docs: use future annotations for genrefman types in typing_extensions

And in fact *use* typing_extensions, which is sometimes the only way to
get access to TypedDict.

Mostly, reindent almost but not quite an entire file to only define
annotation classes under TYPE_CHECKING.

docs/refman/generatorjson.py

@@ -1,5 +1,6 @@
 # SPDX-License-Identifer: Apache-2.0
 # Copyright 2021 The Meson development team
+from __future__ import annotations
 
 from pathlib import Path
 import json

docs/refman/jsonschema.py

@@ -10,79 +10,82 @@ import typing as T
 VERSION_MAJOR = 1  # Changes here indicate breaking format changes (changes to existing keys)
 VERSION_MINOR = 1  # Changes here indicate non-breaking changes (only new keys are added to the existing structure)
 
-class BaseObject(T.TypedDict):
-    '''
-        Base object for most dicts in the JSON doc.
+if T.TYPE_CHECKING:
+    from typing_extensions import TypedDict
 
-        All objects inheriting from BaseObject will support
-        the keys specified here:
-    '''
-    name:        str
-    description: str
-    since:       T.Optional[str]
-    deprecated:  T.Optional[str]
-    notes:       T.List[str]
-    warnings:    T.List[str]
+    class BaseObject(TypedDict):
+        '''
+            Base object for most dicts in the JSON doc.
 
-class Type(T.TypedDict):
-    obj:   str                 # References an object from `root.objects`
-    holds: T.Sequence[object]  # Mypy does not support recursive dicts, but this should be T.List[Type]...
+            All objects inheriting from BaseObject will support
+            the keys specified here:
+        '''
+        name:        str
+        description: str
+        since:       T.Optional[str]
+        deprecated:  T.Optional[str]
+        notes:       T.List[str]
+        warnings:    T.List[str]
 
-class Argument(BaseObject):
-    '''
-        Object that represents any type of a single function or method argument.
-    '''
-    type:        T.List[Type]  # A non-empty list of types that are supported.
-    type_str:    str           # Formatted version of `type`. Is guaranteed to not contain any whitespaces.
-    required:    bool
-    default:     T.Optional[str]
-    min_varargs: T.Optional[int]  # Only relevant for varargs, must be `null` for all other types of arguments
-    max_varargs: T.Optional[int]  # Only relevant for varargs, must be `null` for all other types of arguments
+    class Type(TypedDict):
+        obj:   str                 # References an object from `root.objects`
+        holds: T.Sequence[object]  # Mypy does not support recursive dicts, but this should be T.List[Type]...
 
-class Function(BaseObject):
-    '''
-        Represents a function or method.
-    '''
-    returns:        T.List[Type]  # A non-empty list of types that are supported.
-    returns_str:    str           # Formatted version of `returns`. Is guaranteed to not contain any whitespaces.
-    example:        T.Optional[str]
-    posargs:        T.Dict[str, Argument]
-    optargs:        T.Dict[str, Argument]
-    kwargs:         T.Dict[str, Argument]
-    varargs:        T.Optional[Argument]
-    arg_flattening: bool
+    class Argument(BaseObject):
+        '''
+            Object that represents any type of a single function or method argument.
+        '''
+        type:        T.List[Type]  # A non-empty list of types that are supported.
+        type_str:    str           # Formatted version of `type`. Is guaranteed to not contain any whitespaces.
+        required:    bool
+        default:     T.Optional[str]
+        min_varargs: T.Optional[int]  # Only relevant for varargs, must be `null` for all other types of arguments
+        max_varargs: T.Optional[int]  # Only relevant for varargs, must be `null` for all other types of arguments
 
-class Object(BaseObject):
-    '''
-        Represents all types of Meson objects. The specific object type is stored in the `object_type` field.
-    '''
-    example:           T.Optional[str]
-    object_type:       str                    # Defines the object type: Must be one of: ELEMENTARY, BUILTIN, MODULE, RETURNED
-    methods:           T.Dict[str, Function]
-    is_container:      bool
-    extends:           T.Optional[str]
-    returned_by:       T.List[str]
-    extended_by:       T.List[str]
-    defined_by_module: T.Optional[str]
+    class Function(BaseObject):
+        '''
+            Represents a function or method.
+        '''
+        returns:        T.List[Type]  # A non-empty list of types that are supported.
+        returns_str:    str           # Formatted version of `returns`. Is guaranteed to not contain any whitespaces.
+        example:        T.Optional[str]
+        posargs:        T.Dict[str, Argument]
+        optargs:        T.Dict[str, Argument]
+        kwargs:         T.Dict[str, Argument]
+        varargs:        T.Optional[Argument]
+        arg_flattening: bool
 
-class ObjectsByType(T.TypedDict):
-    '''
-        References to other objects are stored here for ease of navigation / filtering
-    '''
-    elementary: T.List[str]
-    builtins:   T.List[str]
-    returned:   T.List[str]
-    modules:    T.Dict[str, T.List[str]]
+    class Object(BaseObject):
+        '''
+            Represents all types of Meson objects. The specific object type is stored in the `object_type` field.
+        '''
+        example:           T.Optional[str]
+        object_type:       str                    # Defines the object type: Must be one of: ELEMENTARY, BUILTIN, MODULE, RETURNED
+        methods:           T.Dict[str, Function]
+        is_container:      bool
+        extends:           T.Optional[str]
+        returned_by:       T.List[str]
+        extended_by:       T.List[str]
+        defined_by_module: T.Optional[str]
 
+    class ObjectsByType(TypedDict):
+        '''
+            References to other objects are stored here for ease of navigation / filtering
+        '''
+        elementary: T.List[str]
+        builtins:   T.List[str]
+        returned:   T.List[str]
+        modules:    T.Dict[str, T.List[str]]
 
 
-class Root(T.TypedDict):
-    '''
-        The root object of the JSON reference manual
-    '''
-    version_major:   int # See the description above for
-    version_minor:   int # VERSION_MAJOR and VERSION_MINOR
-    meson_version:   str
-    functions:       T.Dict[str, Function]  # A mapping of <name> to a `Function` object for *all* Meson functions
-    objects:         T.Dict[str, Object]    # A mapping of <name> to a `Object`   object for *all* Meson objects (including modules, elementary, etc.)
-    objects_by_type: ObjectsByType
+
+    class Root(TypedDict):
+        '''
+            The root object of the JSON reference manual
+        '''
+        version_major:   int # See the description above for
+        version_minor:   int # VERSION_MAJOR and VERSION_MINOR
+        meson_version:   str
+        functions:       T.Dict[str, Function]  # A mapping of <name> to a `Function` object for *all* Meson functions
+        objects:         T.Dict[str, Object]    # A mapping of <name> to a `Object`   object for *all* Meson objects (including modules, elementary, etc.)
+        objects_by_type: ObjectsByType