Re: [RFC PATCH 01/11] rust: qemu_api: do not disable lints outside bindgen-generated code

[Junjie Mao]

Paolo Bonzini <pbonzini@redhat.com> writes:

> Il mar 12 nov 2024, 03:47 Junjie Mao <junjie.mao@hotmail.com> ha scritto:
>
>  I agree that storing generated stuff in the source directory should not
>  be encouraged.
>
>  Just want to mention that such changes can lead to trouble to
>  rust-analyzer. Today there are two ways to inform rust-analyzer of the
>  project structure:
>
>    1. Use rust/Cargo.toml. In this case we'll hit an issue in
>    rust-analyzer [1] that prevents it from including sources outside the
>    crate directory. Thus, definitions in the bindgen-generated code
>    cannot be found.
>
>    2. Use the meson-generated rust-project.json. Due to the use of
>    structured_sources(), that json file refers to the copied sources of
>    qemu-api in the build directory. Rust-analyzer can find every symbol
>    in the qemu-api crate but will jump to those copied files, making it a
>    bit more annoying when developing the crate.
>
> Would it help to move the bindgen-generated code to a completely separate 
> crate (e.g. qemu-api-sys), and avoid structured_sources for qemu-api? It 
> might even help build times.

I just noticed that rust-analyzer is able to include files under
OUT_DIR. With the following changes, rust-analyzer under meson devenv
works nicely:

  1. Rust-analyzer refers to rust/qemu-api/src/* unless the definition
  is in bindings.inc.rs.

  2. No manual copy / symbolic link required, neither bindings.inc.rs
  nor rust-project.json.

The bindgen-generated file is renamed to bindings.inc.rs only because
rust-analyzer seems to refuse including a file without the .rs suffix.

That's at the cost of another file copy, though.

--- diff starts here ---

diff --git a/meson.build b/meson.build
index 1239f5c48c..8cea09ffe1 100644
--- a/meson.build
+++ b/meson.build
@@ -4,6 +4,7 @@ project('qemu', ['c'], meson_version: '>=1.5.0',
         version: files('VERSION'))

 meson.add_devenv({ 'MESON_BUILD_ROOT' : meson.project_build_root() })
+meson.add_devenv({ 'CARGO_TARGET_DIR' : meson.project_build_root() / 'cargo' })

 add_test_setup('quick', exclude_suites: ['slow', 'thorough'], is_default: true)
 add_test_setup('slow', exclude_suites: ['thorough'], env: ['G_TEST_SLOW=1', 
'SPEED=slow'])
@@ -4083,7 +4084,7 @@ if have_rust
   bindings_rs = rust.bindgen(
     input: 'rust/wrapper.h',
     dependencies: common_ss.all_dependencies(),
-    output: 'bindings.rs.inc',
+    output: 'bindings.inc.rs',
     include_directories: include_directories('.', 'include'),
     bindgen_version: ['>=0.60.0'],
     args: bindgen_args,
diff --git a/rust/qemu-api/build.rs b/rust/qemu-api/build.rs
index d7b6d76828..1de86c721b 100644
--- a/rust/qemu-api/build.rs
+++ b/rust/qemu-api/build.rs
@@ -2,17 +2,17 @@
 // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
 // SPDX-License-Identifier: GPL-2.0-or-later

-use std::{env, path::Path};
+use std::{env, fs::copy, io::Result, path::Path};

 use version_check as rustc;

-fn main() {
+fn main() -> Result<()> {
     // Placing bindings.rs.inc in the source directory is supported
     // but not documented or encouraged.
     let path = env::var("MESON_BUILD_ROOT")
         .unwrap_or_else(|_| format!("{}/src", env!("CARGO_MANIFEST_DIR")));

-    let file = format!("{}/bindings.rs.inc", path);
+    let file = format!("{}/bindings.inc.rs", path);
     if !Path::new(&file).exists() {
         panic!(concat!(
             "\n",
@@ -24,7 +24,9 @@ fn main() {
         ));
     }

-    println!("cargo:rustc-env=BINDINGS_RS_INC={}", file);
+    let out_dir = env::var("OUT_DIR").unwrap();
+    let dest_path = format!("{}/bindings.inc.rs", out_dir);
+    copy(&file, Path::new(&dest_path))?;

     // Check for available rustc features
     if rustc::is_min_version("1.77.0").unwrap_or(false) {
@@ -32,4 +34,6 @@ fn main() {
     }

     println!("cargo:rerun-if-changed=build.rs");
+
+    Ok(())
 }
diff --git a/rust/qemu-api/src/bindings.rs b/rust/qemu-api/src/bindings.rs
index 972b1f1ee9..8a9b821bb9 100644
--- a/rust/qemu-api/src/bindings.rs
+++ b/rust/qemu-api/src/bindings.rs
@@ -16,10 +16,10 @@
 )]

 #[cfg(MESON)]
-include!("bindings.rs.inc");
+include!("bindings.inc.rs");

 #[cfg(not(MESON))]
-include!(env!("BINDINGS_RS_INC"));
+include!(concat!(env!("OUT_DIR"), "/bindings.inc.rs"));

 unsafe impl Send for Property {}
 unsafe impl Sync for Property {}

--
Best Regards
Junjie Mao

>
> Paolo
>
>  We can perhaps leave it as a separate topic for another series.
>
>  [1] https://github.com/rust-lang/rust-analyzer/issues/17040
>