teor The problem is, it won't fail. It will compile just fine but produce no executables. Which brings us back to needing a parser/resolver, which can parse the cargo metadata and look if a feature flag produced any executables. Temporarily, I will try building with default first, check if at least 1 executable was produced, else build with all features: https://github.com/pkgforge-cargo/builder/commit/06bbb506e123ae7d2a1d9fdd8d459131a596b350

We use the --all-features flag because some crates don't produce an executable unless we specifically use the --feature flag. We couldn't find an easy way to determine what features produced an executable, so decided to use --all-features directly. What you hypothesize is actually true. We notice some errors were due to us using this --all-features flag. In a future update, I will write a resolver which will resolve and use the correct feature flag automatically. But that's far in the future.