[TASK] Prepare import map prefix-based URL calculation

Import map resolution without a cache-bust suffix missed to join a
previously splitted path-string via slashes, when a prefix based
import-declaration was used to calculate the resulting URL of a
JavaScript bare module specifier (usecase: calculate the
URL of a bare module specifier for usage in a `<script src="">`
tag, where bare module specifiers like `@typo3/backend/foo.js` can
not be used directly as browsers will not map them by importmap).

Note: TYPO3 currently uses cache-bust suffixes only, as there
are no cache-bust prefixes yet. Therefore all prefix-paths are
recursively pre-calculated in `computeImportMaps()`, which effecively
skipped the broken codepath for the current environments, which means
this is a preparatory TASK and not a BUGFIX for the case when
once prefix-based cache-busting is added in #98481.

Resolves: #103954
Related: #98481
Releases: main, 13.4
Change-Id: Ia6046a5b9a18016cd8166bd8ec30738663c73a46
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84447
Reviewed-by: Benjamin Kott <benjamin.kott@outlook.com>
Reviewed-by: Andreas Kienast <akienast@scripting-base.de>
Tested-by: Benjamin Kott <benjamin.kott@outlook.com>
Tested-by: Andreas Kienast <akienast@scripting-base.de>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benjamin Franzke <ben@bnf.dev>

Author: bnf

typo3/sysext/core/Classes/Page/ImportMap.php

@@ -106,7 +106,7 @@ public function resolveImport(
                     if ($loadImportConfiguration) {
                         $this->loadDependency($package);
                     }
-                    return $imports[$prefix] . implode(array_slice($specifierParts, $i));
+                    return $imports[$prefix] . implode('/', array_slice($specifierParts, $i));
                 }
             }
         }

typo3/sysext/core/Tests/Unit/Page/Fixtures/ImportMap/core/Resources/Public/JavaScript/nested/module.js

@@ -101,6 +101,27 @@ public function resolveImport(): void
         self::assertStringStartsWith('Fixtures/ImportMap/core/Resources/Public/JavaScript/Contrib/lit/index.js?bust=', $url);
     }
 
+    #[Test]
+    public function resolveNestedUrlImportWithBustSuffix(): void
+    {
+        $this->packages = ['core'];
+        $importMap = new ImportMap($this->hashService, $this->getPackages());
+        $nestedUrl = $importMap->resolveImport('@typo3/core/nested/module.js');
+
+        self::assertStringStartsWith('Fixtures/ImportMap/core/Resources/Public/JavaScript/nested/module.js?bust=', $nestedUrl);
+    }
+
+    #[Test]
+    public function resolveNestedUrlImportWithoutBustSuffix(): void
+    {
+        $this->packages = ['core'];
+
+        $importMap = new ImportMap($this->hashService, $this->getPackages(), null, '', null, false);
+        $nestedUrl = $importMap->resolveImport('@typo3/core/nested/module.js');
+
+        self::assertEquals('Fixtures/ImportMap/core/Resources/Public/JavaScript/nested/module.js', $nestedUrl);
+    }
+
     #[Test]
     public function resolveAndImplicitlyIncludeModuleConfiguration(): void
     {