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Add a compile_error!() when central crate features clash #110

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Add a compile_error!() when central crate features clash #110

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06ed053
fix(features): compile_error! on clashing features
onkoe Sep 5, 2024
5115eef
fix(v4l2/api): put user-facing features in #[cfg]s
onkoe Sep 5, 2024
7d29fb9
docs: update `README.md` to contain feature info
onkoe Sep 5, 2024
ab47652
fix(v4l2/api): correct the feature order
onkoe Sep 5, 2024
adbc618
docs(README): add missing backticks
onkoe Sep 5, 2024
cd40d4f
docs(lib): expand on r-a workaround
onkoe Sep 5, 2024
f110a2e
docs(README): specify v4l2 for kernel headers
onkoe Sep 5, 2024
b650660
chore: wrap the compile_error()!
onkoe Sep 5, 2024
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11 changes: 9 additions & 2 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,12 +67,19 @@
//!
//! Have a look at the examples to learn more about device and buffer management.

#[cfg(feature = "v4l-sys")]
#[cfg(all(feature = "libv4l", feature = "v4l2"))]
compile_error!("You may not enable both `v4l-sys` and `v4l2-sys` features at the same time. Try disabling one of them. If you only specified one feature, you may wish to add `default-features = false` as a dependency key.");

#[cfg(all(feature = "libv4l", not(feature = "v4l2")))]
pub use v4l_sys;

#[cfg(feature = "v4l2-sys")]
#[cfg(all(feature = "v4l2", not(feature = "libv4l")))]
pub use v4l2_sys as v4l_sys;

// calms down rust-analyzer when `rust-analyzer.cargo.features = "all"`
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#[cfg(all(feature = "v4l2", feature = "libv4l"))]
pub use v4l_sys;
Comment on lines +86 to +87
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Why not do what you've done in the second patch (but the other way around):

  1. Remove these two lines;
  2. Change the above to: 
    -#[cfg(all(feature = "libv4l", not(feature = "v4l2")))]
+#[cfg(feature = "v4l2")]
 pub use v4l2_sys as v4l_sys;

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I would also prefer this, but I found that doing so breaks one of the features.

On the other hand, it doesn't occur in api.rs since we're not already re-exporting one of its modules. If you find a way to do it, though, please let me know!

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It would match the choice in api.rs to prefer v4l2 code in the case that both features are contemporarily enabled, but it is less of an issue now that the comment has been removed.

Either way, this seems better to me:

diff --git a/src/lib.rs b/src/lib.rs
index 2272aeb..1237262 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -74,16 +74,12 @@ compile_error!(
     add `default-features = false` as a dependency key."
 );

-#[cfg(all(feature = "libv4l", not(feature = "v4l2")))]
-pub use v4l_sys;
-
-#[cfg(all(feature = "v4l2", not(feature = "libv4l")))]
-pub use v4l2_sys as v4l_sys;
-
-// calms down rust-analyzer when `rust-analyzer.cargo.features = "all"`,
-// though the `compile_error!()` above prevents this from being a valid,
+// calm down rust-analyzer when `rust-analyzer.cargo.features = "all"` by having only one `v4l_sys`
+// crate in scope, even though the `compile_error!()` above prevents this from being a valid,
 // compilable configuration.
-#[cfg(all(feature = "v4l2", feature = "libv4l"))]
+#[cfg(feature = "v4l2")]
+pub use v4l2_sys as v4l_sys;
+#[cfg(all(feature = "libv4l", not(feature = "v4l2")))]
 pub use v4l_sys;

 pub mod v4l2;


pub mod v4l2;

pub mod buffer;
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