A build dependency can force runtime features to be enabled in the final artifact

[mwcampbell]

Minimal repro test case

In Cargo.toml, default_features is set to false for env_logger. But when you build the binary, env_logger has all features enabled anyway, as is evident from the binary size and the output of cargo-tree.

This is caused by the dependency on speech-dispatcher, which has an indirect build dependency on bindgen, which depends on env_logger with default features. This dependency forces env_logger in the final program to have default features even when built on a non-Linux platform (the dependency on speech-dispatcher is conditional). If you remove the dependency on speech-dispatcher, then the optional features of env_logger are disabled as expected.

Tested with Cargo 1.45.1 (f242df6 2020-07-22).

[ehuss]

This should already be implemented with the -Zfeatures option (see docs and #7915).

[mwcampbell]

Ah, sorry for the duplicate.