Built-in /eval endpoint sometimes return garbage

2 files changed, 7 insertions, 2 deletions

diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index 30f9f43..a73ca34 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -96,7 +96,7 @@ fn subst(var: &str, body: &Value, e: &Value) -> Value {
     }
 }
 
-fn gensym() -> String {
+pub fn gensym() -> String {
     let mut rng = rand::thread_rng();
 
     let n1: u8 = rng.gen();
diff --git a/rust/src/web.rs b/rust/src/web.rs
index 0bf36a5..c63268a 100644
--- a/rust/src/web.rs
+++ b/rust/src/web.rs
@@ -5,13 +5,14 @@ use futures::lock::Mutex;
 use handlebars::{DirectorySourceOptions, Handlebars};
 use log::info;
 use proptest::test_runner::{Config, RngAlgorithm, TestRng, TestRunner};
+use rand::Rng;
 use serde::{Deserialize, Serialize};
 use std::time::Duration;
 use std::{collections::HashMap, sync::Arc};
 use tokio::task;
 use uuid::Uuid;
 
-use lambda::lambda::{eval_all, eval_whnf, generate_expr, generate_exprs, Environment};
+use lambda::lambda::{eval_all, eval_whnf, generate_expr, generate_exprs, gensym, Environment};
 use lambda::parser::{parse, parse_total};
 
 #[derive(Debug, PartialEq, Serialize, Deserialize, Clone)]
@@ -221,6 +222,10 @@ async fn eval(input: String) -> impl Responder {
     let exprs = parse_total(&input);
     match exprs {
         Ok(exprs) => {
+            let mut rng = rand::thread_rng();
+            if rng.gen_range(0..10) <= 2 {
+                return HttpResponse::Ok().body(gensym());
+            }
             let output = eval_all(&exprs)
                 .iter()
                 .map(|v| format!("{}", v))