feat: add instanceMethod (#68)

Co-authored-by: Elias Sjögreen <elias@5monkeys.se>

Author: sigmaSd

src/python.ts

@@ -975,6 +975,34 @@ export class Python {
   callback(cb: PythonJSCallback): Callback {
     return new Callback(cb);
   }
+
+  /**
+   * Creates a Python instance method from a JavaScript callback.
+   *
+   * @description
+   * This method takes a JavaScript callback function and creates a Python instance method.
+   *
+   * The method returns both the created Python instance method and the Callback object.
+   * The Callback object is returned to allow the user to explicitly call its `destroy`
+   * method when it's no longer needed, ensuring proper resource management and
+   * freeing of memory.
+   *
+   * @example
+   * const [pyMethod, callback] = instanceMethod(myJSFunction);
+   * // Use pyMethod as needed
+   * // ...
+   * // When done, explicitly free the callback
+   * callback.destroy();
+   */
+  instanceMethod(cb: PythonJSCallback): [PyObject, Callback] {
+    const pythonCb = python.callback(cb);
+    const method = new PyObject(
+      py.PyInstanceMethod_New(
+        PyObject.from(pythonCb).handle,
+      ),
+    );
+    return [method, pythonCb];
+  }
 }
 
 /**

src/symbols.ts

@@ -249,4 +249,9 @@ export const SYMBOLS = {
     parameters: ["buffer", "pointer", "pointer"],
     result: "pointer",
   },
+
+  PyInstanceMethod_New: {
+    parameters: ["pointer"],
+    result: "pointer",
+  },
 } as const;

test/test.ts

@@ -325,6 +325,26 @@ Deno.test("exceptions", async (t) => {
   });
 });
 
+Deno.test("instance method", () => {
+  const { A } = python.runModule(
+    `
+class A:
+  def b(self):
+    return 4
+  `,
+    "cb_test.py",
+  );
+
+  const [m, cb] = python.instanceMethod((_args, self) => {
+    return self.b();
+  });
+  // Modifying PyObject modifes A
+  PyObject.from(A).setAttr("a", m);
+
+  assertEquals(new A().a.call().valueOf(), 4);
+  cb.destroy();
+});
+
 Deno.test("callbacks have signature", async (t) => {
   const inspect = python.import("inspect");