Add support for -Zunpretty=hir

[jyn514]

This is the first half of #502. Adding support for the AST requires first adding -Zunpretty=ast to the rust compiler (rust-lang/rust#82304).

I want to run rustfmt on the generated code, but I'm not sure how to do that.. This is what I tried so far:

diff --git a/ui/src/sandbox.rs b/ui/src/sandbox.rs
index 838d7a0..5fe4887 100644
--- a/ui/src/sandbox.rs
+++ b/ui/src/sandbox.rs
@@ -150,7 +150,10 @@ impl Sandbox {
             Some(file) => {
                 if CompileTarget::Hir == req.target {
                     // Run rustfmt on the generated HIR.
-                    format_command(req).arg(file)
+                    let mut rustfmt = self.format_command(req, true);
+                    rustfmt.arg(dbg!(&file));
+                    log::debug!("formatting generated HIR: {:?}", rustfmt);
+                    run_command_with_timeout(rustfmt)?;
                 }
                 read(&file)?.unwrap_or_else(String::new)
             }
@@ -200,7 +203,7 @@ impl Sandbox {
 
     pub fn format(&self, req: &FormatRequest) -> Result<FormatResponse> {
         self.write_source_code(&req.code)?;
-        let command = self.format_command(req);
+        let command = self.format_command(req, false);
 
         let output = run_command_with_timeout(command)?;
 
@@ -356,14 +359,19 @@ impl Sandbox {
         cmd
     }
 
-    fn format_command(&self, req: impl EditionRequest) -> Command {
+    fn format_command(&self, req: impl EditionRequest, single_file: bool) -> Command {
         let crate_type = CrateType::Binary;
 
         let mut cmd = self.docker_command(Some(crate_type));
 
         cmd.apply_edition(req);
 
-        cmd.arg("rustfmt").args(&["cargo", "fmt"]);
+        cmd.arg("rustfmt");
+        if single_file {
+            cmd.arg("rustfmt");
+        } else {
+            cmd.args(&["cargo", "fmt"]);
+        }
 
         log::debug!("Formatting command is {:?}", cmd);

But it didn't actually format the code, I'm not sure what's going wrong. AFAIK rustfmt formats files in places, not to stdout.

[shepmaster]

I want to run rustfmt on the generated code, but I'm not sure how to do that

You won't be able to; not the way you are trying to, at least. Rustfmt is in a completely separate container (there are 6: stable, beta, nightly, miri, clippy, rustfmt). This allows updating the compiler when miri/clippy/rustfmt are broken.

The same general idea is wanted for expanding macros, so any solution may want to attempt to encompass that, but I expect that the easiest way is to make a second request from the frontend.

[jyn514]

You won't be able to; not the way you are trying to, at least. Rustfmt is in a completely separate container (there are 6: stable, beta, nightly, miri, clippy, rustfmt). This allows updating the compiler when miri/clippy/rustfmt are broken.

Hmm, maybe I could do it by feeding the input to rustfmt on stdin instead of trying to use the same files between containers? I don't think the run_command_with_timeout API allows for that though, to write to stdin I need to have a Child handle: https://doc.rust-lang.org/std/process/struct.Stdio.html#method.piped

[jyn514]

FWIW, I think this would be useful to land as is, and I can try to add rustfmt in a follow-up PR.

[jyn514]

@shepmaster this is ready for re-review.

[jyn514]

🎉