[next] Include most basic error plugin (#1677)

pyscript.core/src/core.js

@@ -5,6 +5,7 @@ import { htmlDecode } from "./utils.js";
 import sync from "./sync.js";
 
 import stdlib from "./stdlib.js";
+import plugins from "./plugins.js";
 
 // TODO: this is not strictly polyscript related but handy ... not sure
 //       we should factor this utility out a part but this works anyway.
@@ -13,7 +14,7 @@ import { Hook } from "../node_modules/polyscript/esm/worker/hooks.js";
 
 import { robustFetch as fetch } from "./fetch.js";
 
-const { assign, defineProperty } = Object;
+const { assign, defineProperty, entries } = Object;
 
 const getText = (body) => body.text();
 
@@ -163,6 +164,16 @@ define("py", {
             shouldRegister = false;
             registerModule(pyodide);
         }
+
+        // load plugins unless specified otherwise
+        const toBeAwaited = [];
+        for (const [key, value] of entries(plugins)) {
+            if (!pyodide.config?.plugins?.includes(`!${key}`))
+                toBeAwaited.push(value());
+        }
+
+        if (toBeAwaited.length) await Promise.all(toBeAwaited);
+
         // allows plugins to do whatever they want with the element
         // before regular stuff happens in here
         for (const callback of hooks.onInterpreterReady)

pyscript.core/src/plugins.js

@@ -0,0 +1,4 @@
+// ⚠️ This file is an artifact: DO NOT MODIFY
+export default {
+    error: () => import("./plugins/error.js"),
+};

pyscript.core/src/plugins/error.js

@@ -0,0 +1,40 @@
+// PyScript Error Plugin
+import { hooks } from "../core.js";
+
+hooks.onBeforeRun.add(function override(pyScript) {
+    // be sure this override happens only once
+    hooks.onBeforeRun.delete(override);
+
+    // trap generic `stderr` to propagate to it regardless
+    const { stderr } = pyScript.io;
+
+    // override it with our own logic
+    pyScript.io.stderr = (...args) => {
+        // grab the message of the first argument (Error)
+        const [{ message }] = args;
+        // show it
+        notify(message);
+        // still let other plugins or PyScript itself do the rest
+        return stderr(...args);
+    };
+});
+
+// Error hook utilities
+
+// Custom function to show notifications
+function notify(message) {
+    const div = document.createElement("div");
+    div.className = "py-error";
+    div.textContent = message;
+    div.style.cssText = `
+    border: 1px solid red;
+    background: #ffdddd;
+    color: black;
+    font-family: courier, monospace;
+    white-space: pre;
+    overflow-x: auto;
+    padding: 8px;
+    margin-top: 8px;
+  `;
+    document.body.append(div);
+}