qapi/introspect.py: add type hint annotations

NB: The type aliases (SchemaInfo et al) declare intent for some of the
"dictly-typed" objects we pass around in introspect.py. They do not
enforce the shape of those objects, and cannot, until Python 3.7 or
later. (And even then, it may not be "worth it".)

Annotations are also added to the QAPISchemaEntity __init__ method in
schema.py to allow mypy to statically prove the type of typ.name,
needed to prove the return type of
QAPISchemaGenIntrospectVisitor._use_type().

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210216021809.134886-15-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Note on QAPISchemaEntity.__init__() squashed into commit message,
Comment wrapped to conform to PEP 8]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

3 files changed, 93 insertions, 39 deletions

diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
index da7bc88..05c1a19 100644
--- a/scripts/qapi/introspect.py
+++ b/scripts/qapi/introspect.py
@@ -17,6 +17,7 @@ from typing import (
     Iterable,
     List,
     Optional,
+    Sequence,
     Tuple,
     TypeVar,
     Union,
@@ -30,10 +31,19 @@ from .common import (
 )
 from .gen import QAPISchemaMonolithicCVisitor
 from .schema import (
+    QAPISchema,
     QAPISchemaArrayType,
     QAPISchemaBuiltinType,
+    QAPISchemaEntity,
+    QAPISchemaEnumMember,
+    QAPISchemaFeature,
+    QAPISchemaObjectType,
+    QAPISchemaObjectTypeMember,
     QAPISchemaType,
+    QAPISchemaVariant,
+    QAPISchemaVariants,
 )
+from .source import QAPISourceInfo
 
 
 # This module constructs a tree data structure that is used to
@@ -58,6 +68,16 @@ _NonScalar = Union[Dict[str, _Stub], List[_Stub]]
 _Value = Union[_Scalar, _NonScalar]
 JSONValue = Union[_Value, 'Annotated[_Value]']
 
+# These types are based on structures defined in QEMU's schema, so we
+# lack precise types for them here. Python 3.6 does not offer
+# TypedDict constructs, so they are broadly typed here as simple
+# Python Dicts.
+SchemaInfo = Dict[str, object]
+SchemaInfoObject = Dict[str, object]
+SchemaInfoObjectVariant = Dict[str, object]
+SchemaInfoObjectMember = Dict[str, object]
+SchemaInfoCommand = Dict[str, object]
+
 
 _ValueT = TypeVar('_ValueT', bound=_Value)
 
@@ -77,9 +97,11 @@ class Annotated(Generic[_ValueT]):
         self.ifcond: Tuple[str, ...] = tuple(ifcond)
 
 
-def _tree_to_qlit(obj, level=0, dict_value=False):
+def _tree_to_qlit(obj: JSONValue,
+                  level: int = 0,
+                  dict_value: bool = False) -> str:
 
-    def indent(level):
+    def indent(level: int) -> str:
         return level * 4 * ' '
 
     if isinstance(obj, Annotated):
@@ -137,21 +159,21 @@ def _tree_to_qlit(obj, level=0, dict_value=False):
     return ret
 
 
-def to_c_string(string):
+def to_c_string(string: str) -> str:
     return '"' + string.replace('\\', r'\\').replace('"', r'\"') + '"'
 
 
 class QAPISchemaGenIntrospectVisitor(QAPISchemaMonolithicCVisitor):
 
-    def __init__(self, prefix, unmask):
+    def __init__(self, prefix: str, unmask: bool):
         super().__init__(
             prefix, 'qapi-introspect',
             ' * QAPI/QMP schema introspection', __doc__)
         self._unmask = unmask
-        self._schema = None
-        self._trees = []
-        self._used_types = []
-        self._name_map = {}
+        self._schema: Optional[QAPISchema] = None
+        self._trees: List[Annotated[SchemaInfo]] = []
+        self._used_types: List[QAPISchemaType] = []
+        self._name_map: Dict[str, str] = {}
         self._genc.add(mcgen('''
 #include "qemu/osdep.h"
 #include "%(prefix)sqapi-introspect.h"
@@ -159,10 +181,10 @@ class QAPISchemaGenIntrospectVisitor(QAPISchemaMonolithicCVisitor):
 ''',
                              prefix=prefix))
 
-    def visit_begin(self, schema):
+    def visit_begin(self, schema: QAPISchema) -> None:
         self._schema = schema
 
-    def visit_end(self):
+    def visit_end(self) -> None:
         # visit the types that are actually used
         for typ in self._used_types:
             typ.visit(self)
@@ -184,18 +206,18 @@ const QLitObject %(c_name)s = %(c_string)s;
         self._used_types = []
         self._name_map = {}
 
-    def visit_needed(self, entity):
+    def visit_needed(self, entity: QAPISchemaEntity) -> bool:
         # Ignore types on first pass; visit_end() will pick up used types
         return not isinstance(entity, QAPISchemaType)
 
-    def _name(self, name):
+    def _name(self, name: str) -> str:
         if self._unmask:
             return name
         if name not in self._name_map:
             self._name_map[name] = '%d' % len(self._name_map)
         return self._name_map[name]
 
-    def _use_type(self, typ):
+    def _use_type(self, typ: QAPISchemaType) -> str:
         assert self._schema is not None
 
         # Map the various integer types to plain int
@@ -217,10 +239,13 @@ const QLitObject %(c_name)s = %(c_string)s;
         return self._name(typ.name)
 
     @staticmethod
-    def _gen_features(features):
+    def _gen_features(features: List[QAPISchemaFeature]
+                      ) -> List[Annotated[str]]:
         return [Annotated(f.name, f.ifcond) for f in features]
 
-    def _gen_tree(self, name, mtype, obj, ifcond, features):
+    def _gen_tree(self, name: str, mtype: str, obj: Dict[str, object],
+                  ifcond: Sequence[str],
+                  features: Optional[List[QAPISchemaFeature]]) -> None:
         comment: Optional[str] = None
         if mtype not in ('command', 'event', 'builtin', 'array'):
             if not self._unmask:
@@ -234,42 +259,65 @@ const QLitObject %(c_name)s = %(c_string)s;
             obj['features'] = self._gen_features(features)
         self._trees.append(Annotated(obj, ifcond, comment))
 
-    def _gen_member(self, member):
-        obj = {'name': member.name, 'type': self._use_type(member.type)}
+    def _gen_member(self, member: QAPISchemaObjectTypeMember
+                    ) -> Annotated[SchemaInfoObjectMember]:
+        obj: SchemaInfoObjectMember = {
+            'name': member.name,
+            'type': self._use_type(member.type)
+        }
         if member.optional:
             obj['default'] = None
         if member.features:
             obj['features'] = self._gen_features(member.features)
         return Annotated(obj, member.ifcond)
 
-    def _gen_variant(self, variant):
-        obj = {'case': variant.name, 'type': self._use_type(variant.type)}
+    def _gen_variant(self, variant: QAPISchemaVariant
+                     ) -> Annotated[SchemaInfoObjectVariant]:
+        obj: SchemaInfoObjectVariant = {
+            'case': variant.name,
+            'type': self._use_type(variant.type)
+        }
         return Annotated(obj, variant.ifcond)
 
-    def visit_builtin_type(self, name, info, json_type):
+    def visit_builtin_type(self, name: str, info: Optional[QAPISourceInfo],
+                           json_type: str) -> None:
         self._gen_tree(name, 'builtin', {'json-type': json_type}, [], None)
 
-    def visit_enum_type(self, name, info, ifcond, features, members, prefix):
+    def visit_enum_type(self, name: str, info: Optional[QAPISourceInfo],
+                        ifcond: Sequence[str],
+                        features: List[QAPISchemaFeature],
+                        members: List[QAPISchemaEnumMember],
+                        prefix: Optional[str]) -> None:
         self._gen_tree(
             name, 'enum',
             {'values': [Annotated(m.name, m.ifcond) for m in members]},
             ifcond, features
         )
 
-    def visit_array_type(self, name, info, ifcond, element_type):
+    def visit_array_type(self, name: str, info: Optional[QAPISourceInfo],
+                         ifcond: Sequence[str],
+                         element_type: QAPISchemaType) -> None:
         element = self._use_type(element_type)
         self._gen_tree('[' + element + ']', 'array', {'element-type': element},
                        ifcond, None)
 
-    def visit_object_type_flat(self, name, info, ifcond, features,
-                               members, variants):
-        obj = {'members': [self._gen_member(m) for m in members]}
+    def visit_object_type_flat(self, name: str, info: Optional[QAPISourceInfo],
+                               ifcond: Sequence[str],
+                               features: List[QAPISchemaFeature],
+                               members: List[QAPISchemaObjectTypeMember],
+                               variants: Optional[QAPISchemaVariants]) -> None:
+        obj: SchemaInfoObject = {
+            'members': [self._gen_member(m) for m in members]
+        }
         if variants:
             obj['tag'] = variants.tag_member.name
             obj['variants'] = [self._gen_variant(v) for v in variants.variants]
         self._gen_tree(name, 'object', obj, ifcond, features)
 
-    def visit_alternate_type(self, name, info, ifcond, features, variants):
+    def visit_alternate_type(self, name: str, info: Optional[QAPISourceInfo],
+                             ifcond: Sequence[str],
+                             features: List[QAPISchemaFeature],
+                             variants: QAPISchemaVariants) -> None:
         self._gen_tree(
             name, 'alternate',
             {'members': [Annotated({'type': self._use_type(m.type)},
@@ -278,27 +326,38 @@ const QLitObject %(c_name)s = %(c_string)s;
             ifcond, features
         )
 
-    def visit_command(self, name, info, ifcond, features,
-                      arg_type, ret_type, gen, success_response, boxed,
-                      allow_oob, allow_preconfig, coroutine):
+    def visit_command(self, name: str, info: Optional[QAPISourceInfo],
+                      ifcond: Sequence[str],
+                      features: List[QAPISchemaFeature],
+                      arg_type: Optional[QAPISchemaObjectType],
+                      ret_type: Optional[QAPISchemaType], gen: bool,
+                      success_response: bool, boxed: bool, allow_oob: bool,
+                      allow_preconfig: bool, coroutine: bool) -> None:
         assert self._schema is not None
 
         arg_type = arg_type or self._schema.the_empty_object_type
         ret_type = ret_type or self._schema.the_empty_object_type
-        obj = {'arg-type': self._use_type(arg_type),
-               'ret-type': self._use_type(ret_type)}
+        obj: SchemaInfoCommand = {
+            'arg-type': self._use_type(arg_type),
+            'ret-type': self._use_type(ret_type)
+        }
         if allow_oob:
             obj['allow-oob'] = allow_oob
         self._gen_tree(name, 'command', obj, ifcond, features)
 
-    def visit_event(self, name, info, ifcond, features, arg_type, boxed):
+    def visit_event(self, name: str, info: Optional[QAPISourceInfo],
+                    ifcond: Sequence[str], features: List[QAPISchemaFeature],
+                    arg_type: Optional[QAPISchemaObjectType],
+                    boxed: bool) -> None:
         assert self._schema is not None
+
         arg_type = arg_type or self._schema.the_empty_object_type
         self._gen_tree(name, 'event', {'arg-type': self._use_type(arg_type)},
                        ifcond, features)
 
 
-def gen_introspect(schema, output_dir, prefix, opt_unmask):
+def gen_introspect(schema: QAPISchema, output_dir: str, prefix: str,
+                   opt_unmask: bool) -> None:
     vis = QAPISchemaGenIntrospectVisitor(prefix, opt_unmask)
     schema.visit(vis)
     vis.write(output_dir)
diff --git a/scripts/qapi/mypy.ini b/scripts/qapi/mypy.ini
index 04bd5db..0a000d5 100644
--- a/scripts/qapi/mypy.ini
+++ b/scripts/qapi/mypy.ini
@@ -13,11 +13,6 @@ disallow_untyped_defs = False
 disallow_incomplete_defs = False
 check_untyped_defs = False
 
-[mypy-qapi.introspect]
-disallow_untyped_defs = False
-disallow_incomplete_defs = False
-check_untyped_defs = False
-
 [mypy-qapi.parser]
 disallow_untyped_defs = False
 disallow_incomplete_defs = False
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 353e802..ff16578 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -28,7 +28,7 @@ from .parser import QAPISchemaParser
 class QAPISchemaEntity:
     meta: Optional[str] = None
 
-    def __init__(self, name, info, doc, ifcond=None, features=None):
+    def __init__(self, name: str, info, doc, ifcond=None, features=None):
         assert name is None or isinstance(name, str)
         for f in features or []:
             assert isinstance(f, QAPISchemaFeature)