Proposal to split afl.rs into two packages

[smoelius]

I propose that afl.rs be split into two package, cargo-afl and afl.

Moreover:

• Users install cargo-afl via cargo install cargo-afl, instead of cargo install afl like now.
• A compile error is generated when a user runs cargo install afl (similar to what cargo install rg does).
• A warning is generated when a user runs cargo build instead of cargo afl build on a crate that depends on afl.

The last bullet would be accomplished by a build script. Note that there is no easy way to accomplish this with the current one-package setup, because there is no easy way to tell why a build script is run (see rust-lang/cargo#4001).

Pros for these changes:

• The aforementioned warning will help avoid confusion (e.g., "error: linking with cc failed: exit code: 1" when "cargo build" #179).
• Building targets that rely on afl should be faster, because:
  • The current build script (which is intended for cargo-afl) will not need to be run.
  • cargo-afl's dependencies (e.g. clap) will not need to be built.

Cons:

• Maintaining a multi-package project is more difficult.
• User accustomed to running cargo install afl will have to adjust.
• CI that runs cargo install afl will break. (It may be possible to have a transition period where we generate a warning.)

Does anyone have strong opinions on this? If so, could you please voice them?

[louismerlin]

That sounds like a great idea!

Another way to achieve cargo-afl's dependencies (e.g. clap) will not need to be built. is through features, like we do here.

The only difference in workflow this would create is that the afl package would have to be imported like this:

afl = { version = "*", default-features = false }

[smoelius]

Another way to achieve cargo-afl's dependencies (e.g. clap) will not need to be built. is through features, like we do here.

That's a very good point, @louismerlin. Thank you for raising it.

[smoelius]

I've received two positive responses (one here and one offline) and no negative responses.

So in about a week, I'm going to implement a transitional message to let users know this change is coming.

[smoelius]

Completed by #375