Use a faster, deterministic RNG in the string escape tests

This shaves about 9 seconds off of the runtime, and makes the test
deterministic.

We do not touch the test_convert test because there is a known failure and we
need to track it down before making it deterministic.

fish-rust/Cargo.lock

@@ -347,6 +347,7 @@ dependencies = [
  "pcre2",
  "printf-compat",
  "rand",
+ "rand_pcg",
  "rsconf",
  "unixstring",
  "widestring",
@@ -789,6 +790,15 @@ dependencies = [
  "getrandom",
 ]
 
+[[package]]
+name = "rand_pcg"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59cad018caf63deb318e5a4586d99a24424a364f40f1e5778c29aca23f4fc73e"
+dependencies = [
+ "rand_core",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.3.5"

fish-rust/Cargo.toml

@@ -28,6 +28,7 @@ once_cell = "1.17.0"
 rand = { version = "0.8.5", features = ["small_rng"] }
 unixstring = "0.2.7"
 widestring = "1.0.2"
+rand_pcg = "0.3.1"
 
 [build-dependencies]
 autocxx-build = "0.23.1"

fish-rust/src/tests/string_escape.rs

@@ -5,7 +5,9 @@ use crate::common::{
 };
 use crate::wchar::{widestrs, wstr, WString};
 use crate::wutil::encoding::{wcrtomb, zero_mbstate, AT_LEAST_MB_LEN_MAX};
-use rand::random;
+use rand::SeedableRng;
+use rand::{Rng, RngCore};
+use rand_pcg::Pcg64Mcg;
 
 /// wcs2string is locale-dependent, so ensure we have a multibyte locale
 /// before using it in a test.
@@ -99,15 +101,19 @@ fn test_escape_var() {
 
 #[widestrs]
 #[test]
-fn test_escape_crazy() {
+fn test_escape_random() {
     setlocale();
+    let seed: u128 = 92348567983274852905629743984572;
+    let mut rng = Pcg64Mcg::new(seed);
+
     let mut random_string = WString::new();
     let mut escaped_string;
     for _ in 0..(ESCAPE_TEST_COUNT as u32) {
         random_string.clear();
-        while random::<usize>() % ESCAPE_TEST_LENGTH != 0 {
+        let length = rng.gen_range(0..=(2 * ESCAPE_TEST_LENGTH));
+        for _ in 0..length {
             random_string
-                .push(char::from_u32((random::<u32>() % ESCAPE_TEST_CHAR as u32) + 1).unwrap());
+                .push(char::from_u32((rng.next_u32() % ESCAPE_TEST_CHAR as u32) + 1).unwrap());
         }
 
         for (escape_style, unescape_style) in [
@@ -157,6 +163,7 @@ fn str2hex(input: &[u8]) -> String {
 /// string comes back through double conversion.
 #[test]
 fn test_convert() {
+    use rand::random;
     for _ in 0..ESCAPE_TEST_COUNT {
         let mut origin: Vec<u8> = vec![];
         while (random::<usize>() % ESCAPE_TEST_LENGTH) != 0 {