Only write codegen file if there are changes
This avoids rewriting the same contents and needing to recompile syn
when nothing changed.
diff --git a/codegen/src/file.rs b/codegen/src/file.rs
index da7aabe..32bf047 100644
--- a/codegen/src/file.rs
+++ b/codegen/src/file.rs
@@ -1,21 +1,30 @@
use crate::error::Result;
use proc_macro2::TokenStream;
-use std::fs::File;
-use std::io::{BufWriter, Write};
+use std::fs;
+use std::io::Write;
use std::path::Path;
pub fn write<P: AsRef<Path>>(path: P, content: TokenStream) -> Result<()> {
- let mut file = File::create(path).map(BufWriter::new)?;
+ let mut formatted = Vec::new();
write!(
- file,
+ formatted,
"// THIS FILE IS AUTOMATICALLY GENERATED; DO NOT EDIT\n\n"
)?;
+
let mut config = rustfmt::Config::default();
config.set().emit_mode(rustfmt::EmitMode::Stdout);
config.set().verbose(rustfmt::Verbosity::Quiet);
config.set().format_macro_matchers(true);
config.set().normalize_doc_attributes(true);
- let mut session = rustfmt::Session::new(config, Some(&mut file));
+
+ let mut session = rustfmt::Session::new(config, Some(&mut formatted));
session.format(rustfmt::Input::Text(content.to_string()))?;
+ drop(session);
+
+ if path.as_ref().is_file() && fs::read(&path)? == formatted {
+ return Ok(());
+ }
+
+ fs::write(path, formatted)?;
Ok(())
}