rslib: auto-format protobuf code

prost-build doesn't generate rustfmt-safe code, so we had to add it to
the ignore list for rustfmt on "make check". However, the ignore list
isn't supported by stable rustfmt, so we have to work around this some
other way -- in this case, just do "rustfmt" on the generated file in
"build.rs" (this way, formatting errors in checked-in source code are
still caught but generated code doesn't cause spurrious errors).

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

rslib/build.rs

@@ -1,6 +1,7 @@
 use std::fmt::Write;
 use std::fs;
 use std::path::Path;
+use std::process::Command;
 
 use fluent_syntax::ast::{Entry::Message, ResourceEntry};
 use fluent_syntax::parser::parse;
@@ -200,15 +201,20 @@ fn main() -> std::io::Result<()> {
     fs::write(rust_string_path, rust_string_vec(&idents))?;
 
     // output protobuf generated code
-    // we avoid default OUT_DIR for now, as it breaks code completion
-    std::env::set_var("OUT_DIR", "src");
     println!("cargo:rerun-if-changed=../proto/backend.proto");
-
     let mut config = prost_build::Config::new();
-    config.service_generator(service_generator());
     config
+        // we avoid default OUT_DIR for now, as it breaks code completion
+        .out_dir("src")
+        .service_generator(service_generator())
         .compile_protos(&["../proto/backend.proto"], &["../proto"])
         .unwrap();
+    // rustfmt the protobuf code
+    let rustfmt = Command::new("rustfmt")
+        .arg(Path::new("src/backend_proto.rs"))
+        .status()
+        .unwrap();
+    assert!(rustfmt.success(), "rustfmt backend_proto.rs failed");
 
     // write the other language ftl files
     let mut ftl_lang_dirs = vec!["./ftl/repo/core".to_string()];

rslib/rustfmt.toml

@@ -1 +0,0 @@
-ignore = ["backend_proto.rs"]