Move pyodide to a web worker (#1333)

This PR adds support for optionally running pyodide in a web worker:

- add a new option config.execution_thread, which can be `main` or `worker`. The default is `main`

- improve the test machinery so that we run all tests twice, once for `main` and once for `worker`

- add a new esbuild target which builds the code for the worker

The support for workers is not complete and many features are still missing: there are 71 tests which are marked as `@skip_worker`, but we can fix them in subsequent PRs.

The vast majority of tests fail because js.document is unavailable: for it to run transparently, we need the "auto-syncify" feature of synclink.


Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>
Co-authored-by: Madhur Tandon <20173739+madhur-tandon@users.noreply.github.com>

pyscriptjs/tests/integration/test_01_basic.py

@@ -2,11 +2,37 @@ import re
 
 import pytest
 
-from .support import JsErrors, PyScriptTest
+from .support import JsErrors, PyScriptTest, skip_worker
 
 
 class TestBasic(PyScriptTest):
     def test_pyscript_hello(self):
+        self.pyscript_run(
+            """
+            <py-script>
+                import js
+                js.console.log('hello pyscript')
+            </py-script>
+            """
+        )
+        assert self.console.log.lines == ["hello pyscript"]
+
+    def test_execution_thread(self):
+        self.pyscript_run(
+            """
+            <!-- we don't really need anything here, we just want to check that
+                 pyscript starts -->
+            """
+        )
+        assert self.execution_thread in ("main", "worker")
+        if self.execution_thread == "main":
+            where = "the main thread"
+        elif self.execution_thread == "worker":
+            where = "a web worker"
+        expected = f"[pyscript/main] Starting the interpreter in {where}"
+        assert expected in self.console.info.lines
+
+    def test_print(self):
         self.pyscript_run(
             """
             <py-script>
@@ -53,6 +79,9 @@ class TestBasic(PyScriptTest):
         )
 
         self.page.locator("button").click()
+        self.wait_for_console(
+            "Exception: this is an error inside handler", match_substring=True
+        )
 
         ## error in console
         tb_lines = self.console.error.lines[-1].splitlines()
@@ -120,6 +149,7 @@ class TestBasic(PyScriptTest):
             "hello asciitree",  # printed by us
         ]
 
+    @skip_worker("FIXME: the banner doesn't appear")
     def test_non_existent_package(self):
         self.pyscript_run(
             """
@@ -139,6 +169,7 @@ class TestBasic(PyScriptTest):
         alert_banner = self.page.wait_for_selector(".alert-banner")
         assert expected_alert_banner_msg in alert_banner.inner_text()
 
+    @skip_worker("FIXME: the banner doesn't appear")
     def test_no_python_wheel(self):
         self.pyscript_run(
             """
@@ -240,6 +271,7 @@ class TestBasic(PyScriptTest):
             is not None
         )
 
+    @skip_worker("FIXME: showWarning()")
     def test_assert_no_banners(self):
         """
         Test that the DOM doesn't contain error/warning banners