Fix lifetime for pyExec results (#1540)

Currently if the result from pyExec is a PyProxy, it gets destroyed.
This switches to using `to_js` to handle this (it is better to use
than an explicit `create_proxy` since it automatically decides whether
to create a proxy or not).

I also added `destroyIfProxy` which checks if something is a `PyProxy`
and then destroys it. Each use of `pyExec` needs to call `destroyIfProxy`
on the result after it is done with it.

pyscriptjs/src/components/pyrepl.ts

@@ -191,7 +191,7 @@ export function make_PyRepl(interpreter: InterpreterClient, app: PyScriptApp) {
                 pyReplTag: this,
                 result,
             });
-
+            await interpreter._remote.destroyIfProxy(result);
             this.autogenerateMaybe();
         }
 

pyscriptjs/src/components/pyscript.ts

@@ -36,6 +36,7 @@ export function make_PyScript(interpreter: InterpreterClient, app: PyScriptApp)
             await app.plugins.beforePyScriptExec({ interpreter, src, pyScriptTag });
             const { result } = await pyExec(interpreter, src, pyScriptTag);
             await app.plugins.afterPyScriptExec({ interpreter, src, pyScriptTag, result });
+            await interpreter._remote.destroyIfProxy(result);
         } finally {
             releaseLock();
             app.decrementPendingTags();

pyscriptjs/src/python/pyscript/_internal.py

@@ -4,7 +4,7 @@ from contextlib import contextmanager
 
 from js import Object
 from pyodide.code import eval_code
-from pyodide.ffi import JsProxy
+from pyodide.ffi import JsProxy, to_js
 
 from ._event_loop import (
     defer_user_asyncio,
@@ -103,7 +103,7 @@ def run_pyscript(code: str, id: str = None) -> JsProxy:
     with display_target(id), defer_user_asyncio():
         result = eval_code(code, globals=__main__.__dict__)
 
-    return Object.new(result=result)
+    return to_js({"result": result}, depth=1, dict_converter=Object.fromEntries)
 
 
 __all__ = [

pyscriptjs/src/remote_interpreter.ts

@@ -274,6 +274,20 @@ export class RemoteInterpreter extends Object {
         this.FS.writeFile(path, data, { canOwn: true });
     }
 
+    destroyIfProxy(px: any): void {
+        if (this.interface.ffi) {
+            // Pyodide 0.23
+            if (px instanceof this.interface.ffi.PyProxy) {
+                px.destroy();
+            }
+        } else {
+            // older Pyodide
+            if (this.interface.isPyProxy(px)) {
+                px.destroy();
+            }
+        }
+    }
+
     /**
      * delegates clearing importlib's module path
      * caches to the underlying interface

pyscriptjs/tests/integration/test_py_repl.py

@@ -674,3 +674,47 @@ class TestPyRepl(PyScriptTest):
             "Are your filename and path correct?"
         )
         assert self.console.error.lines[-1] == errorMsg
+
+    @skip_worker("dont-care")
+    def test_repl_results(self):
+        self.writefile("loadReplSrc2.py", "2")
+        self.writefile("loadReplSrc3.py", "print('3')")
+
+        self.pyscript_run(
+            """
+            <py-repl id="py-repl1" output="out1">
+            42
+            </py-repl>
+            <div id="out1"></div>
+
+            <py-repl id="py-repl2" output="out2">
+            c = [1,2,3]
+            from sys import getrefcount
+            # should print 2: 1 from the reference c and 1 since getrefcount
+            # holds a reference to its argument
+            print(getrefcount(c))
+            c
+            </py-repl>
+            <div id="out2"></div>
+
+            <py-repl id="py-repl3" output="out3">
+            # should also print 2: if it prints 3 that would mean that c was not properly
+            # released by py-repl
+            getrefcount(c)
+            </py-repl>
+            <div id="out3"></div>
+            """
+        )
+        py_repl1 = self.page.locator("py-repl#py-repl1")
+        py_repl1.locator("button").click()
+
+        py_repl2 = self.page.locator("py-repl#py-repl2")
+        py_repl2.locator("button").click()
+
+        py_repl3 = self.page.locator("py-repl#py-repl3")
+        py_repl3.locator("button").click()
+
+        assert self.page.wait_for_selector("#out1").inner_text() == "42"
+        assert self.page.wait_for_selector("#out2").inner_text() == "2\n\n[1, 2, 3]"
+        # Check that c was released
+        assert self.page.wait_for_selector("#out3").inner_text() == "2"