Re: [PATCH v2 5/7] qapi/parser: [RFC] add QAPIExpression

[John Snow]

On Wed, Feb 8, 2023 at 11:28 AM Markus Armbruster <armbru@redhat.com> wrote:
>
> John Snow <jsnow@redhat.com> writes:
>
> > The idea here is to combine 'TopLevelExpr' and 'ParsedExpression' into
> > one type that accomplishes the purposes of both types;
> >
> > 1. TopLevelExpr is meant to represent a JSON Object, but only those that
> > represent what qapi-schema calls a TOP-LEVEL-EXPR, i.e. definitions,
> > pragmas, and includes.
> >
> > 2. ParsedExpression is meant to represent a container around the above
> > type, alongside QAPI-specific metadata -- the QAPISourceInfo and QAPIDoc
> > objects.
> >
> > We can actually just roll these up into one type: A python mapping that
> > has the metadata embedded directly inside of it.
>
> On the general idea: yes, please!  Gets rid of "TopLevelExpr and
> _JSONObject are the same, except semantically, but nothing checks that",
> which I never liked.

I prefer them to be checked/enforced too; I'll admit to trying to do
"a little less" to try and invoke less magic, especially in Python
3.6. The best magic comes in later versions.

>
> > NB: This necessitates a change of typing for check_if() and
> > check_keys(), because mypy does not believe UserDict[str, object] ⊆
> > Dict[str, object]. It will, however, accept Mapping or
> > MutableMapping. In this case, the immutable form is preferred as an
> > input parameter because we don't actually mutate the input.
> >
> > Without this change, we will observe:
> > qapi/expr.py:631: error: Argument 1 to "check_keys" has incompatible
> > type "QAPIExpression"; expected "Dict[str, object]"
> >
> > Signed-off-by: John Snow <jsnow@redhat.com>
> > ---
> >  scripts/qapi/expr.py   | 133 +++++++++++++++++++----------------------
> >  scripts/qapi/parser.py |  43 ++++++++-----
> >  scripts/qapi/schema.py | 105 ++++++++++++++++----------------
> >  3 files changed, 142 insertions(+), 139 deletions(-)
> >
> > diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
> > index 95a25758fed..83fa7a85b06 100644
> > --- a/scripts/qapi/expr.py
> > +++ b/scripts/qapi/expr.py
> > @@ -34,9 +34,9 @@
> >  import re
> >  from typing import (
> >      Collection,
> > -    Dict,
> >      Iterable,
> >      List,
> > +    Mapping,
> >      Optional,
> >      Union,
> >      cast,
> > @@ -44,7 +44,7 @@
> >
> >  from .common import c_name
> >  from .error import QAPISemError
> > -from .parser import ParsedExpression, TopLevelExpr
> > +from .parser import QAPIExpression
> >  from .source import QAPISourceInfo
> >
> >
> > @@ -53,7 +53,7 @@
> >  # here (and also not practical as long as mypy lacks recursive
> >  # types), because the purpose of this module is to interrogate that
> >  # type.
> > -_JSONObject = Dict[str, object]
> > +_JSONObject = Mapping[str, object]
> >
> >
> >  # See check_name_str(), below.
> > @@ -229,12 +229,11 @@ def pprint(elems: Iterable[str]) -> str:
> >                 pprint(unknown), pprint(allowed)))
> >
> >
> > -def check_flags(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_flags(expr: QAPIExpression) -> None:
> >      """
> >      Ensure flag members (if present) have valid values.
> >
> > -    :param expr: The `TopLevelExpr` to validate.
> > -    :param info: QAPI schema source file information.
> > +    :param expr: The `QAPIExpression` to validate.
> >
> >      :raise QAPISemError:
> >          When certain flags have an invalid value, or when
> > @@ -243,18 +242,18 @@ def check_flags(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      for key in ('gen', 'success-response'):
> >          if key in expr and expr[key] is not False:
> >              raise QAPISemError(
> > -                info, "flag '%s' may only use false value" % key)
> > +                expr.info, "flag '%s' may only use false value" % key)
> >      for key in ('boxed', 'allow-oob', 'allow-preconfig', 'coroutine'):
> >          if key in expr and expr[key] is not True:
> >              raise QAPISemError(
> > -                info, "flag '%s' may only use true value" % key)
> > +                expr.info, "flag '%s' may only use true value" % key)
> >      if 'allow-oob' in expr and 'coroutine' in expr:
> >          # This is not necessarily a fundamental incompatibility, but
> >          # we don't have a use case and the desired semantics isn't
> >          # obvious.  The simplest solution is to forbid it until we get
> >          # a use case for it.
> > -        raise QAPISemError(info, "flags 'allow-oob' and 'coroutine' "
> > -                                 "are incompatible")
> > +        raise QAPISemError(
> > +            expr.info, "flags 'allow-oob' and 'coroutine' are 
> > incompatible")
> >
> >
> >  def check_if(expr: _JSONObject, info: QAPISourceInfo, source: str) -> None:
> > @@ -447,12 +446,11 @@ def check_features(features: Optional[object],
> >          check_if(feat, info, source)
> >
> >
> > -def check_enum(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_enum(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as an ``enum`` definition.
> > +    Normalize and validate this `QAPIExpression` as an ``enum`` definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: When ``expr`` is not a valid ``enum``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -462,36 +460,35 @@ def check_enum(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      prefix = expr.get('prefix')
> >
> >      if not isinstance(members, list):
> > -        raise QAPISemError(info, "'data' must be an array")
> > +        raise QAPISemError(expr.info, "'data' must be an array")
> >      if prefix is not None and not isinstance(prefix, str):
> > -        raise QAPISemError(info, "'prefix' must be a string")
> > +        raise QAPISemError(expr.info, "'prefix' must be a string")
> >
> > -    permissive = name in info.pragma.member_name_exceptions
> > +    permissive = name in expr.info.pragma.member_name_exceptions
> >
> >      members[:] = [m if isinstance(m, dict) else {'name': m}
> >                    for m in members]
> >      for member in members:
> >          source = "'data' member"
> > -        check_keys(member, info, source, ['name'], ['if', 'features'])
> > +        check_keys(member, expr.info, source, ['name'], ['if', 'features'])
> >          member_name = member['name']
> > -        check_name_is_str(member_name, info, source)
> > +        check_name_is_str(member_name, expr.info, source)
> >          source = "%s '%s'" % (source, member_name)
> >          # Enum members may start with a digit
> >          if member_name[0].isdigit():
> >              member_name = 'd' + member_name  # Hack: hide the digit
> > -        check_name_lower(member_name, info, source,
> > +        check_name_lower(member_name, expr.info, source,
> >                           permit_upper=permissive,
> >                           permit_underscore=permissive)
> > -        check_if(member, info, source)
> > -        check_features(member.get('features'), info)
> > +        check_if(member, expr.info, source)
> > +        check_features(member.get('features'), expr.info)
> >
> >
> > -def check_struct(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_struct(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as a ``struct`` definition.
> > +    Normalize and validate this `QAPIExpression` as a ``struct`` 
> > definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: When ``expr`` is not a valid ``struct``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -499,16 +496,15 @@ def check_struct(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      name = cast(str, expr['struct'])  # Checked in check_exprs
> >      members = expr['data']
> >
> > -    check_type(members, info, "'data'", allow_dict=name)
> > -    check_type(expr.get('base'), info, "'base'")
> > +    check_type(members, expr.info, "'data'", allow_dict=name)
> > +    check_type(expr.get('base'), expr.info, "'base'")
> >
> >
> > -def check_union(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_union(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as a ``union`` definition.
> > +    Normalize and validate this `QAPIExpression` as a ``union`` definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: when ``expr`` is not a valid ``union``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -518,25 +514,24 @@ def check_union(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      discriminator = expr['discriminator']
> >      members = expr['data']
> >
> > -    check_type(base, info, "'base'", allow_dict=name)
> > -    check_name_is_str(discriminator, info, "'discriminator'")
> > +    check_type(base, expr.info, "'base'", allow_dict=name)
> > +    check_name_is_str(discriminator, expr.info, "'discriminator'")
> >
> >      if not isinstance(members, dict):
> > -        raise QAPISemError(info, "'data' must be an object")
> > +        raise QAPISemError(expr.info, "'data' must be an object")
> >
> >      for (key, value) in members.items():
> >          source = "'data' member '%s'" % key
> > -        check_keys(value, info, source, ['type'], ['if'])
> > -        check_if(value, info, source)
> > -        check_type(value['type'], info, source, allow_array=not base)
> > +        check_keys(value, expr.info, source, ['type'], ['if'])
> > +        check_if(value, expr.info, source)
> > +        check_type(value['type'], expr.info, source, allow_array=not base)
> >
> >
> > -def check_alternate(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_alternate(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as an ``alternate`` 
> > definition.
> > +    Normalize and validate a `QAPIExpression` as an ``alternate`` 
> > definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: When ``expr`` is not a valid ``alternate``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -544,25 +539,24 @@ def check_alternate(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      members = expr['data']
> >
> >      if not members:
> > -        raise QAPISemError(info, "'data' must not be empty")
> > +        raise QAPISemError(expr.info, "'data' must not be empty")
> >
> >      if not isinstance(members, dict):
> > -        raise QAPISemError(info, "'data' must be an object")
> > +        raise QAPISemError(expr.info, "'data' must be an object")
> >
> >      for (key, value) in members.items():
> >          source = "'data' member '%s'" % key
> > -        check_name_lower(key, info, source)
> > -        check_keys(value, info, source, ['type'], ['if'])
> > -        check_if(value, info, source)
> > -        check_type(value['type'], info, source, allow_array=True)
> > +        check_name_lower(key, expr.info, source)
> > +        check_keys(value, expr.info, source, ['type'], ['if'])
> > +        check_if(value, expr.info, source)
> > +        check_type(value['type'], expr.info, source, allow_array=True)
> >
> >
> > -def check_command(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_command(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as a ``command`` definition.
> > +    Normalize and validate this `QAPIExpression` as a ``command`` 
> > definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: When ``expr`` is not a valid ``command``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -572,17 +566,16 @@ def check_command(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      boxed = expr.get('boxed', False)
> >
> >      if boxed and args is None:
> > -        raise QAPISemError(info, "'boxed': true requires 'data'")
> > -    check_type(args, info, "'data'", allow_dict=not boxed)
> > -    check_type(rets, info, "'returns'", allow_array=True)
> > +        raise QAPISemError(expr.info, "'boxed': true requires 'data'")
> > +    check_type(args, expr.info, "'data'", allow_dict=not boxed)
> > +    check_type(rets, expr.info, "'returns'", allow_array=True)
> >
> >
> > -def check_event(expr: TopLevelExpr, info: QAPISourceInfo) -> None:
> > +def check_event(expr: QAPIExpression) -> None:
> >      """
> > -    Normalize and validate this `TopLevelExpr` as an ``event`` definition.
> > +    Normalize and validate this `QAPIExpression` as an ``event`` 
> > definition.
> >
> >      :param expr: The expression to validate.
> > -    :param info: QAPI schema source file information.
> >
> >      :raise QAPISemError: When ``expr`` is not a valid ``event``.
> >      :return: None, ``expr`` is normalized in-place as needed.
> > @@ -591,25 +584,23 @@ def check_event(expr: TopLevelExpr, info: 
> > QAPISourceInfo) -> None:
> >      boxed = expr.get('boxed', False)
> >
> >      if boxed and args is None:
> > -        raise QAPISemError(info, "'boxed': true requires 'data'")
> > -    check_type(args, info, "'data'", allow_dict=not boxed)
> > +        raise QAPISemError(expr.info, "'boxed': true requires 'data'")
> > +    check_type(args, expr.info, "'data'", allow_dict=not boxed)
> >
> >
> > -def check_expr(pexpr: ParsedExpression) -> None:
> > +def check_expr(expr: QAPIExpression) -> None:
> >      """
> > -    Validate and normalize a `ParsedExpression`.
> > +    Validate and normalize a `QAPIExpression`.
> >
> > -    :param pexpr: The parsed expression to normalize and validate.
> > +    :param expr: The parsed expression to normalize and validate.
> >
> >      :raise QAPISemError: When this expression fails validation.
> > -    :return: None, ``pexpr`` is normalized in-place as needed.
> > +    :return: None, ``expr`` is normalized in-place as needed.
> >      """
> > -    expr = pexpr.expr
> > -    info = pexpr.info
> > -
> >      if 'include' in expr:
> >          return
> >
> > +    info = expr.info
> >      metas = set(expr.keys() & {
> >          'enum', 'struct', 'union', 'alternate', 'command', 'event'})
> >      if len(metas) != 1:
> > @@ -625,7 +616,7 @@ def check_expr(pexpr: ParsedExpression) -> None:
> >      info.set_defn(meta, name)
> >      check_defn_name_str(name, info, meta)
> >
> > -    doc = pexpr.doc
> > +    doc = expr.doc
> >      if doc:
> >          if doc.symbol != name:
> >              raise QAPISemError(
> > @@ -638,24 +629,24 @@ def check_expr(pexpr: ParsedExpression) -> None:
> >      if meta == 'enum':
> >          check_keys(expr, info, meta,
> >                     ['enum', 'data'], ['if', 'features', 'prefix'])
> > -        check_enum(expr, info)
> > +        check_enum(expr)
> >      elif meta == 'union':
> >          check_keys(expr, info, meta,
> >                     ['union', 'base', 'discriminator', 'data'],
> >                     ['if', 'features'])
> >          normalize_members(expr.get('base'))
> >          normalize_members(expr['data'])
> > -        check_union(expr, info)
> > +        check_union(expr)
> >      elif meta == 'alternate':
> >          check_keys(expr, info, meta,
> >                     ['alternate', 'data'], ['if', 'features'])
> >          normalize_members(expr['data'])
> > -        check_alternate(expr, info)
> > +        check_alternate(expr)
> >      elif meta == 'struct':
> >          check_keys(expr, info, meta,
> >                     ['struct', 'data'], ['base', 'if', 'features'])
> >          normalize_members(expr['data'])
> > -        check_struct(expr, info)
> > +        check_struct(expr)
> >      elif meta == 'command':
> >          check_keys(expr, info, meta,
> >                     ['command'],
> > @@ -663,21 +654,21 @@ def check_expr(pexpr: ParsedExpression) -> None:
> >                      'gen', 'success-response', 'allow-oob',
> >                      'allow-preconfig', 'coroutine'])
> >          normalize_members(expr.get('data'))
> > -        check_command(expr, info)
> > +        check_command(expr)
> >      elif meta == 'event':
> >          check_keys(expr, info, meta,
> >                     ['event'], ['data', 'boxed', 'if', 'features'])
> >          normalize_members(expr.get('data'))
> > -        check_event(expr, info)
> > +        check_event(expr)
> >      else:
> >          assert False, 'unexpected meta type'
> >
> >      check_if(expr, info, meta)
> >      check_features(expr.get('features'), info)
> > -    check_flags(expr, info)
> > +    check_flags(expr)
> >
> >
> > -def check_exprs(exprs: List[ParsedExpression]) -> List[ParsedExpression]:
> > +def check_exprs(exprs: List[QAPIExpression]) -> List[QAPIExpression]:
> >      """
> >      Validate and normalize a list of parsed QAPI schema expressions.
> >
> > diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
> > index f897dffbfd4..88f6fdfa67b 100644
> > --- a/scripts/qapi/parser.py
> > +++ b/scripts/qapi/parser.py
> > @@ -14,14 +14,14 @@
> >  # This work is licensed under the terms of the GNU GPL, version 2.
> >  # See the COPYING file in the top-level directory.
> >
> > -from collections import OrderedDict
> > +from collections import OrderedDict, UserDict
> >  import os
> >  import re
> >  from typing import (
> >      TYPE_CHECKING,
> >      Dict,
> >      List,
> > -    NamedTuple,
> > +    Mapping,
> >      Optional,
> >      Set,
> >      Union,
> > @@ -38,21 +38,32 @@
> >      from .schema import QAPISchemaFeature, QAPISchemaMember
> >
> >
> > -#: Represents a single Top Level QAPI schema expression.
> > -TopLevelExpr = Dict[str, object]
> > -
> >  # Return value alias for get_expr().
> >  _ExprValue = Union[List[object], Dict[str, object], str, bool]
> >
> > -# FIXME: Consolidate and centralize definitions for TopLevelExpr,
> > -# _ExprValue, _JSONValue, and _JSONObject; currently scattered across
> > -# several modules.
> >
> > +# FIXME: Consolidate and centralize definitions for _ExprValue,
> > +# JSONValue, and _JSONObject; currently scattered across several
> > +# modules.
> >
> > -class ParsedExpression(NamedTuple):
> > -    expr: TopLevelExpr
> > -    info: QAPISourceInfo
> > -    doc: Optional['QAPIDoc']
> > +
> > +# 3.6 workaround: can be removed when Python 3.7+ is our required version.
> > +if TYPE_CHECKING:
> > +    _UserDict = UserDict[str, object]
> > +else:
> > +    _UserDict = UserDict
>
> Worth mentioning in the commit message?  Genuine question; I'm not sure
> :)
>

If you please! My only consideration here was leaving a comment with
both "3.6" and "3.7" so that when I git grep to upgrade from 3.6 to
3.7, there's a shining spotlight on this particular wart.

The problem here is that Python 3.6 does not believe that you can
subscript UserDict, because UserDict is not generic in its
*implementation*, it's only generic in its type stub. Short-sighted
problem that was corrected for 3.7; here's a bug filed by Papa Guido
heself: https://github.com/python/typing/issues/60

(This bug is where I found this workaround from.)

> > +
> > +
> > +class QAPIExpression(_UserDict):
> > +    def __init__(
> > +        self,
> > +        initialdata: Mapping[str, object],
>
> I'd prefer to separate words: initial_data.
>

Wasn't my choice:
https://docs.python.org/3/library/collections.html#collections.UserDict

> > +        info: QAPISourceInfo,
> > +        doc: Optional['QAPIDoc'] = None,
> > +    ):
> > +        super().__init__(initialdata)
> > +        self.info = info
> > +        self.doc: Optional['QAPIDoc'] = doc
> >
> >
> >  class QAPIParseError(QAPISourceError):
> > @@ -107,7 +118,7 @@ def __init__(self,
> >          self.line_pos = 0
> >
> >          # Parser output:
> > -        self.exprs: List[ParsedExpression] = []
> > +        self.exprs: List[QAPIExpression] = []
> >          self.docs: List[QAPIDoc] = []
> >
> >          # Showtime!
> > @@ -178,10 +189,10 @@ def _parse(self) -> None:
> >              cur_doc = None
> >          self.reject_expr_doc(cur_doc)
> >
> > -    def _add_expr(self, expr: TopLevelExpr,
> > +    def _add_expr(self, expr: Mapping[str, object],
> >                    info: QAPISourceInfo,
> >                    doc: Optional['QAPIDoc'] = None) -> None:
> > -        self.exprs.append(ParsedExpression(expr, info, doc))
> > +        self.exprs.append(QAPIExpression(expr, info, doc))
> >
> >      @staticmethod
> >      def reject_expr_doc(doc: Optional['QAPIDoc']) -> None:
> > @@ -791,7 +802,7 @@ def connect_feature(self, feature: 'QAPISchemaFeature') 
> > -> None:
> >                                 % feature.name)
> >          self.features[feature.name].connect(feature)
> >
> > -    def check_expr(self, expr: TopLevelExpr) -> None:
> > +    def check_expr(self, expr: QAPIExpression) -> None:
> >          if self.has_section('Returns') and 'command' not in expr:
> >              raise QAPISemError(self.info,
> >                                 "'Returns:' is only valid for commands")
> > diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
> > index 89f8e60db36..295c21eab22 100644
> > --- a/scripts/qapi/schema.py
> > +++ b/scripts/qapi/schema.py
> > @@ -17,7 +17,7 @@
> >  from collections import OrderedDict
> >  import os
> >  import re
> > -from typing import Optional
> > +from typing import List, Optional
> >
> >  from .common import (
> >      POINTER_SUFFIX,
> > @@ -29,7 +29,7 @@
> >  )
> >  from .error import QAPIError, QAPISemError, QAPISourceError
> >  from .expr import check_exprs
> > -from .parser import QAPISchemaParser
> > +from .parser import QAPIExpression, QAPISchemaParser
> >
> >
> >  class QAPISchemaIfCond:
> > @@ -964,10 +964,11 @@ def module_by_fname(self, fname):
> >          name = self._module_name(fname)
> >          return self._module_dict[name]
> >
> > -    def _def_include(self, expr, info, doc):
> > +    def _def_include(self, expr: QAPIExpression):
> >          include = expr['include']
> > -        assert doc is None
> > -        self._def_entity(QAPISchemaInclude(self._make_module(include), 
> > info))
> > +        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_entity(QAPISchemaBuiltinType(name, json_type, c_type))
> > @@ -1045,15 +1046,15 @@ def _make_implicit_object_type(self, name, info, 
> > ifcond, role, members):
> >                  name, info, None, ifcond, None, None, members, None))
> >          return name
> >
> > -    def _def_enum_type(self, expr, info, doc):
> > +    def _def_enum_type(self, expr: QAPIExpression):
> >          name = expr['enum']
> >          data = expr['data']
> >          prefix = expr.get('prefix')
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          self._def_entity(QAPISchemaEnumType(
> > -            name, info, doc, ifcond, features,
> > -            self._make_enum_members(data, info), prefix))
> > +            name, expr.info, expr.doc, ifcond, features,
> > +            self._make_enum_members(data, expr.info), prefix))
> >
> >      def _make_member(self, name, typ, ifcond, features, info):
> >          optional = False
> > @@ -1072,15 +1073,15 @@ def _make_members(self, data, info):
> >                                    value.get('features'), info)
> >                  for (key, value) in data.items()]
> >
> > -    def _def_struct_type(self, expr, info, doc):
> > +    def _def_struct_type(self, expr: QAPIExpression):
> >          name = expr['struct']
> >          base = expr.get('base')
> >          data = expr['data']
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          self._def_entity(QAPISchemaObjectType(
> > -            name, info, doc, ifcond, features, base,
> > -            self._make_members(data, info),
> > +            name, expr.info, expr.doc, ifcond, features, base,
> > +            self._make_members(data, expr.info),
> >              None))
> >
> >      def _make_variant(self, case, typ, ifcond, info):
> > @@ -1089,46 +1090,49 @@ def _make_variant(self, case, typ, ifcond, info):
> >              typ = self._make_array_type(typ[0], info)
> >          return QAPISchemaVariant(case, info, typ, ifcond)
> >
> > -    def _def_union_type(self, expr, info, doc):
> > +    def _def_union_type(self, expr: QAPIExpression):
> >          name = expr['union']
> >          base = expr['base']
> >          tag_name = expr['discriminator']
> >          data = expr['data']
> > +        assert isinstance(data, dict)
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          if isinstance(base, dict):
> >              base = self._make_implicit_object_type(
> > -                name, info, ifcond,
> > -                'base', self._make_members(base, info))
> > +                name, expr.info, ifcond,
> > +                'base', self._make_members(base, expr.info))
> >          variants = [
> >              self._make_variant(key, value['type'],
> >                                 QAPISchemaIfCond(value.get('if')),
> > -                               info)
> > +                               expr.info)
> >              for (key, value) in data.items()]
> > -        members = []
> > +        members: List[QAPISchemaObjectTypeMember] = []
> >          self._def_entity(
> > -            QAPISchemaObjectType(name, info, doc, ifcond, features,
> > +            QAPISchemaObjectType(name, expr.info, expr.doc, ifcond, 
> > features,
> >                                   base, members,
> >                                   QAPISchemaVariants(
> > -                                     tag_name, info, None, variants)))
> > +                                     tag_name, expr.info, None, variants)))
> >
> > -    def _def_alternate_type(self, expr, info, doc):
> > +    def _def_alternate_type(self, expr: QAPIExpression):
> >          name = expr['alternate']
> >          data = expr['data']
> > +        assert isinstance(data, dict)
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          variants = [
> >              self._make_variant(key, value['type'],
> >                                 QAPISchemaIfCond(value.get('if')),
> > -                               info)
> > +                               expr.info)
> >              for (key, value) in data.items()]
> > -        tag_member = QAPISchemaObjectTypeMember('type', info, 'QType', 
> > False)
> > +        tag_member = QAPISchemaObjectTypeMember(
> > +            'type', expr.info, 'QType', False)
> >          self._def_entity(
> > -            QAPISchemaAlternateType(name, info, doc, ifcond, features,
> > -                                    QAPISchemaVariants(
> > -                                        None, info, tag_member, variants)))
> > +            QAPISchemaAlternateType(
> > +                name, expr.info, expr.doc, ifcond, features,
> > +                QAPISchemaVariants(None, expr.info, tag_member, variants)))
> >
> > -    def _def_command(self, expr, info, doc):
> > +    def _def_command(self, expr: QAPIExpression):
> >          name = expr['command']
> >          data = expr.get('data')
> >          rets = expr.get('returns')
> > @@ -1139,52 +1143,49 @@ def _def_command(self, expr, info, doc):
> >          allow_preconfig = expr.get('allow-preconfig', False)
> >          coroutine = expr.get('coroutine', False)
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          if isinstance(data, OrderedDict):
> >              data = self._make_implicit_object_type(
> > -                name, info, ifcond,
> > -                'arg', self._make_members(data, info))
> > +                name, expr.info, ifcond,
> > +                'arg', self._make_members(data, expr.info))
> >          if isinstance(rets, list):
> >              assert len(rets) == 1
> > -            rets = self._make_array_type(rets[0], info)
> > -        self._def_entity(QAPISchemaCommand(name, info, doc, ifcond, 
> > features,
> > -                                           data, rets,
> > +            rets = self._make_array_type(rets[0], expr.info)
> > +        self._def_entity(QAPISchemaCommand(name, expr.info, expr.doc, 
> > ifcond,
> > +                                           features, data, rets,
> >                                             gen, success_response,
> >                                             boxed, allow_oob, 
> > allow_preconfig,
> >                                             coroutine))
> >
> > -    def _def_event(self, expr, info, doc):
> > +    def _def_event(self, expr: QAPIExpression):
> >          name = expr['event']
> >          data = expr.get('data')
> >          boxed = expr.get('boxed', False)
> >          ifcond = QAPISchemaIfCond(expr.get('if'))
> > -        features = self._make_features(expr.get('features'), info)
> > +        features = self._make_features(expr.get('features'), expr.info)
> >          if isinstance(data, OrderedDict):
> >              data = self._make_implicit_object_type(
> > -                name, info, ifcond,
> > -                'arg', self._make_members(data, info))
> > -        self._def_entity(QAPISchemaEvent(name, info, doc, ifcond, features,
> > -                                         data, boxed))
> > +                name, expr.info, ifcond,
> > +                'arg', self._make_members(data, expr.info))
> > +        self._def_entity(QAPISchemaEvent(name, expr.info, expr.doc, ifcond,
> > +                                         features, data, boxed))
> >
> >      def _def_exprs(self, exprs):
> > -        for expr_elem in exprs:
> > -            expr = expr_elem.expr
> > -            info = expr_elem.info
> > -            doc = expr_elem.doc
> > +        for expr in exprs:
> >              if 'enum' in expr:
> > -                self._def_enum_type(expr, info, doc)
> > +                self._def_enum_type(expr)
> >              elif 'struct' in expr:
> > -                self._def_struct_type(expr, info, doc)
> > +                self._def_struct_type(expr)
> >              elif 'union' in expr:
> > -                self._def_union_type(expr, info, doc)
> > +                self._def_union_type(expr)
> >              elif 'alternate' in expr:
> > -                self._def_alternate_type(expr, info, doc)
> > +                self._def_alternate_type(expr)
> >              elif 'command' in expr:
> > -                self._def_command(expr, info, doc)
> > +                self._def_command(expr)
> >              elif 'event' in expr:
> > -                self._def_event(expr, info, doc)
> > +                self._def_event(expr)
> >              elif 'include' in expr:
> > -                self._def_include(expr, info, doc)
> > +                self._def_include(expr)
> >              else:
> >                  assert False
>
> The insertion of expr. makes the patch a bit tiresome to review.  I
> only skimmed it for now.

There's indeed a lot of mechanical churn. It appears to work via
testing; both make check and the full CI job.
"It compiles, how wrong could it be!?"

*ducks*

--js