Test Env::{nth, count, last} overrides

src/test/run-pass/env-vars-iter.rs

@@ -0,0 +1,68 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::process::Command;
+use std::env;
+
+fn check_var(&(ref key, ref val): &(String, String)) -> bool {
+    match &**key {
+        "FOO" => { assert_eq!(val, "BAR"); true },
+        "BAR" => { assert_eq!(val, "BAZ"); true },
+        "BAZ" => { assert_eq!(val, "FOO"); true },
+        _ => false,
+    }
+}
+
+fn main() {
+    if let Some(arg) = env::args().nth(1) {
+        match &*arg {
+            "empty" => {
+                assert_eq!(env::vars().count(), 0);
+                assert_eq!(env::vars().next(), None);
+                assert_eq!(env::vars().nth(1), None);
+                assert_eq!(env::vars().last(), None);
+            },
+            "many" => {
+                assert!(env::vars().count() >= 3);
+                assert!(env::vars().last().is_some());
+                assert_eq!(env::vars().filter(check_var).count(), 3);
+                assert_eq!(
+                    (0..env::vars().count())
+                        .map(|i| env::vars().nth(i).unwrap())
+                        .filter(check_var)
+                        .count(),
+                    3);
+            },
+            arg => {
+                panic!("Unexpected arg {}", arg);
+            },
+        }
+    } else {
+        // Command::env_clear does not work on Windows.
+        // https://github.com/rust-lang/rust/issues/31259
+        if !cfg!(windows) {
+            let status = Command::new(env::current_exe().unwrap())
+                                 .arg("empty")
+                                 .env_clear()
+                                 .status()
+                                 .unwrap();
+            assert_eq!(status.code(), Some(0));
+        }
+
+        let status = Command::new(env::current_exe().unwrap())
+                             .arg("many")
+                             .env("FOO", "BAR")
+                             .env("BAR", "BAZ")
+                             .env("BAZ", "FOO")
+                             .status()
+                             .unwrap();
+        assert_eq!(status.code(), Some(0));
+    }
+}