How would one achieve conditional compilation with Rust projects that have doctests?

问题

I've used conditional compilation to change the type signature of a function, and now the same doctest can't be run for both "feature" modes, so I need a way to opt-out of the doctests.

I've tried merging #[cfg_attr(feature = "rss_loose", ignore)] used in normal tests and ///rust,ignore to make ///rust,cfg_attr(feature = "rss_loose", ignore) but this doesn't seem to work.

回答1:

Just write two different sets of documentation and tests and it will all work as-is:

/// ```
/// assert_eq!(42, dt::foo());
/// ```
#[cfg(not(feature = "alternate"))]
pub fn foo() -> u8 { 42 }

/// ```
/// assert_eq!(true, dt::foo());
/// ```
#[cfg(feature = "alternate")]
pub fn foo() -> bool { true }

$ cargo test
   Compiling dt v0.1.0 (file:///private/tmp/dt)
     Running target/debug/dt-c3e297f8592542b5

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests dt

running 1 test
test foo_0 ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

$ cargo test --features=alternate
   Compiling dt v0.1.0 (file:///private/tmp/dt)
     Running target/debug/dt-c3e297f8592542b5

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured

   Doc-tests dt

running 1 test
test foo_0 ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured

来源：https://stackoverflow.com/questions/38292741/how-would-one-achieve-conditional-compilation-with-rust-projects-that-have-docte