feat/stubgen: add const and generic support

src/capnp_stubgen/gen_const.py

@@ -0,0 +1,153 @@
+"""Constant type stub generation.
+
+Handles Cap'n Proto constants declared at file scope or nested within
+structs. Primitive values are rendered inline; complex values (struct,
+list) use ``...`` as a placeholder.
+"""
+
+from __future__ import annotations
+
+import math
+from typing import TYPE_CHECKING
+
+from .type_resolver import resolve_type
+from .utils import type_id_to_int
+
+if TYPE_CHECKING:
+    from .emitter import Emitter
+    from .models import TypeInfo, TypeRegistry
+
+
+def generate_const(
+    emitter: Emitter,
+    type_info: TypeInfo,
+    registry: TypeRegistry,
+) -> None:
+    """Generate a typed constant annotation.
+
+    Example outputs::
+
+        globalInt: int = 12345
+        globalText: str = "foobar"
+        voidConst: None = None
+    """
+    node: dict = type_info.node
+    const_body: dict = node.get("const", {})
+    type_dict: dict = const_body.get("type", {})
+    value_dict: dict = const_body.get("value", {})
+
+    python_type_str = _resolve_const_type(type_dict, registry)
+    python_value_str = _render_const_value(value_dict, type_dict, registry)
+
+    emitter.add_field(
+        type_info.name,
+        python_type_str,
+        default=python_value_str,
+    )
+
+
+# ── type resolution ────────────────────────────────────────────────────────
+
+
+def _resolve_const_type(type_dict: dict, registry: TypeRegistry) -> str:
+    """Resolve a constant's type to a Python type annotation string."""
+    # Handle enum references
+    if "enum" in type_dict:
+        type_id = type_id_to_int(type_dict["enum"]["typeId"])
+        info = registry.get(type_id)
+        if info is not None:
+            return info.scoped_name
+        return "Any"
+
+    # Handle struct references (for struct constants we skip the value)
+    if "struct" in type_dict:
+        type_id = type_id_to_int(type_dict["struct"]["typeId"])
+        info = registry.get(type_id)
+        if info is not None:
+            return info.scoped_name
+        return "Any"
+
+    # Handle list types
+    if "list" in type_dict:
+        return "Any"  # Simplified for now
+
+    # Primitives
+    pt = resolve_type(type_dict, registry)
+    if pt is not None:
+        return pt.render()
+
+    return "Any"
+
+
+# ── value rendering ─────────────────────────────────────────────────────────
+
+
+def _render_const_value(
+    value_dict: dict,
+    type_dict: dict,
+    registry: TypeRegistry,
+) -> str:
+    """Render a constant's value as a Python literal."""
+
+    # Void
+    if "void" in value_dict:
+        return "None"
+
+    # Bool
+    if "bool" in value_dict:
+        return str(value_dict["bool"])
+
+    # Integers (signed and unsigned)
+    for ik in ("int8", "int16", "int32", "int64",
+               "uint8", "uint16", "uint32", "uint64"):
+        if ik in value_dict:
+            return str(value_dict[ik])
+
+    # Floats
+    if "float32" in value_dict or "float64" in value_dict:
+        key = "float32" if "float32" in value_dict else "float64"
+        v = value_dict[key]
+        if math.isinf(v):
+            return "float('inf')" if v > 0 else "float('-inf')"
+        if math.isnan(v):
+            return "float('nan')"
+        return repr(v)
+
+    # Text
+    if "text" in value_dict:
+        return repr(value_dict["text"])
+
+    # Data
+    if "data" in value_dict:
+        return repr(value_dict["data"])
+
+    # Enum
+    if "enum" in value_dict:
+        ordinal = value_dict["enum"]
+        return _resolve_enum_value(type_dict, ordinal, registry)
+
+    # Struct / List / AnyPointer — use placeholder
+    return "..."
+
+
+def _resolve_enum_value(
+    type_dict: dict,
+    ordinal: int,
+    registry: TypeRegistry,
+) -> str:
+    """Resolve an enum ordinal to its enumerant name."""
+    if "enum" not in type_dict:
+        return repr(ordinal)
+
+    type_id = type_id_to_int(type_dict["enum"]["typeId"])
+    info = registry.get(type_id)
+    if info is None:
+        return repr(ordinal)
+
+    enum_node: dict = info.node
+    for e in enum_node.get("enum", {}).get("enumerants", []):
+        if e.get("ordinal") == ordinal or e.get("codeOrder") == ordinal:
+            return f'"{e["name"]}"'
+
+    # Not found — return ordinal as fallback
+    return repr(ordinal)

src/capnp_stubgen/gen_generic.py

@@ -0,0 +1,72 @@
+"""Generic type support.
+
+Handles Cap'n Proto generic (parameterized) structs by generating
+``TypeVar`` declarations and ``Generic[T]`` base classes in Python stubs.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from .emitter import Emitter
+    from .models import TypeInfo, TypeRegistry
+
+
+def generate_type_vars(
+    emitter: Emitter,
+    type_info: TypeInfo,
+) -> list[str]:
+    """Generate ``TypeVar`` declarations for a generic struct's parameters.
+
+    Returns the list of TypeVar names for use in the ``Generic[...]`` base.
+    """
+    node: dict = type_info.node
+    params = node.get("parameters", [])
+
+    tv_names: list[str] = []
+    for param in params:
+        tv_name = param["name"]
+        emitter.add_typing_import("TypeVar")
+        emitter.add_type_alias(tv_name, f'TypeVar("{tv_name}")')
+        tv_names.append(tv_name)
+
+    if tv_names:
+        emitter.add_blank_line()
+
+    return tv_names
+
+
+def resolve_brand(
+    brand_dict: dict,
+    registry: TypeRegistry,
+) -> list[str] | None:
+    """Resolve brand bindings to Python type strings.
+
+    Given a brand dict like::
+
+        {"scopes": [{"bind": [{"type": {"text": null}}], "scopeId": ...}]}
+
+    Returns the resolved Python types, e.g. ``["str"]``.
+
+    Returns ``None`` if the brand cannot be resolved.
+    """
+    from .type_resolver import resolve_type
+
+    scopes = brand_dict.get("scopes", [])
+    bindings: list[str] = []
+
+    for scope in scopes:
+        if "bind" in scope:
+            for binding in scope["bind"]:
+                type_dict = binding.get("type", {})
+                py_type = resolve_type(type_dict, registry)
+                if py_type is not None:
+                    bindings.append(py_type.render())
+                else:
+                    bindings.append("Any")
+        elif "inherit" in scope:
+            # inherit means "use the parent's parameter binding"
+            bindings.append("Any")  # Simplified for now
+
+    return bindings if bindings else None

src/capnp_stubgen/gen_struct.py

@@ -12,7 +12,9 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING
 
+from .gen_const import generate_const
 from .gen_enum import generate_enum
+from .gen_generic import generate_type_vars
 from .type_resolver import resolve_type
 from .utils import type_id_to_int
 
@@ -68,7 +70,16 @@ def generate_struct(
                     non_union_fields.append((field_name, type_str))
 
     # ── class: main type ───────────────────────────────────────────────
-    emitter.begin_class(name)
+    # Generic type: generate TypeVars and Generic[T] base
+    tv_names: list[str] = []
+    if type_info.generic_params:
+        tv_names = generate_type_vars(emitter, type_info)
+        emitter.add_typing_import("Generic")
+
+    if tv_names:
+        emitter.begin_class(name, bases=[f"Generic[{', '.join(tv_names)}]"])
+    else:
+        emitter.begin_class(name)
 
     for field_name, type_str in non_union_fields:
         emitter.add_field(field_name, type_str)
@@ -82,6 +93,12 @@ def generate_struct(
             emitter.add_blank_line()
             generate_enum(emitter, nt)
 
+    # Nested constants (class-level)
+    for nt in nested_types:
+        if nt.kind == "const":
+            emitter.add_blank_line()
+            generate_const(emitter, nt, registry)
+
     # Factory methods + to_dict
     _generate_factory_methods(emitter, name)
     emitter.add_method("to_dict", params=["self"], return_type="dict")
@@ -127,10 +144,10 @@ def _resolve_field_type(
     which = _type_which(type_dict)
 
     if which == "struct":
-        type_id = type_id_to_int(type_dict["struct"]["typeId"])
-        info = registry.get(type_id)
-        if info is not None:
-            q = info.scoped_name
+        # Use resolve_type to handle brand bindings
+        py_type = resolve_type(type_dict, registry)
+        if py_type is not None:
+            q = py_type.render()
             return f"{q} | {q}Builder | {q}Reader"
         return "Any"
 

src/capnp_stubgen/plugin.py

@@ -16,6 +16,7 @@ import sys
 from typing import TYPE_CHECKING
 
 from .emitter import Emitter
+from .gen_const import generate_const
 from .gen_enum import generate_enum
 from .gen_struct import generate_struct
 from .models import TypeRegistry
@@ -119,5 +120,7 @@ def _generate_file(
             generate_enum(emitter, type_info)
         elif type_info.kind == "struct":
             generate_struct(emitter, type_info, registry)
+        elif type_info.kind == "const":
+            generate_const(emitter, type_info, registry)
 
     return emitter.render()

src/capnp_stubgen/type_resolver.py

@@ -63,7 +63,14 @@ def resolve_type(
     # ── struct ─────────────────────────────────────────────────────────
     if which == "struct":
         type_id = type_id_to_int(type_dict["struct"]["typeId"])
-        return _resolve_named_type(type_id, registry)
+        base_type = _resolve_named_type(type_id, registry)
+        brand = type_dict["struct"].get("brand", {})
+        if brand:
+            from .gen_generic import resolve_brand
+            bindings = resolve_brand(brand, registry)
+            if bindings:
+                base_type.params = [PythonType(name=b) for b in bindings]
+        return base_type
 
     # ── interface ──────────────────────────────────────────────────────
     if which == "interface":
@@ -72,7 +79,7 @@ def resolve_type(
 
     # ── anyPointer ─────────────────────────────────────────────────────
     if which == "anyPointer":
-        return _resolve_any_pointer(type_dict["anyPointer"])
+        return _resolve_any_pointer(type_dict["anyPointer"], registry)
 
     return PythonType(name="Any")
 
@@ -121,13 +128,20 @@ def _resolve_named_type(type_id: int, registry: TypeRegistry) -> PythonType:
     return PythonType(name=info.name)
 
 
-def _resolve_any_pointer(ap_dict: dict) -> PythonType | None:
+def _resolve_any_pointer(
+    ap_dict: dict, registry: TypeRegistry
+) -> PythonType | None:
     """Resolve an AnyPointer type."""
-    sub = _type_which(ap_dict)
-    if sub == "unconstrained":
+    if "unconstrained" in ap_dict:
         return PythonType(name="Any")
-    if sub == "parameter":
-        return PythonType(name="Any")  # Simplified for Phase 1
-    if sub == "implicitMethodParameter":
+    if "parameter" in ap_dict:
+        # Look up the generic parameter name from the parent scope
+        scope_id = type_id_to_int(ap_dict["parameter"]["scopeId"])
+        param_index = ap_dict["parameter"]["parameterIndex"]
+        info = registry.get(scope_id)
+        if info is not None and param_index < len(info.generic_params):
+            return PythonType(name=info.generic_params[param_index])
+        return PythonType(name="Any")
+    if "implicitMethodParameter" in ap_dict:
         return None
     return PythonType(name="Any")