Using generate_cstr(true) breaks output format

[gwenn]

To reproduce,

• checkout https://github.com/rusqlite/rusqlite
• in libsqlite3-sys folder, execute upgrade.sh script

Without the following patch, generated bindings are correctly formatted.
But not with:

diff --git a/libsqlite3-sys/build.rs b/libsqlite3-sys/build.rs
index f96d656..53778b7 100644
--- a/libsqlite3-sys/build.rs
+++ b/libsqlite3-sys/build.rs
@@ -533,6 +533,7 @@ mod bindings {
         let mut bindings = bindgen::builder()
             .default_macro_constant_type(bindgen::MacroTypeVariation::Signed)
             .disable_nested_struct_naming()
+           .generate_cstr(true)
             .trust_clang_mangling(false)
             .header(header.clone())
             .parse_callbacks(Box::new(SqliteTypeChooser));

[ojeda]

Could you please minimize / give an example of the difference? Thanks!

[nyurik]

This is due to rustfmt not understanding the c"..." syntax -- which is only available with the 2021+ edition. The issue is that bindgen executes rustfmt without the --edition param, so rustfmt defaults to 2015. I think we can just add the edition parameter, setting it to 2021 if we generate the C-literals

See also https://rust-lang.zulipchat.com/#narrow/channel/469104-wg-bindgen/topic/Rustfmt.20and.20editions

[nyurik]

A workaround for this issue: create a rustfmt.toml in the root of your project, and add edition = "2021" to it

[pvdrz]

A workaround for this issue: create a rustfmt.toml in the root of your project, and add edition = "2021" to it

indeed, if you use a feature only available on edition 2021, you have to use a toolchain with that edition enabled.

I wouldn't say this is a workaround.

[nyurik]

I think its a workaround because a user would expect this to work automagically - i.e. bindgen output should be proper in every environment - thus we really need to pass --edition param to rustfmt when needed. I may try to hack a patch for that

[pvdrz]

I think its a workaround because a user would expect this to work automagically - i.e. bindgen output should be proper in every environment

In that case maybe we should unconditionally use 2018 as the default edition instead.

thus we really need to pass --edition param to rustfmt when needed.

Yes but you can also pass the edition in your rustfmt.toml. I think this is basically the same issue as with the msrv. You have to set your edition everywhere (Cargo.toml, rustfmt.toml and bindgen) otherwise you'll have unexpected outputs.

[nyurik]

Is there ever a case when bindgen 2018 output can be formatted in some broken way by the 2021 edition formatter? If not, we might as well pass the --edition 2021 to the rustfmt if the MSRV is for the version that supports it. The rest of the user code can still be using 2018 or anything else based on Cargo.toml - bindgen doesn't care about that

[nyurik]

#3063 fixes this issue