write complement test result summary to a tsv file

xtask/src/complement.rs

@@ -1,9 +1,13 @@
-use std::path::PathBuf;
+use std::{
+    fs::{self},
+    path::{Path, PathBuf},
+};
 
-use miette::{IntoDiagnostic, Result, WrapErr};
+use miette::{miette, IntoDiagnostic, Result, WrapErr};
 use xshell::{cmd, Shell};
 
 mod docker;
+mod summary;
 mod test2json;
 
 use self::{
@@ -12,23 +16,59 @@ use self::{
 };
 
 #[derive(clap::Args)]
-pub(crate) struct Args;
+pub(crate) struct Args {
+    /// Directory to write test results
+    ///
+    /// This directory will be created automatically, but it must be empty.
+    /// If it exists and is not empty, an error will be returned.
+    #[clap(short, long)]
+    out: PathBuf,
+}
 
 #[allow(clippy::needless_pass_by_value)]
-pub(crate) fn main(_args: Args) -> Result<()> {
+pub(crate) fn main(args: Args) -> Result<()> {
     let sh = Shell::new().unwrap();
     let toplevel = get_toplevel_path(&sh)
         .wrap_err("failed to determine repository root directory")?;
+    create_out_dir(&args.out).wrap_err_with(|| {
+        format!("error initializing output directory {:?}", args.out)
+    })?;
     let docker_image = load_docker_image(&sh, &toplevel).wrap_err(
         "failed to build and load complement-grapevine docker image",
     )?;
     let test_count = count_complement_tests(&sh, &docker_image)
         .wrap_err("failed to determine total complement test count")?;
-    run_complement(&sh, &docker_image, test_count)
+    run_complement(&sh, &args.out, &docker_image, test_count)
         .wrap_err("failed to run complement tests")?;
     Ok(())
 }
 
+/// Ensures that output directory exists and is empty
+///
+/// If the directory does not exist, it will be created. If it is not empty, an
+/// error will be returned.
+///
+/// We have no protection against concurrent programs modifying the contents of
+/// the directory while the complement wrapper tool is running.
+fn create_out_dir(out: &Path) -> Result<()> {
+    fs::create_dir_all(out)
+        .into_diagnostic()
+        .wrap_err("error creating output directory")?;
+    let mut entries = fs::read_dir(out)
+        .into_diagnostic()
+        .wrap_err("error checking current contents of output directory")?;
+    if entries.next().is_some() {
+        return Err(miette!(
+            "output directory is not empty. Refusing to run, instead of \
+             possibly overwriting existing files."
+        ));
+    }
+    fs::create_dir(out.join("logs"))
+        .into_diagnostic()
+        .wrap_err("error creating logs subdirectory in output directory")?;
+    Ok(())
+}
+
 /// Returns the path to the repository root
 fn get_toplevel_path(sh: &Shell) -> Result<PathBuf> {
     let path =