Originally from symfony/symfony#52106 (comment) from @tacman

The above require now works, thanks!

When I try to install asset-mapper:^6.4 in an existing project that's been upgraded to 6.4-DEV, I'm getting an error:

bash
composer req symfony/asset-mapper:^6.4

Symfony operations: 1 recipe (f9876b0bb3302355035a27b85d2368f3)
  - Configuring symfony/asset-mapper (>=6.4): From github.com/symfony/recipes:main
Executing script importmap:require [OK]
Executing script importmap:require [KO]
 [KO]
Script importmap:require returned with error code 1
!!  
!!  In ControllersMapGenerator.php line 75:
!!                                                         
!!    Warning: Attempt to read property "content" on null  
!!                                                         
!!  
!!  importmap:require [--entrypoint] [--path PATH] [--] <packages>...
!!  
!!  

The lines in question are

        foreach ($finder as $file) {
            $name = $file->getRelativePathname();
            $name = str_replace(['_controller.js', '-controller.js'], '', $name);
            $name = str_replace(['_', '/'], ['-', '--'], $name);

            $asset = $this->assetMapper->getAssetFromSourcePath($file->getRealPath());
            $isLazy = preg_match('/\/\*\s*stimulusFetch:\s*\'lazy\'\s*\*\//i', $asset->content);

            $controllersMap[$name] = new MappedControllerAsset($asset, $isLazy);
        }

so I suspect this has something to do with this project originally being in 6.3 and now being updated. Might it be possible to get a better message? $asset is null, and so maybe check for that and throw and error that includes the file->getRealPath().

The component installs okay, it's failing during the recipe, but I'm not sure what the full command is that the recipe is trying to run.

Executing script importmap:require [OK]

It would be helpful if the arguments were in this debug line, so I could isolate the problem.