I'm not familiar with this code myself, so bear with me.

Here's a passing test for FileCache::import(): https://github.com/lipemat/wp-cli/commit/1b484041a8b1b5759b15f917713a7b10a5bdd56a

$key is a cache key, which I think looks typically like plugin/my-fixture-plugin-1.0.0.zip but there is code in FileCache::validate_key() which handles full URLs too.

I suspect your sample data looks something like http://premiumplugins.com/download-latest/?auth=123 but may have been altered by WP CLI before being used as $key, I'm not sure.

$source is the filename of the temp file that has been downloaded by the http request and is probably typically a .zip file.

It's possible for a server to serve plugin.zip from http://premiumplugins.com/download-latest so it may or may not have the correct extension.

So what should a failing test look like with the current code?

Would you please add WP_CLI::error( "FileCache::import( '{$key}', '{$source}' )" ); to the beginning of the FileCache::import(), run it once with an offending premium plugin, and let me know what it prints (then remove it, naturally!).

I think your solution of "never worry about caching files whose type is ambiguous" is fine, but I'd like to write an accurate test for it.

"Warning: copy(-.): Failed to open stream: Permission denied".

I haven't been able to reproduce this. Is that the exact message? It may be better to test is_readable() on the $source file than check extensions, since unzip my-plugin-1.0.0 will work without the extension.

https://github.com/lipemat/wp-cli/commit/132222fb2ad998fb3a5b4a61c2f91caca5f26f9e

Here is the error you requested:

Error: FileCache::import( 'plugin/advanced-sidebar-menu-pro-9.5.7.', 'C:\Users\box\AppData\Local\Temp/664e5754330ad-TsJObX.tmp' )

Thanks. I'm on MacOS and that doesn't cause a failing test for me. But Microsoft says:

Do not end a file or directory name with a space or a period.

https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions

So when FileCache::validate_key() is passed a string ending in ., it is returning a filename ending in . which is invalid on Windows.

I think the fix is to use rtrim() in FileCache::validate_key(): c38a371

Will you manually test that please?

That seems to work with rtrim leaving a file in the cache without an extension.

Closing in favour of #5951. Thank you.