hot: improve import map validating

hot.ts

@@ -294,27 +294,43 @@ function parseImportMap() {
  return importMap;
  }
  const script = doc.querySelector("script[type=importmap]");
- let json = null;
  if (script) {
  try {
- json = parse(script.textContent!);
+ const json = parse(script.textContent!);
+ if (isObject(json)) {
+ const { imports, scopes } = json;
+ if (isObject(imports)) {
+ validateImports(imports);
+ importMap.imports = imports;
+ }
+ if (isObject(scopes)) {
+ validateScopes(scopes);
+ importMap.scopes = scopes;
+ }
+ }
  } catch (err) {
  console.error("Invalid importmap", err[kMessage]);
  }
  }
- if (isObject(json)) {
- const { imports, scopes } = json;
- for (const k in imports) {
- const url = imports[k];
- if (url) {
- importMap.imports[k] = url;
- }
+ return importMap;
+}
+
+function validateScopes(imports: Record<string, unknown>) {
+ for (const [k, v] of Object.entries(imports)) {
+ if (isObject(v)) {
+ validateImports(v);
+ } else {
+ delete imports[k];
  }
- if (isObject(scopes)) {
- importMap.scopes = scopes;
+ }
+}
+
+function validateImports(imports: Record<string, unknown>) {
+ for (const [k, v] of Object.entries(imports)) {
+ if (!v || typeof v !== "string") {
+ delete imports[k];
  }
  }
- return importMap;
 }
 
 /** create a cache proxy object. */