,7 +18,6 @@ from typing import (
     Dict,
     Iterator,
     Optional,
-    Sequence,
     Tuple,
 )
 
@@ -32,6 +31,7 @@ from .common import (
     mcgen,
 )
 from .schema import (
+    QAPISchemaIfCond,
     QAPISchemaModule,
     QAPISchemaObjectType,
     QAPISchemaVisitor,
@@ -85,7 +85,7 @@ class QAPIGen:
                 fp.write(text)
 
 
-def _wrap_ifcond(ifcond: Sequence[str], before: str, after: str) -> str:
+def _wrap_ifcond(ifcond: QAPISchemaIfCond, before: str, after: str) -> str:
     if before == after:
         return after   # suppress empty #if ... #endif
 
@@ -95,9 +95,9 @@ def _wrap_ifcond(ifcond: Sequence[str], before: str, after: str) -> str:
     if added[0] == '\n':
         out += '\n'
         added = added[1:]
-    out += gen_if(ifcond)
+    out += gen_if(ifcond.cgen())
     out += added
-    out += gen_endif(ifcond)
+    out += gen_endif(ifcond.cgen())
     return out
 
 
@@ -127,9 +127,9 @@ def build_params(arg_type: Optional[QAPISchemaObjectType],
 class QAPIGenCCode(QAPIGen):
     def __init__(self, fname: str):
         super().__init__(fname)
-        self._start_if: Optional[Tuple[Sequence[str], str, str]] = None
+        self._start_if: Optional[Tuple[QAPISchemaIfCond, str, str]] = None
 
-    def start_if(self, ifcond: Sequence[str]) -> None:
+    def start_if(self, ifcond: QAPISchemaIfCond) -> None:
         assert self._start_if is None
         self._start_if = (ifcond, self._body, self._preamble)
 
@@ -187,7 +187,7 @@ class QAPIGenH(QAPIGenC):
 
 
 @contextmanager
-def ifcontext(ifcond: Sequence[str], *args: QAPIGenCCode) -> Iterator[None]:
+def ifcontext(ifcond: QAPISchemaIfCond, *args: QAPIGenCCode) -> Iterator[None]:
     """
     A with-statement context manager that wraps with `start_if()` / `end_if()`.
 
diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index 9a348ca2e5..bd4233ecee 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -15,11 +15,9 @@ from typing import (
     Any,
     Dict,
     Generic,
-    Iterable,
     List,
     Optional,
     Sequence,
-    Tuple,
     TypeVar,
     Union,
 )
@@ -38,6 +36,7 @@ from .schema import (
     QAPISchemaEntity,
     QAPISchemaEnumMember,
     QAPISchemaFeature,
+    QAPISchemaIfCond,
     QAPISchemaObjectType,
     QAPISchemaObjectTypeMember,
     QAPISchemaType,
@@ -91,11 +90,11 @@ class Annotated(Generic[_ValueT]):
     """
     # TODO: Remove after Python 3.7 adds @dataclass:
     # pylint: disable=too-few-public-methods
-    def __init__(self, value: _ValueT, ifcond: Iterable[str],
+    def __init__(self, value: _ValueT, ifcond: QAPISchemaIfCond,
                  comment: Optional[str] = None):
         self.value = value
         self.comment: Optional[str] = comment
-        self.ifcond: Tuple[str, ...] = tuple(ifcond)
+        self.ifcond = ifcond
 
 
 def _tree_to_qlit(obj: JSONValue,
@@ -124,11 +123,11 @@ def _tree_to_qlit(obj: JSONValue,
         ret = ''
         if obj.comment:
             ret += indent(level) + f"/* {obj.comment} */\n"
-        if obj.ifcond:
-            ret += gen_if(obj.ifcond)
+        if obj.ifcond.is_present():
+            ret += gen_if(obj.ifcond.cgen())
         ret += _tree_to_qlit(obj.value, level)
-        if obj.ifcond:
-            ret += '\n' + gen_endif(obj.ifcond)
+        if obj.ifcond.is_present():
+            ret += '\n' + gen_endif(obj.ifcond.cgen())
         return ret
 
     ret = ''
@@ -254,7 +253,7 @@ const QLitObject %(c_name)s = %(c_string)s;
         return [Annotated(f.name, f.ifcond) for f in features]
 
     def _gen_tree(self, name: str, mtype: str, obj: Dict[str, object],
-                  ifcond: Sequence[str] = (),
+                  ifcond: QAPISchemaIfCond = QAPISchemaIfCond(),
                   features: Sequence[QAPISchemaFeature] = ()) -> None:
         """
         Build and append a SchemaInfo object to self._trees.
@@ -305,7 +304,7 @@ const QLitObject %(c_name)s = %(c_string)s;
         self._gen_tree(name, 'builtin', {'json-type': json_type})
 
     def visit_enum_type(self, name: str, info: Optional[QAPISourceInfo],
-                        ifcond: Sequence[str],
+                        ifcond: QAPISchemaIfCond,
                         features: List[QAPISchemaFeature],
                         members: List[QAPISchemaEnumMember],
                         prefix: Optional[str]) -> None:
@@ -316,14 +315,14 @@ const QLitObject %(c_name)s = %(c_string)s;
         )
 
     def visit_array_type(self, name: str, info: Optional[QAPISourceInfo],
-                         ifcond: Sequence[str],
+                         ifcond: QAPISchemaIfCond,
                          element_type: QAPISchemaType) -> None:
         element = self._use_type(element_type)
         self._gen_tree('[' + element + ']', 'array', {'element-type': element},
                        ifcond)
 
     def visit_object_type_flat(self, name: str, info: Optional[QAPISourceInfo],
-                               ifcond: Sequence[str],
+                               ifcond: QAPISchemaIfCond,
                                features: List[QAPISchemaFeature],
                                members: List[QAPISchemaObjectTypeMember],
                                variants: Optional[QAPISchemaVariants]) -> None:
@@ -336,7 +335,7 @@ const QLitObject %(c_name)s = %(c_string)s;
         self._gen_tree(name, 'object', obj, ifcond, features)
 
     def visit_alternate_type(self, name: str, info: Optional[QAPISourceInfo],
-                             ifcond: Sequence[str],
+                             ifcond: QAPISchemaIfCond,
                              features: List[QAPISchemaFeature],
                              variants: QAPISchemaVariants) -> None:
         self._gen_tree(
@@ -348,7 +347,7 @@ const QLitObject %(c_name)s = %(c_string)s;
         )
 
     def visit_command(self, name: str, info: Optional[QAPISourceInfo],
-                      ifcond: Sequence[str],
+                      ifcond: QAPISchemaIfCond,
                       features: List[QAPISchemaFeature],
                       arg_type: Optional[QAPISchemaObjectType],
                       ret_type: Optional[QAPISchemaType], gen: bool,
@@ -367,7 +366,8 @@ const QLitObject %(c_name)s = %(c_string)s;
         self._gen_tree(name, 'command', obj, ifcond, features)
 
     def visit_event(self, name: str, info: Optional[QAPISourceInfo],
-                    ifcond: Sequence[str], features: List[QAPISchemaFeature],
+                    ifcond: QAPISchemaIfCond,
+                    features: List[QAPISchemaFeature],
                     arg_type: Optional[QAPISchemaObjectType],
                     boxed: bool) -> None:
         assert self._schema is not None
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index d1d27ff7ee..229d24fce9 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -19,12 +19,31 @@ import os
 import re
 from typing import Optional
 
-from .common import POINTER_SUFFIX, c_name
+from .common import (
+    POINTER_SUFFIX,
+    c_name,
+    cgen_ifcond,
+    docgen_ifcond,
+)
 from .error import QAPIError, QAPISemError, QAPISourceError
 from .expr import check_exprs
 from .parser import QAPISchemaParser
 
 
+class QAPISchemaIfCond:
+    def __init__(self, ifcond=None):
+        self.ifcond = ifcond or {}
+
+    def cgen(self):
+        return cgen_ifcond(self.ifcond)
+
+    def docgen(self):
+        return docgen_ifcond(self.ifcond)
+
+    def is_present(self):
+        return bool(self.ifcond)
+
+
 class QAPISchemaEntity:
     meta: Optional[str] = None
 
@@ -42,7 +61,7 @@ class QAPISchemaEntity:
         # such place).
         self.info = info
         self.doc = doc
-        self._ifcond = ifcond or []
+        self._ifcond = ifcond or QAPISchemaIfCond()
         self.features = features or []
         self._checked = False
 
@@ -593,7 +612,7 @@ class QAPISchemaVariants:
                     self.info,
                     "discriminator member '%s' of %s must not be optional"
                     % (self._tag_name, base))
-            if self.tag_member.ifcond:
+            if self.tag_member.ifcond.is_present():
                 raise QAPISemError(
                     self.info,
                     "discriminator member '%s' of %s must not be conditional"
@@ -601,7 +620,7 @@ class QAPISchemaVariants:
         else:                   # simple union
             assert isinstance(self.tag_member.type, QAPISchemaEnumType)
             assert not self.tag_member.optional
-            assert self.tag_member.ifcond == []
+            assert not self.tag_member.ifcond.is_present()
         if self._tag_name:    # flat union
             # branches that are not explicitly covered get an empty type
             cases = {v.name for v in self.variants}
@@ -646,7 +665,7 @@ class QAPISchemaMember:
         assert isinstance(name, str)
         self.name = name
         self.info = info
-        self.ifcond = ifcond or []
+        self.ifcond = ifcond or QAPISchemaIfCond()
         self.defined_in = None
 
     def set_defined_in(self, name):
@@ -968,11 +987,13 @@ class QAPISchema:
     def _make_features(self, features, info):
         if features is None:
             return []
-        return [QAPISchemaFeature(f['name'], info, f.get('if'))
+        return [QAPISchemaFeature(f['name'], info,
+                                  QAPISchemaIfCond(f.get('if')))
                 for f in features]
 
     def _make_enum_members(self, values, info):
-        return [QAPISchemaEnumMember(v['name'], info, v.get('if'))
+        return [QAPISchemaEnumMember(v['name'], info,
+                                     QAPISchemaIfCond(v.get('if')))
                 for v in values]
 
     def _make_implicit_enum_type(self, name, info, ifcond, values):
@@ -997,18 +1018,18 @@ class QAPISchema:
         name = 'q_obj_%s-%s' % (name, role)
         typ = self.lookup_entity(name, QAPISchemaObjectType)
         if typ:
-            # The implicit object type has multiple users.  This can
-            # happen only for simple unions' implicit wrapper types.
-            # Its ifcond should be the disjunction of its user's
-            # ifconds.  Not implemented.  Instead, we always pass the
-            # wrapped type's ifcond, which is trivially the same for all
-            # users.  It's also necessary for the wrapper to compile.
-            # But it's not tight: the disjunction need not imply it.  We
-            # may end up compiling useless wrapper types.
+            # The implicit object type has multiple users.  This is
+            # either a duplicate definition (which will be flagged
+            # later), or an implicit wrapper type used for multiple
+            # simple unions.  In the latter case, ifcond should be the
+            # disjunction of its user's ifconds.  Not implemented.
+            # Instead, we always pass the wrapped type's ifcond, which
+            # is trivially the same for all users.  It's also
+            # necessary for the wrapper to compile.  But it's not
+            # tight: the disjunction need not imply it.  We may end up
+            # compiling useless wrapper types.
             # TODO kill simple unions or implement the disjunction
-
-            # pylint: disable=protected-access
-            assert (ifcond or []) == typ._ifcond
+            pass
         else:
             self._def_entity(QAPISchemaObjectType(
                 name, info, None, ifcond, None, None, members, None))
@@ -1018,7 +1039,7 @@ class QAPISchema:
         name = expr['enum']
         data = expr['data']
         prefix = expr.get('prefix')
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
         self._def_entity(QAPISchemaEnumType(
             name, info, doc, ifcond, features,
@@ -1036,7 +1057,8 @@ class QAPISchema:
                                           self._make_features(features, info))
 
     def _make_members(self, data, info):
-        return [self._make_member(key, value['type'], value.get('if'),
+        return [self._make_member(key, value['type'],
+                                  QAPISchemaIfCond(value.get('if')),
                                   value.get('features'), info)
                 for (key, value) in data.items()]
 
@@ -1044,7 +1066,7 @@ class QAPISchema:
         name = expr['struct']
         base = expr.get('base')
         data = expr['data']
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
         self._def_entity(QAPISchemaObjectType(
             name, info, doc, ifcond, features, base,
@@ -1067,7 +1089,7 @@ class QAPISchema:
         name = expr['union']
         data = expr['data']
         base = expr.get('base')
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
         tag_name = expr.get('discriminator')
         tag_member = None
@@ -1076,15 +1098,19 @@ class QAPISchema:
                 name, info, ifcond,
                 'base', self._make_members(base, info))
         if tag_name:
-            variants = [self._make_variant(key, value['type'],
-                                           value.get('if'), info)
-                        for (key, value) in data.items()]
+            variants = [
+                self._make_variant(key, value['type'],
+                                   QAPISchemaIfCond(value.get('if')),
+                                   info)
+                for (key, value) in data.items()]
             members = []
         else:
-            variants = [self._make_simple_variant(key, value['type'],
-                                                  value.get('if'), info)
-                        for (key, value) in data.items()]
-            enum = [{'name': v.name, 'if': v.ifcond} for v in variants]
+            variants = [
+                self._make_simple_variant(key, value['type'],
+                                          QAPISchemaIfCond(value.get('if')),
+                                          info)
+                for (key, value) in data.items()]
+            enum = [{'name': v.name, 'if': v.ifcond.ifcond} for v in variants]
             typ = self._make_implicit_enum_type(name, info, ifcond, enum)
             tag_member = QAPISchemaObjectTypeMember('type', info, typ, False)
             members = [tag_member]
@@ -1097,11 +1123,13 @@ class QAPISchema:
     def _def_alternate_type(self, expr, info, doc):
         name = expr['alternate']
         data = expr['data']
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
-        variants = [self._make_variant(key, value['type'], value.get('if'),
-                                       info)
-                    for (key, value) in data.items()]
+        variants = [
+            self._make_variant(key, value['type'],
+                               QAPISchemaIfCond(value.get('if')),
+                               info)
+            for (key, value) in data.items()]
         tag_member = QAPISchemaObjectTypeMember('type', info, 'QType', False)
         self._def_entity(
             QAPISchemaAlternateType(name, info, doc, ifcond, features,
@@ -1118,7 +1146,7 @@ class QAPISchema:
         allow_oob = expr.get('allow-oob', False)
         allow_preconfig = expr.get('allow-preconfig', False)
         coroutine = expr.get('coroutine', False)
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
         if isinstance(data, OrderedDict):
             data = self._make_implicit_object_type(
@@ -1137,7 +1165,7 @@ class QAPISchema:
         name = expr['event']
         data = expr.get('data')
         boxed = expr.get('boxed', False)
-        ifcond = expr.get('if')
+        ifcond = QAPISchemaIfCond(expr.get('if'))
         features = self._make_features(expr.get('features'), info)
         if isinstance(data, OrderedDict):
             data = self._make_implicit_object_type(
diff --git a/scripts/qapi/types.py b/scripts/qapi/types.py
index 20d572a23a..db9ff95bd1 100644
--- a/scripts/qapi/types.py
+++ b/scripts/qapi/types.py
@@ -13,7 +13,7 @@ This work is licensed under the terms of the GNU GPL, version 2.
 # See the COPYING file in the top-level directory.
 """
 
-from typing import List, Optional, Sequence
+from typing import List, Optional
 
 from .common import (
     c_enum_const,
@@ -27,6 +27,7 @@ from .schema import (
     QAPISchema,
     QAPISchemaEnumMember,
     QAPISchemaFeature,
+    QAPISchemaIfCond,
     QAPISchemaObjectType,
     QAPISchemaObjectTypeMember,
     QAPISchemaType,
@@ -50,13 +51,13 @@ const QEnumLookup %(c_name)s_lookup = {
 ''',
                 c_name=c_name(name))
     for memb in members:
-        ret += gen_if(memb.ifcond)
+        ret += gen_if(memb.ifcond.cgen())
         index = c_enum_const(name, memb.name, prefix)
         ret += mcgen('''
         [%(index)s] = "%(name)s",
 ''',
                      index=index, name=memb.name)
-        ret += gen_endif(memb.ifcond)
+        ret += gen_endif(memb.ifcond.cgen())
 
     ret += mcgen('''
     },
@@ -80,12 +81,12 @@ typedef enum %(c_name)s {
                 c_name=c_name(name))
 
     for memb in enum_members:
-        ret += gen_if(memb.ifcond)
+        ret += gen_if(memb.ifcond.cgen())
         ret += mcgen('''
     %(c_enum)s,
 ''',
                      c_enum=c_enum_const(name, memb.name, prefix))
-        ret += gen_endif(memb.ifcond)
+        ret += gen_endif(memb.ifcond.cgen())
 
     ret += mcgen('''
 } %(c_name)s;
@@ -125,7 +126,7 @@ struct %(c_name)s {
 def gen_struct_members(members: List[QAPISchemaObjectTypeMember]) -> str:
     ret = ''
     for memb in members:
-        ret += gen_if(memb.ifcond)
+        ret += gen_if(memb.ifcond.cgen())
         if memb.optional:
             ret += mcgen('''
     bool has_%(c_name)s;
@@ -135,11 +136,11 @@ def gen_struct_members(members: List[QAPISchemaObjectTypeMember]) -> str:
     %(c_type)s %(c_name)s;
 ''',
                      c_type=memb.type.c_type(), c_name=c_name(memb.name))
-        ret += gen_endif(memb.ifcond)
+        ret += gen_endif(memb.ifcond.cgen())
     return ret
 
 
-def gen_object(name: str, ifcond: Sequence[str],
+def gen_object(name: str, ifcond: QAPISchemaIfCond,
                base: Optional[QAPISchemaObjectType],
                members: List[QAPISchemaObjectTypeMember],
                variants: Optional[QAPISchemaVariants]) -> str:
@@ -158,7 +159,7 @@ def gen_object(name: str, ifcond: Sequence[str],
     ret += mcgen('''
 
 ''')
-    ret += gen_if(ifcond)
+    ret += gen_if(ifcond.cgen())
     ret += mcgen('''
 struct %(c_name)s {
 ''',
@@ -192,7 +193,7 @@ struct %(c_name)s {
     ret += mcgen('''
 };
 ''')
-    ret += gen_endif(ifcond)
+    ret += gen_endif(ifcond.cgen())
 
     return ret
 
@@ -219,13 +220,13 @@ def gen_variants(variants: QAPISchemaVariants) -> str:
     for var in variants.variants:
         if var.type.name == 'q_empty':
             continue
-        ret += gen_if(var.ifcond)
+        ret += gen_if(var.ifcond.cgen())
         ret += mcgen('''
         %(c_type)s %(c_name)s;
 ''',
                      c_type=var.type.c_unboxed_type(),
                      c_name=c_name(var.name))
-        ret += gen_endif(var.ifcond)
+        ret += gen_endif(var.ifcond.cgen())
 
     ret += mcgen('''
     } u;
@@ -307,7 +308,7 @@ class QAPISchemaGenTypeVisitor(QAPISchemaModularCVisitor):
     def visit_enum_type(self,
                         name: str,
                         info: Optional[QAPISourceInfo],
-                        ifcond: Sequence[str],
+                        ifcond: QAPISchemaIfCond,
                         features: List[QAPISchemaFeature],
                         members: List[QAPISchemaEnumMember],
                         prefix: Optional[str]) -> None:
@@ -318,7 +319,7 @@ class QAPISchemaGenTypeVisitor(QAPISchemaModularCVisitor):
     def visit_array_type(self,
                          name: str,
                          info: Optional[QAPISourceInfo],
-                         ifcond: Sequence[str],
+                         ifcond: QAPISchemaIfCond,
                          element_type: QAPISchemaType) -> None:
         with ifcontext(ifcond, self._genh, self._genc):
             self._genh.preamble_add(gen_fwd_object_or_array(name))
@@ -328,7 +329,7 @@ class QAPISchemaGenTypeVisitor(QAPISchemaModularCVisitor):
     def visit_object_type(self,
                           name: str,
                           info: Optional[QAPISourceInfo],
-                          ifcond: Sequence[str],
+                          ifcond: QAPISchemaIfCond,
                           features: List[QAPISchemaFeature],
                           base: Optional[QAPISchemaObjectType],
                           members: List[QAPISchemaObjectTypeMember],
@@ -351,7 +352,7 @@ class QAPISchemaGenTypeVisitor(QAPISchemaModularCVisitor):
     def visit_alternate_type(self,
                              name: str,
                              info: Optional[QAPISourceInfo],
-                             ifcond: Sequence[str],
+                             ifcond: QAPISchemaIfCond,
                              features: List[QAPISchemaFeature],
                              variants: QAPISchemaVariants) -> None:
         with ifcontext(ifcond, self._genh):
diff --git a/scripts/qapi/visit.py b/scripts/qapi/visit.py
index 9e96f3c566..56ea516399 100644
--- a/scripts/qapi/visit.py
+++ b/scripts/qapi/visit.py
@@ -13,7 +13,7 @@ This work is licensed under the terms of the GNU GPL, version 2.
 See the COPYING file in the top-level directory.
 """
 
-from typing import List, Optional, Sequence
+from typing import List, Optional
 
 from .common import (
     c_enum_const,
@@ -29,6 +29,7 @@ from .schema import (
     QAPISchemaEnumMember,
     QAPISchemaEnumType,
     QAPISchemaFeature,
+    QAPISchemaIfCond,
     QAPISchemaObjectType,
     QAPISchemaObjectTypeMember,
     QAPISchemaType,
@@ -78,7 +79,7 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
 
     for memb in members:
         deprecated = 'deprecated' in [f.name for f in memb.features]
-        ret += gen_if(memb.ifcond)
+        ret += gen_if(memb.ifcond.cgen())
         if memb.optional:
             ret += mcgen('''
     if (visit_optional(v, "%(name)s", &obj->has_%(c_name)s)) {
@@ -111,7 +112,7 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
             ret += mcgen('''
     }
 ''')
-        ret += gen_endif(memb.ifcond)
+        ret += gen_endif(memb.ifcond.cgen())
 
     if variants:
         tag_member = variants.tag_member
@@ -125,7 +126,7 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
         for var in variants.variants:
             case_str = c_enum_const(tag_member.type.name, var.name,
                                     tag_member.type.prefix)
-            ret += gen_if(var.ifcond)
+            ret += gen_if(var.ifcond.cgen())
             if var.type.name == 'q_empty':
                 # valid variant and nothing to do
                 ret += mcgen('''
@@ -141,7 +142,7 @@ bool visit_type_%(c_name)s_members(Visitor *v, %(c_name)s *obj, Error **errp)
                              case=case_str,
                              c_type=var.type.c_name(), c_name=c_name(var.name))
 
-            ret += gen_endif(var.ifcond)
+            ret += gen_endif(var.ifcond.cgen())
         ret += mcgen('''
     default:
         abort();
@@ -227,7 +228,7 @@ bool visit_type_%(c_name)s(Visitor *v, const char *name,
                 c_name=c_name(name))
 
     for var in variants.variants:
-        ret += gen_if(var.ifcond)
+        ret += gen_if(var.ifcond.cgen())
         ret += mcgen('''
     case %(case)s:
 ''',
@@ -253,7 +254,7 @@ bool visit_type_%(c_name)s(Visitor *v, const char *name,
         ret += mcgen('''
         break;
 ''')
-        ret += gen_endif(var.ifcond)
+        ret += gen_endif(var.ifcond.cgen())
 
     ret += mcgen('''
     case QTYPE_NONE:
@@ -352,7 +353,7 @@ class QAPISchemaGenVisitVisitor(QAPISchemaModularCVisitor):
     def visit_enum_type(self,
                         name: str,
                         info: Optional[QAPISourceInfo],
-                        ifcond: Sequence[str],
+                        ifcond: QAPISchemaIfCond,
                         features: List[QAPISchemaFeature],
                         members: List[QAPISchemaEnumMember],
                         prefix: Optional[str]) -> None:
@@ -363,7 +364,7 @@ class QAPISchemaGenVisitVisitor(QAPISchemaModularCVisitor):
     def visit_array_type(self,
                          name: str,
                          info: Optional[QAPISourceInfo],
-                         ifcond: Sequence[str],
+                         ifcond: QAPISchemaIfCond,
                          element_type: QAPISchemaType) -> None:
         with ifcontext(ifcond, self._genh, self._genc):
             self._genh.add(gen_visit_decl(name))
@@ -372,7 +373,7 @@ class QAPISchemaGenVisitVisitor(QAPISchemaModularCVisitor):
     def visit_object_type(self,
                           name: str,
                           info: Optional[QAPISourceInfo],
-                          ifcond: Sequence[str],
+                          ifcond: QAPISchemaIfCond,
                           features: List[QAPISchemaFeature],
                           base: Optional[QAPISchemaObjectType],
                           members: List[QAPISchemaObjectTypeMember],
@@ -394,7 +395,7 @@ class QAPISchemaGenVisitVisitor(QAPISchemaModularCVisitor):
     def visit_alternate_type(self,
                              name: str,
                              info: Optional[QAPISourceInfo],
-                             ifcond: Sequence[str],
+                             ifcond: QAPISchemaIfCond,
                              features: List[QAPISchemaFeature],
                              variants: QAPISchemaVariants) -> None:
         with ifcontext(ifcond, self._genh, self._genc):