We are experiencing an issue with a Composer feed configured as a proxy for Packagist. While running composer install, our local Composer clients receive a 404 Not Found error specifically when attempting to download the .zip distribution of the package voku/simple_html_dom (version 4.8.10).

Steps to Reproduce:

• Configure a ProGet feed (composer-public-unvetted) as a Composer proxy to Packagist.

• list itemRun composer require voku/simple_html_dom:4.8.10 or include it in composer.json and run composer install.

• The Composer client successfully retrieves the package metadata (JSON) from list itemProGet.

• The client then attempts to download the artifact .zip file.

• The download fails with an HTTP 404 error returned by ProGet.

Diagnosis & Server Logs:
Upon inspecting the ProGet server logs, it appears that ProGet successfully downloads the package from the upstream source but fails to cache it locally. The internal parser throws an InvalidPackageException because it cannot locate the "name" property inside the package's manifest (composer.json). Because the caching process fails, ProGet returns a 404 to the requesting client.

Here is the exact stack trace from the ProGet diagnostic logs:

pg-1  |       Request starting HTTP/1.1 GET http://get.dev.com/composer/composer-public-unvetted/download/voku/simple_html_dom/4.8.10.zip - - -
pg-1  | An error occurred while attempting to cache pkg:composer/voku/simple_html_dom@4.8.10:File is not a valid manifest file.
pg-1  | Inedo.ProGet.InvalidPackageException: File is not a valid manifest file.
pg-1  |  ---> Inedo.ProGet.InvalidPackageException: Missing required property: name
pg-1  |    at Inedo.ProGet.Feeds.Composer.ComposerManifest..ctor(JsonElement root, String version, Boolean cloneElement) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E654949\Src\src\ProGet\Feeds\Composer\ComposerManifest.cs:line 44
pg-1  |    at Inedo.ProGet.Feeds.Composer.ComposerManifest.Inedo.ProGet.Feeds.IPackageManifest<Inedo.ProGet.Feeds.Composer.ComposerManifest>.ReadAndParseMetadataFromPackage(Stream packageStream, PackageInstallContext context) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E654949\Src\src\ProGet\Feeds\Composer\ComposerManifest.cs:line 237
pg-1  |    --- End of inner exception stack trace ---
pg-1  |    at Inedo.ProGet.Feeds.Composer.ComposerManifest.Inedo.ProGet.Feeds.IPackageManifest<Inedo.ProGet.Feeds.Composer.ComposerManifest>.ReadAndParseMetadataFromPackage(Stream packageStream, PackageInstallContext context) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E654949\Src\src\ProGet\Feeds\Composer\ComposerManifest.cs:line 242
pg-1  |    at Inedo.ProGet.Feeds.PackageFeed`5.AddPackageAsync(Stream stream, InstallPackageOptions options, PackageInstallContext context, Nullable`1 publishDate, Boolean listed, CancellationToken cancellationToken) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E654949\Src\src\ProGet\Feeds\PackageFeed.PackageAdd.cs:line 67
pg-1  |    at Inedo.ProGet.Feeds.PackageFeed`5.AddPackageAsync(Stream stream, InstallPackageOptions options, PackageInstallContext context, Nullable`1 publishDate, Boolean listed, CancellationToken cancellationToken) in C:\Users\builds\AppData\Local\Temp\InedoAgent\BuildMaster\192.168.44.60\Temp\_E654949\Src\src\ProGet\Feeds\PackageFeed.PackageAdd.cs:line 152
pg-1  |    at Inedo.ProGet.Feeds.PackageFeed`5.DownloadPackageAsync(TPackage package, IPackageDownloadContext context, OpenPackageOptions options, PackageInstallContext installContext, CancellationToken cancellationToken)
pg-1  | A 404 error occurred in composer-public-unvetted: Package simple_html_dom 4.8.10 not found.
pg-1  | An error occurred processing a GET request to http://get.dev.com/composer/composer-public-unvetted/download/voku/simple_html_dom/4.8.10.zip: Package simple_html_dom 4.8.10 not found.
pg-1  | info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
pg-1  |       Request finished HTTP/1.1 GET http://get.dev.com/composer/composer-public-unvetted/download/voku/simple_html_dom/4.8.10.zip - 404 1230 application/json 127.5770ms

Expected Behavior:

ProGet should accurately extract the composer.json from the upstream artifact, bypass strict validation if upstream parsing differs, or gracefully handle the artifact caching so the Composer client can successfully download the .zip file. The package is completely valid and installs normally when downloading directly from Packagist.

Could you please investigate why the ComposerManifest parser is failing on this specific package and provide a solution or workaround to prevent it from failing the entire cache operation?

Thank you!