transpile: Run rustfmt on generated .rs files (#1458)

- Fixes #742.

Rather than running `cargo fmt`, this runs the `rustfmt` binary directly
so that it can be used on individual files, and also when there are no
build files.

Author: kkysen

c2rust-transpile/src/build_files/mod.rs

@@ -11,10 +11,10 @@ use serde_json::json;
 
 use super::compile_cmds::LinkCmd;
 use super::TranspilerConfig;
-use crate::get_module_name;
 use crate::CrateSet;
 use crate::ExternCrateDetails;
 use crate::PragmaSet;
+use crate::{get_module_name, rustfmt};
 
 #[derive(Debug, Copy, Clone)]
 pub enum BuildDirectoryContents {
@@ -225,7 +225,13 @@ fn emit_build_rs(
     });
     let output = reg.render("build.rs", &json).unwrap();
     let output_path = build_dir.join("build.rs");
-    maybe_write_to_file(&output_path, output, tcfg.overwrite_existing)
+    let path = maybe_write_to_file(&output_path, output, tcfg.overwrite_existing)?;
+
+    if !tcfg.disable_rustfmt {
+        rustfmt(&output_path, build_dir);
+    }
+
+    Some(path)
 }
 
 /// Emit lib.rs (main.rs) for a library (binary). Returns `Some(path)`
@@ -252,8 +258,13 @@ fn emit_lib_rs(
 
     let output_path = build_dir.join(file_name);
     let output = reg.render("lib.rs", &json).unwrap();
+    let path = maybe_write_to_file(&output_path, output, tcfg.overwrite_existing)?;
+
+    if !tcfg.disable_rustfmt {
+        rustfmt(&output_path, build_dir);
+    }
 
-    maybe_write_to_file(&output_path, output, tcfg.overwrite_existing)
+    Some(path)
 }
 
 /// If we translate variadic functions, the output will only compile

c2rust-transpile/src/lib.rs

@@ -97,6 +97,7 @@ pub struct TranspilerConfig {
     pub output_dir: Option<PathBuf>,
     pub translate_const_macros: TranslateMacros,
     pub translate_fn_macros: TranslateMacros,
+    pub disable_rustfmt: bool,
     pub disable_refactoring: bool,
     pub preserve_unused_functions: bool,
     pub log_level: log::LevelFilter,
@@ -517,14 +518,18 @@ fn reorganize_definitions(
     }
 
     invoke_refactor(build_dir)?;
-    // fix the formatting of the output of `c2rust-refactor`
-    let status = Command::new("cargo")
-        .args(["fmt"])
-        .current_dir(build_dir)
-        .status()?;
-    if !status.success() {
-        warn!("cargo fmt failed, code may not be well-formatted");
+
+    if !tcfg.disable_rustfmt {
+        // fix the formatting of the output of `c2rust-refactor`
+        let status = Command::new("cargo")
+            .args(["fmt"])
+            .current_dir(build_dir)
+            .status()?;
+        if !status.success() {
+            warn!("cargo fmt failed, code may not be well-formatted");
+        }
     }
+
     Ok(())
 }
 
@@ -642,6 +647,10 @@ fn transpile_single(
         ),
     };
 
+    if !tcfg.disable_rustfmt {
+        rustfmt(&output_path, build_dir);
+    }
+
     Ok((output_path, pragmas, crates))
 }
 
@@ -689,3 +698,17 @@ fn get_output_path(
         input_path
     }
 }
+
+fn rustfmt(output_path: &Path, build_dir: &Path) {
+    let edition = "2021";
+
+    let status = Command::new("rustfmt")
+        .args(["--edition", edition])
+        .arg(output_path)
+        .current_dir(build_dir)
+        .status();
+
+    if !status.map_or(false, |status| status.success()) {
+        warn!("rustfmt failed, code may not be well-formatted");
+    }
+}

c2rust-transpile/tests/snapshots.rs

@@ -39,6 +39,7 @@ fn config() -> TranspilerConfig {
         output_dir: None,
         translate_const_macros: Default::default(),
         translate_fn_macros: Default::default(),
+        disable_rustfmt: false,
         disable_refactoring: false,
         preserve_unused_functions: false,
         log_level: log::LevelFilter::Warn,
@@ -91,12 +92,6 @@ fn transpile(platform: Option<&str>, c_path: &Path) {
 
     let edition = "2021";
 
-    let status = Command::new("rustfmt")
-        .args(["--edition", edition])
-        .arg(&rs_path)
-        .status();
-    assert!(status.unwrap().success());
-
     let rs = fs::read_to_string(&rs_path).unwrap();
     let debug_expr = format!("cat {}", rs_path.display());
 

c2rust/src/bin/c2rust-transpile.rs

@@ -145,6 +145,10 @@ struct Args {
     #[clap(long)]
     emit_no_std: bool,
 
+    /// Disable running rustfmt after translation
+    #[clap(long)]
+    disable_rustfmt: bool,
+
     /// Disable running refactoring tool after translation
     #[clap(long)]
     disable_refactoring: bool,
@@ -232,6 +236,7 @@ fn main() {
 
         translate_const_macros: args.translate_const_macros.into(),
         translate_fn_macros: args.translate_fn_macros.into(),
+        disable_rustfmt: args.disable_rustfmt,
         disable_refactoring: args.disable_refactoring,
         preserve_unused_functions: args.preserve_unused_functions,