Use fixed seeds with ahash

src/app_state.rs

@@ -1,4 +1,3 @@
-use ahash::{HashSet, HashSetExt};
 use anyhow::{bail, Context, Error, Result};
 use std::{
     fs::{self, File},
@@ -11,6 +10,7 @@ use std::{
 use crate::{
     clear_terminal,
     cmd::CmdRunner,
+    collections::hash_set_with_capacity,
     embedded::EMBEDDED_FILES,
     exercise::{Exercise, RunnableExercise},
     info_file::ExerciseInfo,
@@ -70,7 +70,7 @@ impl AppState {
             return StateFileStatus::NotRead;
         }
 
-        let mut done_exercises = HashSet::with_capacity(self.exercises.len());
+        let mut done_exercises = hash_set_with_capacity(self.exercises.len());
 
         for done_exerise_name in lines {
             if done_exerise_name.is_empty() {

src/collections.rs

@@ -0,0 +1,10 @@
+use ahash::AHasher;
+use std::hash::BuildHasherDefault;
+
+/// DOS attacks aren't a concern for Rustlings. Therefore, we use `ahash` with fixed seeds.
+pub type HashSet<T> = std::collections::HashSet<T, BuildHasherDefault<AHasher>>;
+
+#[inline]
+pub fn hash_set_with_capacity<T>(capacity: usize) -> HashSet<T> {
+    HashSet::with_capacity_and_hasher(capacity, BuildHasherDefault::<AHasher>::default())
+}

src/dev/check.rs

@@ -1,4 +1,3 @@
-use ahash::{HashSet, HashSetExt};
 use anyhow::{anyhow, bail, Context, Error, Result};
 use std::{
     cmp::Ordering,
@@ -12,6 +11,7 @@ use std::{
 use crate::{
     cargo_toml::{append_bins, bins_start_end_ind, BINS_BUFFER_CAPACITY},
     cmd::CmdRunner,
+    collections::{hash_set_with_capacity, HashSet},
     exercise::{RunnableExercise, OUTPUT_CAPACITY},
     info_file::{ExerciseInfo, InfoFile},
     CURRENT_FORMAT_VERSION,
@@ -50,8 +50,8 @@ fn check_cargo_toml(
 
 // Check the info of all exercises and return their paths in a set.
 fn check_info_file_exercises(info_file: &InfoFile) -> Result<HashSet<PathBuf>> {
-    let mut names = HashSet::with_capacity(info_file.exercises.len());
-    let mut paths = HashSet::with_capacity(info_file.exercises.len());
+    let mut names = hash_set_with_capacity(info_file.exercises.len());
+    let mut paths = hash_set_with_capacity(info_file.exercises.len());
 
     let mut file_buf = String::with_capacity(1 << 14);
     for exercise_info in &info_file.exercises {
@@ -251,7 +251,7 @@ fn check_solutions(
             })
             .collect::<Vec<_>>();
 
-        let mut sol_paths = HashSet::with_capacity(info_file.exercises.len());
+        let mut sol_paths = hash_set_with_capacity(info_file.exercises.len());
         let mut fmt_cmd = Command::new("rustfmt");
         fmt_cmd
             .arg("--check")

src/main.rs

@@ -13,6 +13,7 @@ use self::{app_state::AppState, dev::DevCommands, info_file::InfoFile, watch::Wa
 mod app_state;
 mod cargo_toml;
 mod cmd;
+mod collections;
 mod dev;
 mod embedded;
 mod exercise;