tests: check set of files passed to diff-editor in jj edit

testing/fake-diff-editor.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use std::collections::HashSet;
 use std::path::PathBuf;
 use std::process::exit;
 
@@ -29,6 +30,22 @@ struct Args {
     after: PathBuf,
 }
 
+fn files_recursively(dir: &PathBuf) -> HashSet<String> {
+    let mut files = HashSet::new();
+    for dir_entry in std::fs::read_dir(dir).unwrap() {
+        let dir_entry = dir_entry.unwrap();
+        let base_name = dir_entry.file_name().to_str().unwrap().to_string();
+        if dir_entry.path().is_dir() {
+            for sub_path in files_recursively(&dir_entry.path()) {
+                files.insert(format!("{base_name}/{sub_path}"));
+            }
+        } else {
+            files.insert(base_name);
+        }
+    }
+    files
+}
+
 fn main() {
     let args: Args = Args::parse();
     let edit_script_path = PathBuf::from(std::env::var_os("EDIT_SCRIPT").unwrap());
@@ -39,6 +56,28 @@ fn main() {
         match parts.as_slice() {
             [""] => {}
             ["fail"] => exit(1),
+            ["files-before", ..] => {
+                let expected = parts[1..].iter().copied().map(str::to_string).collect();
+                let actual = files_recursively(&args.before);
+                if actual != expected {
+                    eprintln!(
+                        "unexpected files before: {:?}",
+                        actual.iter().sorted().collect_vec()
+                    );
+                    exit(1)
+                }
+            }
+            ["files-after", ..] => {
+                let expected = parts[1..].iter().copied().map(str::to_string).collect();
+                let actual = files_recursively(&args.after);
+                if actual != expected {
+                    eprintln!(
+                        "unexpected files after: {:?}",
+                        actual.iter().sorted().collect_vec()
+                    );
+                    exit(1)
+                }
+            }
             ["rm", file] => {
                 std::fs::remove_file(args.after.join(file)).unwrap();
             }

tests/test_edit_command.rs

@@ -32,7 +32,11 @@ fn test_edit() {
     let edit_script = test_env.set_up_fake_diff_editor();
 
     // Nothing happens if we make no changes
-    std::fs::write(&edit_script, "").unwrap();
+    std::fs::write(
+        &edit_script,
+        "files-before file1 file2\0files-after JJ-INSTRUCTIONS file2",
+    )
+    .unwrap();
     let stdout = test_env.jj_cmd_success(&repo_path, &["edit"]);
     insta::assert_snapshot!(stdout, @"Nothing changed.
 ");