qapi: New QAPISchema intermediate reperesentation

The QAPI code generators work with a syntax tree (nested dictionaries)
plus a few symbol tables (also dictionaries) on the side.

They have clearly outgrown these simple data structures.  There's lots
of rummaging around in dictionaries, and information is recomputed on
the fly.  For the work I'm going to do, I want more clearly defined
and more convenient interfaces.

Going forward, I also want less coupling between the back-ends and the
syntax tree, to make messing with the syntax easier.

Create a bunch of classes to represent QAPI schemata.

Have the QAPISchema initializer call the parser, then walk the syntax
tree to create the new internal representation, and finally perform
semantic analysis.

Shortcut: the semantic analysis still relies on existing check_exprs()
to do the actual semantic checking.  All this code needs to move into
the classes.  Mark as TODO.

Simple unions are lowered to flat unions.  Flat unions and structs are
represented as a more general object type.

Catching name collisions in generated code would be nice.  Mark as
TODO.

We generate array types eagerly, even though most of them aren't used.
Mark as TODO.

Nothing uses the new intermediate representation just yet, thus no
change to generated files.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

scripts/qapi-commands.py

@@ -272,7 +272,7 @@ for o, a in opts:
     if o in ("-m", "--middle"):
         middle_mode = True
 
-exprs = parse_schema(input_file)
+exprs = QAPISchema(input_file).get_exprs()
 commands = filter(lambda expr: expr.has_key('command'), exprs)
 commands = filter(lambda expr: not expr.has_key('gen'), commands)
 

scripts/qapi-event.py

@@ -263,7 +263,7 @@ fdecl.write(mcgen('''
 ''',
                   prefix=prefix))
 
-exprs = parse_schema(input_file)
+exprs = QAPISchema(input_file).get_exprs()
 
 event_enum_name = c_name(prefix + "QAPIEvent", protect=False)
 event_enum_values = []

scripts/qapi-types.py

@@ -336,7 +336,7 @@ fdecl.write(mcgen('''
 #include <stdint.h>
 '''))
 
-exprs = parse_schema(input_file)
+exprs = QAPISchema(input_file).get_exprs()
 
 fdecl.write(guardstart("QAPI_TYPES_BUILTIN_STRUCT_DECL"))
 for typename in builtin_types.keys():

scripts/qapi-visit.py

@@ -446,7 +446,7 @@ fdecl.write(mcgen('''
 ''',
                   prefix=prefix))
 
-exprs = parse_schema(input_file)
+exprs = QAPISchema(input_file).get_exprs()
 
 # to avoid header dependency hell, we always generate declarations
 # for built-in types in our header files and simply guard them

scripts/qapi.py

@@ -302,6 +302,8 @@ class QAPISchemaParser(object):
 
 #
 # Semantic analysis of schema expressions
+# TODO fold into QAPISchema
+# TODO catching name collisions in generated code would be nice
 #
 
 def find_base_fields(base):
@@ -751,15 +753,377 @@ def check_exprs(exprs):
         else:
             assert False, 'unexpected meta type'
 
-    return map(lambda expr_elem: expr_elem['expr'], exprs)
+    return exprs
+
+
+#
+# Schema compiler frontend
+#
+
+class QAPISchemaEntity(object):
+    def __init__(self, name, info):
+        assert isinstance(name, str)
+        self.name = name
+        self.info = info
+
+    def check(self, schema):
+        pass
+
+
+class QAPISchemaType(QAPISchemaEntity):
+    pass
+
+
+class QAPISchemaBuiltinType(QAPISchemaType):
+    def __init__(self, name):
+        QAPISchemaType.__init__(self, name, None)
+
+
+class QAPISchemaEnumType(QAPISchemaType):
+    def __init__(self, name, info, values, prefix):
+        QAPISchemaType.__init__(self, name, info)
+        for v in values:
+            assert isinstance(v, str)
+        assert prefix is None or isinstance(prefix, str)
+        self.values = values
+        self.prefix = prefix
+
+    def check(self, schema):
+        assert len(set(self.values)) == len(self.values)
+
+
+class QAPISchemaArrayType(QAPISchemaType):
+    def __init__(self, name, info, element_type):
+        QAPISchemaType.__init__(self, name, info)
+        assert isinstance(element_type, str)
+        self._element_type_name = element_type
+        self.element_type = None
+
+    def check(self, schema):
+        self.element_type = schema.lookup_type(self._element_type_name)
+        assert self.element_type
+
+
+class QAPISchemaObjectType(QAPISchemaType):
+    def __init__(self, name, info, base, local_members, variants):
+        QAPISchemaType.__init__(self, name, info)
+        assert base is None or isinstance(base, str)
+        for m in local_members:
+            assert isinstance(m, QAPISchemaObjectTypeMember)
+        assert (variants is None or
+                isinstance(variants, QAPISchemaObjectTypeVariants))
+        self._base_name = base
+        self.base = None
+        self.local_members = local_members
+        self.variants = variants
+        self.members = None
+
+    def check(self, schema):
+        assert self.members is not False        # not running in cycles
+        if self.members:
+            return
+        self.members = False                    # mark as being checked
+        if self._base_name:
+            self.base = schema.lookup_type(self._base_name)
+            assert isinstance(self.base, QAPISchemaObjectType)
+            assert not self.base.variants       # not implemented
+            self.base.check(schema)
+            members = list(self.base.members)
+        else:
+            members = []
+        seen = {}
+        for m in members:
+            seen[m.name] = m
+        for m in self.local_members:
+            m.check(schema, members, seen)
+        if self.variants:
+            self.variants.check(schema, members, seen)
+        self.members = members
+
+
+class QAPISchemaObjectTypeMember(object):
+    def __init__(self, name, typ, optional):
+        assert isinstance(name, str)
+        assert isinstance(typ, str)
+        assert isinstance(optional, bool)
+        self.name = name
+        self._type_name = typ
+        self.type = None
+        self.optional = optional
+
+    def check(self, schema, all_members, seen):
+        assert self.name not in seen
+        self.type = schema.lookup_type(self._type_name)
+        assert self.type
+        all_members.append(self)
+        seen[self.name] = self
+
+
+class QAPISchemaObjectTypeVariants(object):
+    def __init__(self, tag_name, tag_enum, variants):
+        assert tag_name is None or isinstance(tag_name, str)
+        assert tag_enum is None or isinstance(tag_enum, str)
+        for v in variants:
+            assert isinstance(v, QAPISchemaObjectTypeVariant)
+        self.tag_name = tag_name
+        if tag_name:
+            assert not tag_enum
+            self.tag_member = None
+        else:
+            self.tag_member = QAPISchemaObjectTypeMember('type', tag_enum,
+                                                         False)
+        self.variants = variants
+
+    def check(self, schema, members, seen):
+        if self.tag_name:
+            self.tag_member = seen[self.tag_name]
+        else:
+            self.tag_member.check(schema, members, seen)
+        assert isinstance(self.tag_member.type, QAPISchemaEnumType)
+        for v in self.variants:
+            vseen = dict(seen)
+            v.check(schema, self.tag_member.type, vseen)
+
+
+class QAPISchemaObjectTypeVariant(QAPISchemaObjectTypeMember):
+    def __init__(self, name, typ):
+        QAPISchemaObjectTypeMember.__init__(self, name, typ, False)
+
+    def check(self, schema, tag_type, seen):
+        QAPISchemaObjectTypeMember.check(self, schema, [], seen)
+        assert self.name in tag_type.values
+
+
+class QAPISchemaAlternateType(QAPISchemaType):
+    def __init__(self, name, info, variants):
+        QAPISchemaType.__init__(self, name, info)
+        assert isinstance(variants, QAPISchemaObjectTypeVariants)
+        assert not variants.tag_name
+        self.variants = variants
+
+    def check(self, schema):
+        self.variants.check(schema, [], {})
+
+
+class QAPISchemaCommand(QAPISchemaEntity):
+    def __init__(self, name, info, arg_type, ret_type, gen, success_response):
+        QAPISchemaEntity.__init__(self, name, info)
+        assert not arg_type or isinstance(arg_type, str)
+        assert not ret_type or isinstance(ret_type, str)
+        self._arg_type_name = arg_type
+        self.arg_type = None
+        self._ret_type_name = ret_type
+        self.ret_type = None
+        self.gen = gen
+        self.success_response = success_response
+
+    def check(self, schema):
+        if self._arg_type_name:
+            self.arg_type = schema.lookup_type(self._arg_type_name)
+            assert isinstance(self.arg_type, QAPISchemaObjectType)
+            assert not self.arg_type.variants   # not implemented
+        if self._ret_type_name:
+            self.ret_type = schema.lookup_type(self._ret_type_name)
+            assert isinstance(self.ret_type, QAPISchemaType)
+
+
+class QAPISchemaEvent(QAPISchemaEntity):
+    def __init__(self, name, info, arg_type):
+        QAPISchemaEntity.__init__(self, name, info)
+        assert not arg_type or isinstance(arg_type, str)
+        self._arg_type_name = arg_type
+        self.arg_type = None
+
+    def check(self, schema):
+        if self._arg_type_name:
+            self.arg_type = schema.lookup_type(self._arg_type_name)
+            assert isinstance(self.arg_type, QAPISchemaObjectType)
+            assert not self.arg_type.variants   # not implemented
+
+
+class QAPISchema(object):
+    def __init__(self, fname):
+        try:
+            self.exprs = check_exprs(QAPISchemaParser(open(fname, "r")).exprs)
+        except (QAPISchemaError, QAPIExprError), err:
+            print >>sys.stderr, err
+            exit(1)
+        self._entity_dict = {}
+        self._def_predefineds()
+        self._def_exprs()
+        self.check()
+
+    def get_exprs(self):
+        return [expr_elem['expr'] for expr_elem in self.exprs]
+
+    def _def_entity(self, ent):
+        assert ent.name not in self._entity_dict
+        self._entity_dict[ent.name] = ent
+
+    def lookup_entity(self, name, typ=None):
+        ent = self._entity_dict.get(name)
+        if typ and not isinstance(ent, typ):
+            return None
+        return ent
+
+    def lookup_type(self, name):
+        return self.lookup_entity(name, QAPISchemaType)
+
+    def _def_builtin_type(self, name):
+        self._def_entity(QAPISchemaBuiltinType(name))
+        if name != '**':
+            self._make_array_type(name)         # TODO really needed?
+
+    def _def_predefineds(self):
+        for t in ['str', 'number', 'int', 'int8', 'int16', 'int32', 'int64',
+                  'uint8', 'uint16', 'uint32', 'uint64', 'size', 'bool', '**']:
+            self._def_builtin_type(t)
+
+    def _make_implicit_enum_type(self, name, values):
+        name = name + 'Kind'
+        self._def_entity(QAPISchemaEnumType(name, None, values, None))
+        return name
+
+    def _make_array_type(self, element_type):
+        name = element_type + 'List'
+        if not self.lookup_type(name):
+            self._def_entity(QAPISchemaArrayType(name, None, element_type))
+        return name
+
+    def _make_implicit_object_type(self, name, role, members):
+        if not members:
+            return None
+        name = ':obj-%s-%s' % (name, role)
+        if not self.lookup_entity(name, QAPISchemaObjectType):
+            self._def_entity(QAPISchemaObjectType(name, None, None,
+                                                  members, None))
+        return name
+
+    def _def_enum_type(self, expr, info):
+        name = expr['enum']
+        data = expr['data']
+        prefix = expr.get('prefix')
+        self._def_entity(QAPISchemaEnumType(name, info, data, prefix))
+        self._make_array_type(name)     # TODO really needed?
+
+    def _make_member(self, name, typ):
+        optional = False
+        if name.startswith('*'):
+            name = name[1:]
+            optional = True
+        if isinstance(typ, list):
+            assert len(typ) == 1
+            typ = self._make_array_type(typ[0])
+        return QAPISchemaObjectTypeMember(name, typ, optional)
+
+    def _make_members(self, data):
+        return [self._make_member(key, value)
+                for (key, value) in data.iteritems()]
+
+    def _def_struct_type(self, expr, info):
+        name = expr['struct']
+        base = expr.get('base')
+        data = expr['data']
+        self._def_entity(QAPISchemaObjectType(name, info, base,
+                                              self._make_members(data),
+                                              None))
+        self._make_array_type(name)     # TODO really needed?
+
+    def _make_variant(self, case, typ):
+        return QAPISchemaObjectTypeVariant(case, typ)
+
+    def _make_simple_variant(self, case, typ):
+        if isinstance(typ, list):
+            assert len(typ) == 1
+            typ = self._make_array_type(typ[0])
+        typ = self._make_implicit_object_type(typ, 'wrapper',
+                                              [self._make_member('data', typ)])
+        return QAPISchemaObjectTypeVariant(case, typ)
+
+    def _make_tag_enum(self, type_name, variants):
+        return self._make_implicit_enum_type(type_name,
+                                             [v.name for v in variants])
+
+    def _def_union_type(self, expr, info):
+        name = expr['union']
+        data = expr['data']
+        base = expr.get('base')
+        tag_name = expr.get('discriminator')
+        tag_enum = None
+        if tag_name:
+            variants = [self._make_variant(key, value)
+                        for (key, value) in data.iteritems()]
+        else:
+            variants = [self._make_simple_variant(key, value)
+                        for (key, value) in data.iteritems()]
+            tag_enum = self._make_tag_enum(name, variants)
+        self._def_entity(
+            QAPISchemaObjectType(name, info, base,
+                                 self._make_members(OrderedDict()),
+                                 QAPISchemaObjectTypeVariants(tag_name,
+                                                              tag_enum,
+                                                              variants)))
+        self._make_array_type(name)     # TODO really needed?
+
+    def _def_alternate_type(self, expr, info):
+        name = expr['alternate']
+        data = expr['data']
+        variants = [self._make_variant(key, value)
+                    for (key, value) in data.iteritems()]
+        tag_enum = self._make_tag_enum(name, variants)
+        self._def_entity(
+            QAPISchemaAlternateType(name, info,
+                                    QAPISchemaObjectTypeVariants(None,
+                                                                 tag_enum,
+                                                                 variants)))
+        self._make_array_type(name)     # TODO really needed?
+
+    def _def_command(self, expr, info):
+        name = expr['command']
+        data = expr.get('data')
+        rets = expr.get('returns')
+        gen = expr.get('gen', True)
+        success_response = expr.get('success-response', True)
+        if isinstance(data, OrderedDict):
+            data = self._make_implicit_object_type(name, 'arg',
+                                                   self._make_members(data))
+        if isinstance(rets, list):
+            assert len(rets) == 1
+            rets = self._make_array_type(rets[0])
+        self._def_entity(QAPISchemaCommand(name, info, data, rets, gen,
+                                           success_response))
+
+    def _def_event(self, expr, info):
+        name = expr['event']
+        data = expr.get('data')
+        if isinstance(data, OrderedDict):
+            data = self._make_implicit_object_type(name, 'arg',
+                                                   self._make_members(data))
+        self._def_entity(QAPISchemaEvent(name, info, data))
+
+    def _def_exprs(self):
+        for expr_elem in self.exprs:
+            expr = expr_elem['expr']
+            info = expr_elem['info']
+            if 'enum' in expr:
+                self._def_enum_type(expr, info)
+            elif 'struct' in expr:
+                self._def_struct_type(expr, info)
+            elif 'union' in expr:
+                self._def_union_type(expr, info)
+            elif 'alternate' in expr:
+                self._def_alternate_type(expr, info)
+            elif 'command' in expr:
+                self._def_command(expr, info)
+            elif 'event' in expr:
+                self._def_event(expr, info)
+            else:
+                assert False
+
+    def check(self):
+        for ent in self._entity_dict.values():
+            ent.check(self)
 
-def parse_schema(fname):
-    try:
-        schema = QAPISchemaParser(open(fname, "r"))
-        return check_exprs(schema.exprs)
-    except (QAPISchemaError, QAPIExprError), e:
-        print >>sys.stderr, e
-        exit(1)
 
 #
 # Code generation helpers

tests/qapi-schema/test-qapi.py

@@ -16,7 +16,7 @@ import os
 import sys
 
 try:
-    exprs = parse_schema(sys.argv[1])
+    exprs = QAPISchema(sys.argv[1]).get_exprs()
 except SystemExit:
     raise