path: root/scripts/qapi/schema.py

# -*- coding: utf-8 -*-
#
# QAPI schema internal representation
#
# Copyright (c) 2015-2019 Red Hat Inc.
#
# Authors:
#  Markus Armbruster <armbru@redhat.com>
#  Eric Blake <eblake@redhat.com>
#  Marc-André Lureau <marcandre.lureau@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2.
# See the COPYING file in the top-level directory.

# pylint: disable=too-many-lines

# TODO catching name collisions in generated code would be nice

from abc import ABC, abstractmethod
from collections import OrderedDict
import os
import re
from typing import List, Optional, cast

from .common import (
    POINTER_SUFFIX,
    c_name,
    cgen_ifcond,
    docgen_ifcond,
    gen_endif,
    gen_if,
)
from .error import QAPIError, QAPISemError, QAPISourceError
from .expr import check_exprs
from .parser import QAPIExpression, QAPISchemaParser


class QAPISchemaIfCond:
    def __init__(self, ifcond=None):
        self.ifcond = ifcond

    def _cgen(self):
        return cgen_ifcond(self.ifcond)

    def gen_if(self):
        return gen_if(self._cgen())

    def gen_endif(self):
        return gen_endif(self._cgen())

    def docgen(self):
        return docgen_ifcond(self.ifcond)

    def is_present(self):
        return bool(self.ifcond)


class QAPISchemaEntity:
    """
    A schema entity.

    This is either a directive, such as include, or a definition.
    The latter uses sub-class `QAPISchemaDefinition`.
    """
    def __init__(self, info):
        self._module = None
        # For explicitly defined entities, info points to the (explicit)
        # definition.  For builtins (and their arrays), info is None.
        # For implicitly defined entities, info points to a place that
        # triggered the implicit definition (there may be more than one
        # such place).
        self.info = info
        self._checked = False

    def __repr__(self):
        return "<%s at 0x%x>" % (type(self).__name__, id(self))

    def check(self, schema):
        # pylint: disable=unused-argument
        self._checked = True

    def connect_doc(self, doc=None):
        pass

    def _set_module(self, schema, info):
        assert self._checked
        fname = info.fname if info else QAPISchemaModule.BUILTIN_MODULE_NAME
        self._module = schema.module_by_fname(fname)
        self._module.add_entity(self)

    def set_module(self, schema):
        self._set_module(schema, self.info)

    def visit(self, visitor):
        # pylint: disable=unused-argument
        assert self._checked


class QAPISchemaDefinition(QAPISchemaEntity):
    meta: Optional[str] = None

    def __init__(self, name: str, info, doc, ifcond=None, features=None):
        assert isinstance(name, str)
        super().__init__(info)
        for f in features or []:
            assert isinstance(f, QAPISchemaFeature)
            f.set_defined_in(name)
        self.name = name
        self.doc = doc
        self._ifcond = ifcond or QAPISchemaIfCond()
        self.features = features or []

    def __repr__(self):
        return "<%s:%s at 0x%x>" % (type(self).__name__, self.name,
                                    id(self))

    def c_name(self):
        return c_name(self.name)

    def check(self, schema):
        assert not self._checked
        super().check(schema)
        seen = {}
        for f in self.features:
            f.check_clash(self.info, seen)

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        if doc:
            for f in self.features:
                doc.connect_feature(f)

    @property
    def ifcond(self):
        assert self._checked
        return self._ifcond

    def is_implicit(self):
        return not self.info

    def describe(self):
        assert self.meta
        return "%s '%s'" % (self.meta, self.name)


class QAPISchemaVisitor:
    def visit_begin(self, schema):
        pass

    def visit_end(self):
        pass

    def visit_module(self, name):
        pass

    def visit_needed(self, entity):
        # pylint: disable=unused-argument
        # Default to visiting everything
        return True

    def visit_include(self, name, info):
        pass

    def visit_builtin_type(self, name, info, json_type):
        pass

    def visit_enum_type(self, name, info, ifcond, features, members, prefix):
        pass

    def visit_array_type(self, name, info, ifcond, element_type):
        pass

    def visit_object_type(self, name, info, ifcond, features,
                          base, members, variants):
        pass

    def visit_object_type_flat(self, name, info, ifcond, features,
                               members, variants):
        pass

    def visit_alternate_type(self, name, info, ifcond, features, variants):
        pass

    def visit_command(self, name, info, ifcond, features,
                      arg_type, ret_type, gen, success_response, boxed,
                      allow_oob, allow_preconfig, coroutine):
        pass

    def visit_event(self, name, info, ifcond, features, arg_type, boxed):
        pass


class QAPISchemaModule:

    BUILTIN_MODULE_NAME = './builtin'

    def __init__(self, name):
        self.name = name
        self._entity_list = []

    @staticmethod
    def is_system_module(name: str) -> bool:
        """
        System modules are internally defined modules.

        Their names start with the "./" prefix.
        """
        return name.startswith('./')

    @classmethod
    def is_user_module(cls, name: str) -> bool:
        """
        User modules are those defined by the user in qapi JSON files.

        They do not start with the "./" prefix.
        """
        return not cls.is_system_module(name)

    @classmethod
    def is_builtin_module(cls, name: str) -> bool:
        """
        The built-in module is a single System module for the built-in types.

        It is always "./builtin".
        """
        return name == cls.BUILTIN_MODULE_NAME

    def add_entity(self, ent):
        self._entity_list.append(ent)

    def visit(self, visitor):
        visitor.visit_module(self.name)
        for entity in self._entity_list:
            if visitor.visit_needed(entity):
                entity.visit(visitor)


class QAPISchemaInclude(QAPISchemaEntity):
    def __init__(self, sub_module, info):
        super().__init__(info)
        self._sub_module = sub_module

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_include(self._sub_module.name, self.info)


class QAPISchemaType(QAPISchemaDefinition, ABC):
    # Return the C type for common use.
    # For the types we commonly box, this is a pointer type.
    @abstractmethod
    def c_type(self):
        pass

    # Return the C type to be used in a parameter list.
    def c_param_type(self):
        return self.c_type()

    # Return the C type to be used where we suppress boxing.
    def c_unboxed_type(self):
        return self.c_type()

    @abstractmethod
    def json_type(self):
        pass

    def alternate_qtype(self):
        json2qtype = {
            'null':    'QTYPE_QNULL',
            'string':  'QTYPE_QSTRING',
            'number':  'QTYPE_QNUM',
            'int':     'QTYPE_QNUM',
            'boolean': 'QTYPE_QBOOL',
            'array':   'QTYPE_QLIST',
            'object':  'QTYPE_QDICT'
        }
        return json2qtype.get(self.json_type())

    def doc_type(self):
        if self.is_implicit():
            return None
        return self.name

    def need_has_if_optional(self):
        # When FOO is a pointer, has_FOO == !!FOO, i.e. has_FOO is redundant.
        # Except for arrays; see QAPISchemaArrayType.need_has_if_optional().
        return not self.c_type().endswith(POINTER_SUFFIX)

    def check(self, schema):
        super().check(schema)
        for feat in self.features:
            if feat.is_special():
                raise QAPISemError(
                    self.info,
                    f"feature '{feat.name}' is not supported for types")

    def describe(self):
        assert self.meta
        return "%s type '%s'" % (self.meta, self.name)


class QAPISchemaBuiltinType(QAPISchemaType):
    meta = 'built-in'

    def __init__(self, name, json_type, c_type):
        super().__init__(name, None, None)
        assert not c_type or isinstance(c_type, str)
        assert json_type in ('string', 'number', 'int', 'boolean', 'null',
                             'value')
        self._json_type_name = json_type
        self._c_type_name = c_type

    def c_name(self):
        return self.name

    def c_type(self):
        return self._c_type_name

    def c_param_type(self):
        if self.name == 'str':
            return 'const ' + self._c_type_name
        return self._c_type_name

    def json_type(self):
        return self._json_type_name

    def doc_type(self):
        return self.json_type()

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_builtin_type(self.name, self.info, self.json_type())


class QAPISchemaEnumType(QAPISchemaType):
    meta = 'enum'

    def __init__(self, name, info, doc, ifcond, features, members, prefix):
        super().__init__(name, info, doc, ifcond, features)
        for m in members:
            assert isinstance(m, QAPISchemaEnumMember)
            m.set_defined_in(name)
        assert prefix is None or isinstance(prefix, str)
        self.members = members
        self.prefix = prefix

    def check(self, schema):
        super().check(schema)
        seen = {}
        for m in self.members:
            m.check_clash(self.info, seen)

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        for m in self.members:
            m.connect_doc(doc)

    def is_implicit(self):
        # See QAPISchema._def_predefineds()
        return self.name == 'QType'

    def c_type(self):
        return c_name(self.name)

    def member_names(self):
        return [m.name for m in self.members]

    def json_type(self):
        return 'string'

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_enum_type(
            self.name, self.info, self.ifcond, self.features,
            self.members, self.prefix)


class QAPISchemaArrayType(QAPISchemaType):
    meta = 'array'

    def __init__(self, name, info, element_type):
        super().__init__(name, info, None)
        assert isinstance(element_type, str)
        self._element_type_name = element_type
        self.element_type: QAPISchemaType

    def need_has_if_optional(self):
        # When FOO is an array, we still need has_FOO to distinguish
        # absent (!has_FOO) from present and empty (has_FOO && !FOO).
        return True

    def check(self, schema):
        super().check(schema)
        self.element_type = schema.resolve_type(
            self._element_type_name, self.info,
            self.info.defn_meta if self.info else None)
        assert not isinstance(self.element_type, QAPISchemaArrayType)

    def set_module(self, schema):
        self._set_module(schema, self.element_type.info)

    @property
    def ifcond(self):
        assert self._checked
        return self.element_type.ifcond

    def is_implicit(self):
        return True

    def c_type(self):
        return c_name(self.name) + POINTER_SUFFIX

    def json_type(self):
        return 'array'

    def doc_type(self):
        elt_doc_type = self.element_type.doc_type()
        if not elt_doc_type:
            return None
        return 'array of ' + elt_doc_type

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_array_type(self.name, self.info, self.ifcond,
                                 self.element_type)

    def describe(self):
        assert self.meta
        return "%s type ['%s']" % (self.meta, self._element_type_name)


class QAPISchemaObjectType(QAPISchemaType):
    def __init__(self, name, info, doc, ifcond, features,
                 base, local_members, variants):
        # struct has local_members, optional base, and no variants
        # union has base, variants, and no local_members
        super().__init__(name, info, doc, ifcond, features)
        self.meta = 'union' if variants else 'struct'
        assert base is None or isinstance(base, str)
        for m in local_members:
            assert isinstance(m, QAPISchemaObjectTypeMember)
            m.set_defined_in(name)
        if variants is not None:
            assert isinstance(variants, QAPISchemaVariants)
            variants.set_defined_in(name)
        self._base_name = base
        self.base = None
        self.local_members = local_members
        self.variants = variants
        self.members: List[QAPISchemaObjectTypeMember]
        self._check_complete = False

    def check(self, schema):
        # This calls another type T's .check() exactly when the C
        # struct emitted by gen_object() contains that T's C struct
        # (pointers don't count).
        if self._check_complete:
            # A previous .check() completed: nothing to do
            return
        if self._checked:
            # Recursed: C struct contains itself
            raise QAPISemError(self.info,
                               "object %s contains itself" % self.name)

        super().check(schema)
        assert self._checked and not self._check_complete

        seen = OrderedDict()
        if self._base_name:
            self.base = schema.resolve_type(self._base_name, self.info,
                                            "'base'")
            if (not isinstance(self.base, QAPISchemaObjectType)
                    or self.base.variants):
                raise QAPISemError(
                    self.info,
                    "'base' requires a struct type, %s isn't"
                    % self.base.describe())
            self.base.check(schema)
            self.base.check_clash(self.info, seen)
        for m in self.local_members:
            m.check(schema)
            m.check_clash(self.info, seen)

        # self.check_clash() works in terms of the supertype, but
        # self.members is declared List[QAPISchemaObjectTypeMember].
        # Cast down to the subtype.
        members = cast(List[QAPISchemaObjectTypeMember], list(seen.values()))

        if self.variants:
            self.variants.check(schema, seen)
            self.variants.check_clash(self.info, seen)

        self.members = members
        self._check_complete = True  # mark completed

    # Check that the members of this type do not cause duplicate JSON members,
    # and update seen to track the members seen so far. Report any errors
    # on behalf of info, which is not necessarily self.info
    def check_clash(self, info, seen):
        assert self._checked
        for m in self.members:
            m.check_clash(info, seen)
        if self.variants:
            self.variants.check_clash(info, seen)

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        if self.base and self.base.is_implicit():
            self.base.connect_doc(doc)
        for m in self.local_members:
            m.connect_doc(doc)

    def is_implicit(self):
        # See QAPISchema._make_implicit_object_type(), as well as
        # _def_predefineds()
        return self.name.startswith('q_')

    def is_empty(self):
        return not self.members and not self.variants

    def has_conditional_members(self):
        return any(m.ifcond.is_present() for m in self.members)

    def c_name(self):
        assert self.name != 'q_empty'
        return super().c_name()

    def c_type(self):
        assert not self.is_implicit()
        return c_name(self.name) + POINTER_SUFFIX

    def c_unboxed_type(self):
        return c_name(self.name)

    def json_type(self):
        return 'object'

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_object_type(
            self.name, self.info, self.ifcond, self.features,
            self.base, self.local_members, self.variants)
        visitor.visit_object_type_flat(
            self.name, self.info, self.ifcond, self.features,
            self.members, self.variants)


class QAPISchemaAlternateType(QAPISchemaType):
    meta = 'alternate'

    def __init__(self, name, info, doc, ifcond, features, variants):
        super().__init__(name, info, doc, ifcond, features)
        assert isinstance(variants, QAPISchemaVariants)
        assert variants.tag_member
        variants.set_defined_in(name)
        variants.tag_member.set_defined_in(self.name)
        self.variants = variants

    def check(self, schema):
        super().check(schema)
        self.variants.tag_member.check(schema)
        # Not calling self.variants.check_clash(), because there's nothing
        # to clash with
        self.variants.check(schema, {})
        # Alternate branch names have no relation to the tag enum values;
        # so we have to check for potential name collisions ourselves.
        seen = {}
        types_seen = {}
        for v in self.variants.variants:
            v.check_clash(self.info, seen)
            qtype = v.type.alternate_qtype()
            if not qtype:
                raise QAPISemError(
                    self.info,
                    "%s cannot use %s"
                    % (v.describe(self.info), v.type.describe()))
            conflicting = set([qtype])
            if qtype == 'QTYPE_QSTRING':
                if isinstance(v.type, QAPISchemaEnumType):
                    for m in v.type.members:
                        if m.name in ['on', 'off']:
                            conflicting.add('QTYPE_QBOOL')
                        if re.match(r'[-+0-9.]', m.name):
                            # lazy, could be tightened
                            conflicting.add('QTYPE_QNUM')
                else:
                    conflicting.add('QTYPE_QNUM')
                    conflicting.add('QTYPE_QBOOL')
            for qt in conflicting:
                if qt in types_seen:
                    raise QAPISemError(
                        self.info,
                        "%s can't be distinguished from '%s'"
                        % (v.describe(self.info), types_seen[qt]))
                types_seen[qt] = v.name

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        for v in self.variants.variants:
            v.connect_doc(doc)

    def c_type(self):
        return c_name(self.name) + POINTER_SUFFIX

    def json_type(self):
        return 'value'

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_alternate_type(
            self.name, self.info, self.ifcond, self.features, self.variants)


class QAPISchemaVariants:
    def __init__(self, tag_name, info, tag_member, variants):
        # Unions pass tag_name but not tag_member.
        # Alternates pass tag_member but not tag_name.
        # After check(), tag_member is always set.
        assert bool(tag_member) != bool(tag_name)
        assert (isinstance(tag_name, str) or
                isinstance(tag_member, QAPISchemaObjectTypeMember))
        for v in variants:
            assert isinstance(v, QAPISchemaVariant)
        self._tag_name = tag_name
        self.info = info
        self._tag_member: Optional[QAPISchemaObjectTypeMember] = tag_member
        self.variants = variants

    @property
    def tag_member(self) -> 'QAPISchemaObjectTypeMember':
        if self._tag_member is None:
            raise RuntimeError(
                "QAPISchemaVariants has no tag_member property until "
                "after check() has been run."
            )
        return self._tag_member

    def set_defined_in(self, name):
        for v in self.variants:
            v.set_defined_in(name)

    def check(self, schema, seen):
        if self._tag_name:      # union
            # We need to narrow the member type:
            tmp = seen.get(c_name(self._tag_name))
            assert tmp is None or isinstance(tmp, QAPISchemaObjectTypeMember)
            self._tag_member = tmp

            base = "'base'"
            # Pointing to the base type when not implicit would be
            # nice, but we don't know it here
            if not self._tag_member or self._tag_name != self._tag_member.name:
                raise QAPISemError(
                    self.info,
                    "discriminator '%s' is not a member of %s"
                    % (self._tag_name, base))
            # Here we do:
            assert self.tag_member.defined_in
            base_type = schema.lookup_type(self.tag_member.defined_in)
            assert base_type
            if not base_type.is_implicit():
                base = "base type '%s'" % self.tag_member.defined_in
            if not isinstance(self.tag_member.type, QAPISchemaEnumType):
                raise QAPISemError(
                    self.info,
                    "discriminator member '%s' of %s must be of enum type"
                    % (self._tag_name, base))
            if self.tag_member.optional:
                raise QAPISemError(
                    self.info,
                    "discriminator member '%s' of %s must not be optional"
                    % (self._tag_name, base))
            if self.tag_member.ifcond.is_present():
                raise QAPISemError(
                    self.info,
                    "discriminator member '%s' of %s must not be conditional"
                    % (self._tag_name, base))
        else:                   # alternate
            assert self._tag_member
            assert isinstance(self.tag_member.type, QAPISchemaEnumType)
            assert not self.tag_member.optional
            assert not self.tag_member.ifcond.is_present()
        if self._tag_name:      # union
            # branches that are not explicitly covered get an empty type
            assert self.tag_member.defined_in
            cases = {v.name for v in self.variants}
            for m in self.tag_member.type.members:
                if m.name not in cases:
                    v = QAPISchemaVariant(m.name, self.info,
                                          'q_empty', m.ifcond)
                    v.set_defined_in(self.tag_member.defined_in)
                    self.variants.append(v)
        if not self.variants:
            raise QAPISemError(self.info, "union has no branches")
        for v in self.variants:
            v.check(schema)
            # Union names must match enum values; alternate names are
            # checked separately. Use 'seen' to tell the two apart.
            if seen:
                if v.name not in self.tag_member.type.member_names():
                    raise QAPISemError(
                        self.info,
                        "branch '%s' is not a value of %s"
                        % (v.name, self.tag_member.type.describe()))
                if not isinstance(v.type, QAPISchemaObjectType):
                    raise QAPISemError(
                        self.info,
                        "%s cannot use %s"
                        % (v.describe(self.info), v.type.describe()))
                v.type.check(schema)

    def check_clash(self, info, seen):
        for v in self.variants:
            # Reset seen map for each variant, since qapi names from one
            # branch do not affect another branch.
            #
            # v.type's typing is enforced in check() above.
            assert isinstance(v.type, QAPISchemaObjectType)
            v.type.check_clash(info, dict(seen))


class QAPISchemaMember:
    """ Represents object members, enum members and features """
    role = 'member'

    def __init__(self, name, info, ifcond=None):
        assert isinstance(name, str)
        self.name = name
        self.info = info
        self.ifcond = ifcond or QAPISchemaIfCond()
        self.defined_in = None

    def set_defined_in(self, name):
        assert not self.defined_in
        self.defined_in = name

    def check_clash(self, info, seen):
        cname = c_name(self.name)
        if cname in seen:
            raise QAPISemError(
                info,
                "%s collides with %s"
                % (self.describe(info), seen[cname].describe(info)))
        seen[cname] = self

    def connect_doc(self, doc):
        if doc:
            doc.connect_member(self)

    def describe(self, info):
        role = self.role
        meta = 'type'
        defined_in = self.defined_in
        assert defined_in

        if defined_in.startswith('q_obj_'):
            # See QAPISchema._make_implicit_object_type() - reverse the
            # mapping there to create a nice human-readable description
            defined_in = defined_in[6:]
            if defined_in.endswith('-arg'):
                # Implicit type created for a command's dict 'data'
                assert role == 'member'
                role = 'parameter'
                meta = 'command'
                defined_in = defined_in[:-4]
            elif defined_in.endswith('-base'):
                # Implicit type created for a union's dict 'base'
                role = 'base ' + role
                defined_in = defined_in[:-5]
            else:
                assert False

        assert info is not None
        if defined_in != info.defn_name:
            return "%s '%s' of %s '%s'" % (role, self.name, meta, defined_in)
        return "%s '%s'" % (role, self.name)


class QAPISchemaEnumMember(QAPISchemaMember):
    role = 'value'

    def __init__(self, name, info, ifcond=None, features=None):
        super().__init__(name, info, ifcond)
        for f in features or []:
            assert isinstance(f, QAPISchemaFeature)
            f.set_defined_in(name)
        self.features = features or []

    def connect_doc(self, doc):
        super().connect_doc(doc)
        if doc:
            for f in self.features:
                doc.connect_feature(f)


class QAPISchemaFeature(QAPISchemaMember):
    role = 'feature'

    def is_special(self):
        return self.name in ('deprecated', 'unstable')


class QAPISchemaObjectTypeMember(QAPISchemaMember):
    def __init__(self, name, info, typ, optional, ifcond=None, features=None):
        super().__init__(name, info, ifcond)
        assert isinstance(typ, str)
        assert isinstance(optional, bool)
        for f in features or []:
            assert isinstance(f, QAPISchemaFeature)
            f.set_defined_in(name)
        self._type_name = typ
        self.type: QAPISchemaType  # set during check()
        self.optional = optional
        self.features = features or []

    def need_has(self):
        assert self.type
        return self.optional and self.type.need_has_if_optional()

    def check(self, schema):
        assert self.defined_in
        self.type = schema.resolve_type(self._type_name, self.info,
                                        self.describe)
        seen = {}
        for f in self.features:
            f.check_clash(self.info, seen)

    def connect_doc(self, doc):
        super().connect_doc(doc)
        if doc:
            for f in self.features:
                doc.connect_feature(f)


class QAPISchemaVariant(QAPISchemaObjectTypeMember):
    role = 'branch'

    def __init__(self, name, info, typ, ifcond=None):
        super().__init__(name, info, typ, False, ifcond)


class QAPISchemaCommand(QAPISchemaDefinition):
    meta = 'command'

    def __init__(self, name, info, doc, ifcond, features,
                 arg_type, ret_type,
                 gen, success_response, boxed, allow_oob, allow_preconfig,
                 coroutine):
        super().__init__(name, info, doc, ifcond, features)
        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
        self.boxed = boxed
        self.allow_oob = allow_oob
        self.allow_preconfig = allow_preconfig
        self.coroutine = coroutine

    def check(self, schema):
        assert self.info is not None
        super().check(schema)
        if self._arg_type_name:
            arg_type = schema.resolve_type(
                self._arg_type_name, self.info, "command's 'data'")
            if not isinstance(arg_type, QAPISchemaObjectType):
                raise QAPISemError(
                    self.info,
                    "command's 'data' cannot take %s"
                    % arg_type.describe())
            self.arg_type = arg_type
            if self.arg_type.variants and not self.boxed:
                raise QAPISemError(
                    self.info,
                    "command's 'data' can take %s only with 'boxed': true"
                    % self.arg_type.describe())
            self.arg_type.check(schema)
            if self.arg_type.has_conditional_members() and not self.boxed:
                raise QAPISemError(
                    self.info,
                    "conditional command arguments require 'boxed': true")
        if self._ret_type_name:
            self.ret_type = schema.resolve_type(
                self._ret_type_name, self.info, "command's 'returns'")
            if self.name not in self.info.pragma.command_returns_exceptions:
                typ = self.ret_type
                if isinstance(typ, QAPISchemaArrayType):
                    assert typ
                    typ = typ.element_type
                if not isinstance(typ, QAPISchemaObjectType):
                    raise QAPISemError(
                        self.info,
                        "command's 'returns' cannot take %s"
                        % self.ret_type.describe())

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        if doc:
            if self.arg_type and self.arg_type.is_implicit():
                self.arg_type.connect_doc(doc)

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_command(
            self.name, self.info, self.ifcond, self.features,
            self.arg_type, self.ret_type, self.gen, self.success_response,
            self.boxed, self.allow_oob, self.allow_preconfig,
            self.coroutine)


class QAPISchemaEvent(QAPISchemaDefinition):
    meta = 'event'

    def __init__(self, name, info, doc, ifcond, features, arg_type, boxed):
        super().__init__(name, info, doc, ifcond, features)
        assert not arg_type or isinstance(arg_type, str)
        self._arg_type_name = arg_type
        self.arg_type = None
        self.boxed = boxed

    def check(self, schema):
        super().check(schema)
        if self._arg_type_name:
            typ = schema.resolve_type(
                self._arg_type_name, self.info, "event's 'data'")
            if not isinstance(typ, QAPISchemaObjectType):
                raise QAPISemError(
                    self.info,
                    "event's 'data' cannot take %s"
                    % typ.describe())
            self.arg_type = typ
            if self.arg_type.variants and not self.boxed:
                raise QAPISemError(
                    self.info,
                    "event's 'data' can take %s only with 'boxed': true"
                    % self.arg_type.describe())
            self.arg_type.check(schema)
            if self.arg_type.has_conditional_members() and not self.boxed:
                raise QAPISemError(
                    self.info,
                    "conditional event arguments require 'boxed': true")

    def connect_doc(self, doc=None):
        super().connect_doc(doc)
        doc = doc or self.doc
        if doc:
            if self.arg_type and self.arg_type.is_implicit():
                self.arg_type.connect_doc(doc)

    def visit(self, visitor):
        super().visit(visitor)
        visitor.visit_event(
            self.name, self.info, self.ifcond, self.features,
            self.arg_type, self.boxed)


class QAPISchema:
    def __init__(self, fname):
        self.fname = fname

        try:
            parser = QAPISchemaParser(fname)
        except OSError as err:
            raise QAPIError(
                f"can't read schema file '{fname}': {err.strerror}"
            ) from err

        exprs = check_exprs(parser.exprs)
        self.docs = parser.docs
        self._entity_list = []
        self._entity_dict = {}
        self._module_dict = OrderedDict()
        self._schema_dir = os.path.dirname(fname)
        self._make_module(QAPISchemaModule.BUILTIN_MODULE_NAME)
        self._make_module(fname)
        self._predefining = True
        self._def_predefineds()
        self._predefining = False
        self._def_exprs(exprs)
        self.check()

    def _def_entity(self, ent):
        self._entity_list.append(ent)

    def _def_definition(self, defn):
        # Only the predefined types are allowed to not have info
        assert defn.info or self._predefining
        self._def_entity(defn)
        # TODO reject names that differ only in '_' vs. '.'  vs. '-',
        # because they're liable to clash in generated C.
        other_defn = self._entity_dict.get(defn.name)
        if other_defn:
            if other_defn.info:
                where = QAPISourceError(other_defn.info, "previous definition")
                raise QAPISemError(
                    defn.info,
                    "'%s' is already defined\n%s" % (defn.name, where))
            raise QAPISemError(
                defn.info, "%s is already defined" % other_defn.describe())
        self._entity_dict[defn.name] = defn

    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):
        typ = self.lookup_entity(name, QAPISchemaType)
        assert typ is None or isinstance(typ, QAPISchemaType)
        return typ

    def resolve_type(self, name, info, what):
        typ = self.lookup_type(name)
        if not typ:
            assert info and what  # built-in types must not fail lookup
            if callable(what):
                what = what(info)
            raise QAPISemError(
                info, "%s uses unknown type '%s'" % (what, name))
        return typ

    def _module_name(self, fname: str) -> str:
        if QAPISchemaModule.is_system_module(fname):
            return fname
        return os.path.relpath(fname, self._schema_dir)

    def _make_module(self, fname):
        name = self._module_name(fname)
        if name not in self._module_dict:
            self._module_dict[name] = QAPISchemaModule(name)
        return self._module_dict[name]

    def module_by_fname(self, fname):
        name = self._module_name(fname)
        return self._module_dict[name]

    def _def_include(self, expr: QAPIExpression):
        include = expr['include']
        assert expr.doc is None
        self._def_entity(
            QAPISchemaInclude(self._make_module(include), expr.info))

    def _def_builtin_type(self, name, json_type, c_type):
        self._def_definition(QAPISchemaBuiltinType(name, json_type, c_type))
        # Instantiating only the arrays that are actually used would
        # be nice, but we can't as long as their generated code
        # (qapi-builtin-types.[ch]) may be shared by some other
        # schema.
        self._make_array_type(name, None)

    def _def_predefineds(self):
        for t in [('str',    'string',  'char' + POINTER_SUFFIX),
                  ('number', 'number',  'double'),
                  ('int',    'int',     'int64_t'),
                  ('int8',   'int',     'int8_t'),
                  ('int16',  'int',     'int16_t'),
                  ('int32',  'int',     'int32_t'),
                  ('int64',  'int',     'int64_t'),
                  ('uint8',  'int',     'uint8_t'),
                  ('uint16', 'int',     'uint16_t'),
                  ('uint32', 'int',     'uint32_t'),
                  ('uint64', 'int',     'uint64_t'),
                  ('size',   'int',     'uint64_t'),
                  ('bool',   'boolean', 'bool'),
                  ('any',    'value',   'QObject' + POINTER_SUFFIX),
                  ('null',   'null',    'QNull' + POINTER_SUFFIX)]:
            self._def_builtin_type(*t)
        self.the_empty_object_type = QAPISchemaObjectType(
            'q_empty', None, None, None, None, None, [], None)
        self._def_definition(self.the_empty_object_type)

        qtypes = ['none', 'qnull', 'qnum', 'qstring', 'qdict', 'qlist',
                  'qbool']
        qtype_values = self._make_enum_members(
            [{'name': n} for n in qtypes], None)

        self._def_definition(QAPISchemaEnumType(
            'QType', None, None, None, None, qtype_values, 'QTYPE'))

    def _make_features(self, features, info):
        if features is None:
            return []
        return [QAPISchemaFeature(f['name'], info,
                                  QAPISchemaIfCond(f.get('if')))
                for f in features]

    def _make_enum_member(self, name, ifcond, features, info):
        return QAPISchemaEnumMember(name, info,
                                    QAPISchemaIfCond(ifcond),
                                    self._make_features(features, info))

    def _make_enum_members(self, values, info):
        return [self._make_enum_member(v['name'], v.get('if'),
                                       v.get('features'), info)
                for v in values]

    def _make_array_type(self, element_type, info):
        name = element_type + 'List'    # reserved by check_defn_name_str()
        if not self.lookup_type(name):
            self._def_definition(QAPISchemaArrayType(
                name, info, element_type))
        return name

    def _make_implicit_object_type(self, name, info, ifcond, role, members):
        if not members:
            return None
        # See also QAPISchemaObjectTypeMember.describe()
        name = 'q_obj_%s-%s' % (name, role)
        typ = self.lookup_entity(name, QAPISchemaObjectType)
        if typ:
            # The implicit object type has multiple users.  This can
            # only be a duplicate definition, which will be flagged
            # later.
            pass
        else:
            self._def_definition(QAPISchemaObjectType(
                name, info, None, ifcond, None, None, members, None))
        return name

    def _def_enum_type(self, expr: QAPIExpression):
        name = expr['enum']
        data = expr['data']
        prefix = expr.get('prefix')
        ifcond = QAPISchemaIfCond(expr.get('if'))
        info = expr.info
        features = self._make_features(expr.get('features'), info)
        self._def_definition(QAPISchemaEnumType(
            name, info, expr.doc, ifcond, features,
            self._make_enum_members(data, info), prefix))

    def _make_member(self, name, typ, ifcond, features, info):
        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], info)
        return QAPISchemaObjectTypeMember(name, info, typ, optional, ifcond,
                                          self._make_features(features, info))

    def _make_members(self, data, info):
        return [self._make_member(key, value['type'],
                                  QAPISchemaIfCond(value.get('if')),
                                  value.get('features'), info)
                for (key, value) in data.items()]

    def _def_struct_type(self, expr: QAPIExpression):
        name = expr['struct']
        base = expr.get('base')
        data = expr['data']
        info = expr.info
        ifcond = QAPISchemaIfCond(expr.get('if'))
        features = self._make_features(expr.get('features'), info)
        self._def_definition(QAPISchemaObjectType(
            name, info, expr.doc, ifcond, features, base,
            self._make_members(data, info),
            None))

    def _make_variant(self, case, typ, ifcond, info):
        if isinstance(typ, list):
            assert len(typ) == 1
            typ = self._make_array_type(typ[0], info)
        return QAPISchemaVariant(case, info, typ, ifcond)

    def _def_union_type(self, expr: QAPIExpression):
        name = expr['union']
        base = expr['base']
        tag_name = expr['discriminator']
        data = expr['data']
        assert isinstance(data, dict)
        info = expr.info
        ifcond = QAPISchemaIfCond(expr.get('if'))
        features = self._make_features(expr.get('features'), info)
        if isinstance(base, dict):
            base = self._make_implicit_object_type(
                name, info, ifcond,
                'base', self._make_members(base, info))
        variants = [
            self._make_variant(key, value['type'],
                               QAPISchemaIfCond(value.get('if')),
                               info)
            for (key, value) in data.items()]
        members: List[QAPISchemaObjectTypeMember] = []
        self._def_definition(
            QAPISchemaObjectType(name, info, expr.doc, ifcond, features,
                                 base, members,
                                 QAPISchemaVariants(
                                     tag_name, info, None, variants)))

    def _def_alternate_type(self, expr: QAPIExpression):
        name = expr['alternate']
        data = expr['data']
        assert isinstance(data, dict)
        ifcond = QAPISchemaIfCond(expr.get('if'))
        info = expr.info
        features = self._make_features(expr.get('features'), info)
        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_definition(
            QAPISchemaAlternateType(
                name, info, expr.doc, ifcond, features,
                QAPISchemaVariants(None, info, tag_member, variants)))

    def _def_command(self, expr: QAPIExpression):
        name = expr['command']
        data = expr.get('data')
        rets = expr.get('returns')
        gen = expr.get('gen', True)
        success_response = expr.get('success-response', True)
        boxed = expr.get('boxed', False)
        allow_oob = expr.get('allow-oob', False)
        allow_preconfig = expr.get('allow-preconfig', False)
        coroutine = expr.get('coroutine', False)
        ifcond = QAPISchemaIfCond(expr.get('if'))
        info = expr.info
        features = self._make_features(expr.get('features'), info)
        if isinstance(data, OrderedDict):
            data = self._make_implicit_object_type(
                name, info, ifcond,
                'arg', self._make_members(data, info))
        if isinstance(rets, list):
            assert len(rets) == 1
            rets = self._make_array_type(rets[0], info)
        self._def_definition(
            QAPISchemaCommand(name, info, expr.doc, ifcond, features, data,
                              rets, gen, success_response, boxed, allow_oob,
                              allow_preconfig, coroutine))

    def _def_event(self, expr: QAPIExpression):
        name = expr['event']
        data = expr.get('data')
        boxed = expr.get('boxed', False)
        ifcond = QAPISchemaIfCond(expr.get('if'))
        info = expr.info
        features = self._make_features(expr.get('features'), info)
        if isinstance(data, OrderedDict):
            data = self._make_implicit_object_type(
                name, info, ifcond,
                'arg', self._make_members(data, info))
        self._def_definition(QAPISchemaEvent(name, info, expr.doc, ifcond,
                                             features, data, boxed))

    def _def_exprs(self, exprs):
        for expr in exprs:
            if 'enum' in expr:
                self._def_enum_type(expr)
            elif 'struct' in expr:
                self._def_struct_type(expr)
            elif 'union' in expr:
                self._def_union_type(expr)
            elif 'alternate' in expr:
                self._def_alternate_type(expr)
            elif 'command' in expr:
                self._def_command(expr)
            elif 'event' in expr:
                self._def_event(expr)
            elif 'include' in expr:
                self._def_include(expr)
            else:
                assert False

    def check(self):
        for ent in self._entity_list:
            ent.check(self)
            ent.connect_doc()
        for ent in self._entity_list:
            ent.set_module(self)
        for doc in self.docs:
            doc.check()

    def visit(self, visitor):
        visitor.visit_begin(self)
        for mod in self._module_dict.values():
            mod.visit(visitor)
        visitor.visit_end()