add random seed generation

Author: jfmontanaro

Cargo.lock

@@ -11,6 +11,7 @@ members = [
     "crates/roc_stdio",
     "crates/roc_env",
     "crates/roc_sqlite",
+    "crates/roc_random",
 ]
 
 [workspace.package]
@@ -37,6 +38,7 @@ roc_http = { path = "crates/roc_http" }
 roc_io_error = { path = "crates/roc_io_error" }
 roc_stdio = { path = "crates/roc_stdio" }
 roc_env = { path = "crates/roc_env" }
+roc_random = { path = "crates/roc_random" }
 roc_sqlite = { path = "crates/roc_sqlite" }
 memchr = "=2.7.4"
 hyper = { version = "=1.6.0", default-features = false, features = [
@@ -61,3 +63,4 @@ libc = "=0.2.172"
 backtrace = "=0.3.75"
 libsqlite3-sys = { version = "=0.33.0", features = ["bundled"] }
 thread_local = "=1.1.8"
+getrandom = { version = "0.3.3", features = [ "std" ] }

Cargo.toml

@@ -0,0 +1,19 @@
+#!/usr/bin/expect
+
+# uncomment line below for debugging
+# exp_internal 1
+
+set timeout 7
+
+source ./ci/expect_scripts/shared-code.exp
+
+spawn $env(EXAMPLES_DIR)random-seed
+
+expect -re "Seed is: \\d+" {
+    expect eof {
+        check_exit_and_segfault
+    }
+}
+
+puts stderr "\nExpect script failed: output was different from expected value. uncomment `exp_internal 1` to debug."
+exit 1

ci/expect_scripts/random.exp

@@ -27,10 +27,11 @@ roc_io_error.workspace = true
 roc_http.workspace = true
 roc_stdio.workspace = true
 roc_env.workspace = true
+roc_random.workspace = true
 roc_sqlite.workspace = true
 hyper.workspace = true
 hyper-rustls.workspace = true
 tokio.workspace = true
 bytes.workspace = true
 http-body-util.workspace = true
-hyper-util.workspace = true
+hyper-util.workspace = true

crates/roc_host/Cargo.toml

@@ -349,6 +349,7 @@ pub fn init() {
         roc_fx_temp_dir as _,
         roc_fx_get_locale as _,
         roc_fx_get_locales as _,
+        roc_fx_random_seed as _,
         roc_fx_sqlite_bind as _,
         roc_fx_sqlite_column_value as _,
         roc_fx_sqlite_columns as _,
@@ -658,7 +659,7 @@ async fn async_send_request(request: hyper::Request<http_body_util::Full<Bytes>>
 
     let client: Client<_, http_body_util::Full<Bytes>> =
         Client::builder(TokioExecutor::new()).build(https);
-        
+
     let response_res = client.request(request).await;
 
     match response_res {
@@ -809,6 +810,11 @@ pub extern "C" fn roc_fx_get_locales() -> RocList<RocStr> {
     roc_env::get_locales()
 }
 
+#[no_mangle]
+pub extern "C" fn roc_fx_random_seed() -> RocResult<u64, IOErr> {
+    roc_random::seed()
+}
+
 #[no_mangle]
 pub extern "C" fn roc_fx_sqlite_bind(
     stmt: RocBox<()>,

crates/roc_host/src/lib.rs

@@ -0,0 +1,13 @@
+[package]
+name = "roc_random"
+description = "Common functionality for Roc to interface with rand"
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+version.workspace = true
+
+[dependencies]
+roc_std.workspace = true
+roc_io_error.workspace = true
+getrandom.workspace = true

crates/roc_random/Cargo.toml

@@ -0,0 +1,10 @@
+use roc_std::RocResult;
+use roc_io_error::IOErr;
+
+
+pub fn seed() -> RocResult<u64, IOErr> {
+    getrandom::u64()
+        .map_err(|e| std::io::Error::from(e))
+        .map_err(|e| IOErr::from(e))
+        .into()
+}

crates/roc_random/src/lib.rs

@@ -0,0 +1,15 @@
+app [main!] { pf: platform "../platform/main.roc" }
+
+# To run this example: check the README.md in this folder
+
+# Demo of basic-cli Random functions
+
+import pf.Stdout
+import pf.Random
+import pf.Arg exposing [Arg]
+
+main! : List Arg => Result {} _
+main! = |_args|
+    seed = Random.seed!({})?
+
+    Stdout.line!("Seed is: ${Inspect.to_str(seed)}")

examples/random-seed.roc

@@ -33,6 +33,7 @@ hosted [
     hard_link!,
     path_type!,
     posix_time!,
+    random_seed!,
     send_request!,
     set_cwd!,
     sleep_millis!,
@@ -146,3 +147,5 @@ env_dict! : {} => List (Str, Str)
 env_var! : Str => Result Str {}
 exe_path! : {} => Result (List U8) {}
 set_cwd! : List U8 => Result {} {}
+
+random_seed! : {} => Result U64 InternalIOErr.IOErrFromHost

platform/Host.roc

@@ -0,0 +1,20 @@
+module [
+    IOErr,
+    seed!,
+]
+
+import InternalIOErr
+import Host
+
+
+## Tag union of possible errors when getting a random seed.
+##
+## > This is the same as [`File.IOErr`](File#IOErr).
+IOErr : InternalIOErr.IOErr
+
+## Generate a random U64 using the system's source of randomness.
+## This uses the Rust crate `getrandom`.
+seed! : {} => Result U64 [RandomErr IOErr]
+seed! = |{}|
+    Host.random_seed!({})
+    |> Result.map_err(|err| RandomErr(InternalIOErr.handle_err(err)))