More plugins: splashscreen and importmap (#938)

This PR move codes from main.ts into two new plugins:

- splashscreen (formerly known as py-loader)
- importmap

The old setting config.autoclose_loader is still supported but deprecated; the new setting is config.splashscreen.autoclose.

Moreover, it does a small refactoring around UserError: now UserErrors are correctly caught even if they are raised from within afterRuntimeLoad.

pyscriptjs/src/exceptions.ts

@@ -1,9 +1,14 @@
 const CLOSEBUTTON = `<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill="currentColor" width="12px"><path d='M.293.293a1 1 0 011.414 0L8 6.586 14.293.293a1 1 0 111.414 1.414L9.414 8l6.293 6.293a1 1 0 01-1.414 1.414L8 9.414l-6.293 6.293a1 1 0 01-1.414-1.414L6.586 8 .293 1.707a1 1 0 010-1.414z'/></svg>`;
 
+type MessageType = "text" | "html";
+
 export class UserError extends Error {
-  constructor(message: string) {
-    super(message)
-    this.name = "UserError"
+  messageType: MessageType;
+
+  constructor(message: string, t: MessageType = "text") {
+    super(message);
+    this.name = "UserError";
+    this.messageType = t;
   }
 }
 
@@ -17,7 +22,7 @@ export class FetchError extends Error {
 export function _createAlertBanner(
   message: string,
   level: "error" | "warning" = "error",
-  messageType: "text" | "html" = "text",
+  messageType: MessageType = "text",
   logMessage = true) {
   // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
   switch (`log-${level}-${logMessage}`) {
@@ -53,27 +58,3 @@ export function _createAlertBanner(
 
   document.body.prepend(banner);
 }
-
-/*
-* This function is used to handle UserError, if we see an error of this
-* type, we will automatically create a banner on the page that will tell
-* the user what went wrong. Note that the error will still stop execution,
-* any other errors we will simply throw them and no banner will be shown.
-*/
-export function withUserErrorHandler(fn) {
-  try {
-    return fn();
-  } catch (error: unknown) {
-    if (error instanceof UserError) {
-      /*
-      *  Display a page-wide error message to show that something has gone wrong with
-      *  PyScript or Pyodide during loading. Probably not be used for issues that occur within
-      *  Python scripts, since stderr can be routed to somewhere in the DOM
-      */
-      _createAlertBanner(error.message);
-    }
-    else {
-      throw error;
-    }
-  }
-}