builtin: add Os.Env

Author: Defelo

src/par/builtin/Builtin.par

@@ -308,6 +308,7 @@ dec Os.TraverseDir : [Os.Path] Result<Os.Error, recursive either {
   .dir(Os.Path, self) self,
 }>
 
+dec Os.Env : List<(Bytes) Bytes>
 
 /// Url
 

src/par/builtin/os.rs

@@ -156,6 +156,15 @@ pub fn external_module() -> Module<std::sync::Arc<process::Expression<()>>> {
                 ),
                 |handle| Box::pin(os_traverse_dir(handle)),
             ),
+            Definition::external(
+                "Env",
+                Type::name(
+                    Some("List"),
+                    "List",
+                    vec![Type::pair(Type::bytes(), Type::bytes())],
+                ),
+                |handle| Box::pin(os_env(handle)),
+            ),
         ],
     }
 }
@@ -565,6 +574,17 @@ async fn os_traverse_dir(mut handle: Handle) {
     }
 }
 
+async fn os_env(mut handle: Handle) {
+    for (name, value) in std::env::vars_os() {
+        handle.signal(literal!("item"));
+        let mut pair = handle.send();
+        pair.send().provide_bytes(os_to_bytes(&name));
+        pair.provide_bytes(os_to_bytes(&value));
+    }
+    handle.signal(literal!("end"));
+    handle.break_();
+}
+
 async fn pathbuf_from_os_path(mut handle: Handle) -> PathBuf {
     handle.signal(literal!("absolute"));
     let path_bytes = handle.bytes().await;