1 files changed, 32 insertions, 0 deletions
diff --git a/syn/codegen/src/file.rs b/syn/codegen/src/file.rs
new file mode 100644
index 0000000..5521d75
--- /dev/null
+++ b/syn/codegen/src/file.rs
@@ -0,0 +1,32 @@
+use anyhow::Result;
+use proc_macro2::TokenStream;
+use std::fs;
+use std::io::Write;
+use std::path::Path;
+
+pub fn write<P: AsRef<Path>>(path: P, content: TokenStream) -> Result<()> {
+    let mut formatted = Vec::new();
+    writeln!(
+        formatted,
+        "// This file is @generated by syn-internal-codegen."
+    )?;
+    writeln!(formatted, "// It is not intended for manual editing.")?;
+    writeln!(formatted)?;
+
+    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 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(())
+}