Feature: Add support for __getattr__ (#234)

Author: robert3005

docs/guide/classes.md

@@ -173,17 +173,18 @@ const inquiry = fn(*Self) !bool;
 
 ### Type Methods
 
-| Method     | Signature                                |
-| :--------- | :--------------------------------------- |
-| `__init__` | `#!zig fn() void`                        |
-| `__init__` | `#!zig fn(*Self) !void`                  |
-| `__init__` | `#!zig fn(*Self, CallArgs) !void`        |
-| `__del__`  | `#!zig fn(*Self) void`                   |
-| `__repr__` | `#!zig fn(*Self) !py.PyString`           |
-| `__str__`  | `#!zig fn(*Self) !py.PyString`           |
-| `__call__` | `#!zig fn(*Self, CallArgs) !py.PyObject` |
-| `__iter__` | `#!zig fn(*Self) !object`                |
-| `__next__` | `#!zig fn(*Self) !?object`               |
+| Method        | Signature                                |
+| :------------ | :--------------------------------------- |
+| `__init__`    | `#!zig fn() void`                        |
+| `__init__`    | `#!zig fn(*Self) !void`                  |
+| `__init__`    | `#!zig fn(*Self, CallArgs) !void`        |
+| `__del__`     | `#!zig fn(*Self) void`                   |
+| `__repr__`    | `#!zig fn(*Self) !py.PyString`           |
+| `__str__`     | `#!zig fn(*Self) !py.PyString`           |
+| `__call__`    | `#!zig fn(*Self, CallArgs) !py.PyObject` |
+| `__iter__`    | `#!zig fn(*Self) !object`                |
+| `__next__`    | `#!zig fn(*Self) !?object`               |
+| `__getattr__` | `#!zig fn(*Self, object) !?object`       |
 
 ### Sequence Methods
 

example/classes.pyi

@@ -23,6 +23,15 @@ class Counter:
 
     count: ...
 
+class GetAttr:
+    def __init__(self, /):
+        pass
+    def __getattribute__(self, name, /):
+        """
+        Return getattr(self, name).
+        """
+        ...
+
 class Hash:
     def __init__(self, x, /):
         pass

example/classes.zig

@@ -172,6 +172,22 @@ pub const Callable = py.class(struct {
     }
 });
 
+pub const GetAttr = py.class(struct {
+    const Self = @This();
+
+    pub fn __init__(self: *Self) void {
+        _ = self;
+    }
+
+    pub fn __getattr__(self: *const Self, attr: py.PyString) !py.PyObject {
+        const name = try attr.asSlice();
+        if (std.mem.eql(u8, name, "number")) {
+            return py.create(42);
+        }
+        return py.object(self).getAttribute(name);
+    }
+});
+
 comptime {
     py.rootmodule(@This());
 }

pydust/src/functions.zig

@@ -81,6 +81,7 @@ pub const BinaryOperators = std.ComptimeStringMap(c_int, .{
     .{ "__matmul__", ffi.Py_nb_matrix_multiply },
     .{ "__imatmul__", ffi.Py_nb_inplace_matrix_multiply },
     .{ "__getitem__", ffi.Py_mp_subscript },
+    .{ "__getattr__", ffi.Py_tp_getattro },
 });
 
 // TODO(marko): Move this somewhere.

pydust/src/types/obj.zig

@@ -55,6 +55,14 @@ pub const PyObject = extern struct {
         return .{ .py = ffi.PyObject_GetAttr(self.py, attrStr.obj.py) orelse return PyError.PyRaised };
     }
 
+    /// Returns a new reference to the attribute of the object using default lookup semantics.
+    pub fn getAttribute(self: PyObject, attrName: []const u8) !py.PyObject {
+        const attrStr = try py.PyString.create(attrName);
+        defer attrStr.decref();
+
+        return .{ .py = ffi.PyObject_GenericGetAttr(self.py, attrStr.obj.py) orelse return PyError.PyRaised };
+    }
+
     /// Returns a new reference to the attribute of the object.
     pub fn getAs(self: PyObject, comptime T: type, attrName: []const u8) !T {
         return try py.as(T, try self.get(attrName));

test/test_classes.py

@@ -98,3 +98,11 @@ def test_refcnt():
     rc = sys.getrefcount(classes)
     classes.Hash(42)
     assert sys.getrefcount(classes) == rc
+
+
+def test_getattr():
+    c = classes.GetAttr()
+    assert c.number == 42
+    with pytest.raises(AttributeError) as exc_info:
+        c.attr
+    assert str(exc_info.value) == "'example.classes.GetAttr' object has no attribute 'attr'"