From 32acadf7572a79e55c4f6f5c64ad0e2cd7aa5c7a Mon Sep 17 00:00:00 2001
From: Benoit Tigeot <benoit@hopsandfork.com>
Date: Wed, 21 Mar 2018 11:46:30 +0000
Subject: [PATCH] Add slice method to ENV like Hash#slice

---
 hash.c                | 30 ++++++++++++++++++++++++++++++
 test/ruby/test_env.rb | 11 +++++++++++
 2 files changed, 41 insertions(+)

diff --git a/hash.c b/hash.c
index 3a499872ad73..c8125a0d6cc6 100644
--- a/hash.c
+++ b/hash.c
@@ -4067,6 +4067,35 @@ env_keep_if(VALUE ehash)
     return envtbl;
 }
 
+/*
+ *  call-seq:
+ *     ENV.slice(*keys) -> a_hash
+ *
+ *  Returns a hash containing only the given keys from ENV and their values.
+ *
+ *     ENV.slice("TERM","HOME")  #=> {"TERM"=>"xterm-256color", "HOME"=>"/Users/rhc"}
+ */
+static VALUE
+env_slice(int argc, VALUE *argv)
+{
+    int i;
+    VALUE key, value, result;
+
+    if (argc == 0) {
+        return rb_hash_new();
+    }
+    result = rb_hash_new_with_size(argc);
+
+    for (i = 0; i < argc; i++) {
+        key = argv[i];
+        value = rb_f_getenv(Qnil, key);
+        if (value != Qnil)
+            rb_hash_aset(result, key, value);
+    }
+
+    return result;
+}
+
 /*
  * call-seq:
  *   ENV.clear
@@ -4749,6 +4778,7 @@ Init_Hash(void)
     rb_define_singleton_method(envtbl, "delete", env_delete_m, 1);
     rb_define_singleton_method(envtbl, "delete_if", env_delete_if, 0);
     rb_define_singleton_method(envtbl, "keep_if", env_keep_if, 0);
+    rb_define_singleton_method(envtbl, "slice", env_slice, -1);
     rb_define_singleton_method(envtbl, "clear", rb_env_clear, 0);
     rb_define_singleton_method(envtbl, "reject", env_reject, 0);
     rb_define_singleton_method(envtbl, "reject!", env_reject_bang, 0);
diff --git a/test/ruby/test_env.rb b/test/ruby/test_env.rb
index 699f7db084be..2f4923fbd95a 100644
--- a/test/ruby/test_env.rb
+++ b/test/ruby/test_env.rb
@@ -281,6 +281,17 @@ def test_filter
     end
   end
 
+  def test_slice
+    ENV.clear
+    ENV["foo"] = "bar"
+    ENV["baz"] = "qux"
+    ENV["bar"] = "rab"
+    assert_equal({}, ENV.slice())
+    assert_equal({}, ENV.slice(""))
+    assert_equal({}, ENV.slice("unknown"))
+    assert_equal({"foo"=>"bar", "baz"=>"qux"}, ENV.slice("foo", "baz"))
+  end
+
   def test_clear
     ENV.clear
     assert_equal(0, ENV.size)