run format_exercises.sh in parallel (#2031)

bin/format_exercises.sh

@@ -5,29 +5,33 @@ set -eo pipefail
 
 repo=$(git rev-parse --show-toplevel)
 
+echo "Formatting exercise files..."
+
+format_one_exercise() {
+    exercise_dir="$1"
+    source_file_name="$2"
+
+    cd "$exercise_dir"
+    config_file="$exercise_dir/.meta/config.json"
+    if jq --exit-status '.custom?."allowed-to-not-compile"?' "$config_file" &> /dev/null; then
+        exit 0
+    fi
+    cargo fmt
+    file_name=".meta/$source_file_name.rs"
+    if [ -f "$file_name" ]; then
+        rustfmt "$file_name"
+    fi
+}
+
 # traverse either concept or practice exercise
 # directory and format Rust files
 format_exercises() {
     exercises_path="$repo/exercises/$1"
     source_file_name="$2"
     for exercise_dir in "$exercises_path"/*; do
-        (
-        cd "$exercise_dir"
-        config_file="$exercise_dir/.meta/config.json"
-        if jq --exit-status '.custom?."allowed-to-not-compile"?' "$config_file"; then
-            exercise=$(basename "$exercise_dir")
-            echo "$exercise's stub is allowed to not compile"
-            # exit the subshell successfully to continue
-            # to the next exercise directory
-            exit 0
-        fi
-        cargo fmt
-        file_name=".meta/$source_file_name.rs"
-        if [ -f "$file_name" ]; then
-            rustfmt "$file_name"
-        fi
-    )
+        format_one_exercise "$exercise_dir" "$source_file_name" &
     done
+    wait
 }
 # https://github.com/exercism/docs/blob/main/anatomy/tracks/concept-exercises.md#file-exemplar-implementation
 format_exercises "concept" "exemplar"

justfile

@@ -21,7 +21,7 @@ test:
     ./bin/check_exercises.sh
     CLIPPY=true ./bin/check_exercises.sh
     cd rust-tooling && cargo test
-    # TODO format exercises
+    ./bin/format_exercises.sh ; git diff --exit-code
 
 add-exercise *args="":
     cd rust-tooling/generate; cargo run --quiet --release -- add {{ args }}