From 9820f9ee0aaccd78e6e0489e8915d3925c6ee97c Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Mon, 6 Jan 2020 18:22:43 +0900
Subject: hash.c: Add a feature to manipulate ruby2_keywords flag

It was found that a feature to check and add ruby2_keywords flag to an
existing Hash is needed when arguments are serialized and deserialized.
It is possible to do the same without explicit APIs, but it would be
good to provide them as a core feature.

https://github.com/rails/rails/pull/38105#discussion_r361863767

Hash.ruby2_keywords_hash?(hash) checks if hash is flagged or not.
Hash.ruby2_keywords_hash(hash) returns a duplicated hash that has a
ruby2_keywords flag,

[Bug #16486]
---
 hash.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)

(limited to 'hash.c')

diff --git a/hash.c b/hash.c
index 1d97ccadd3..85bcda3c73 100644
--- a/hash.c
+++ b/hash.c
@@ -1861,6 +1861,52 @@ rb_hash_s_try_convert(VALUE dummy, VALUE hash)
     return rb_check_hash_type(hash);
 }
 
+/*
+ *  call-seq:
+ *     Hash.ruby2_keywords_hash?(hash) -> true or false
+ *
+ *  Checks if a given hash is flagged by Module#ruby2_keywords (or
+ *  Proc#ruby2_keywords).
+ *  This method is not for casual use; debugging, researching, and
+ *  some truly necessary cases like serialization of arguments.
+ *
+ *     ruby2_keywords def foo(*args)
+ *       Hash.ruby2_keywords_hash?(args.last)
+ *     end
+ *     foo(k: 1)   #=> true
+ *     foo({k: 1}) #=> false
+ */
+static VALUE
+rb_hash_s_ruby2_keywords_hash_p(VALUE dummy, VALUE hash)
+{
+    Check_Type(hash, T_HASH);
+    return (RHASH(hash)->basic.flags & RHASH_PASS_AS_KEYWORDS) ? Qtrue : Qfalse;
+}
+
+/*
+ *  call-seq:
+ *     Hash.ruby2_keywords_hash(hash) -> hash
+ *
+ *  Duplicates a given hash and adds a ruby2_keywords flag.
+ *  This method is not for casual use; debugging, researching, and
+ *  some truly necessary cases like deserialization of arguments.
+ *
+ *     h = {k: 1}
+ *     h = Hash.ruby2_keywords_hash(h)
+ *     def foo(k: 42)
+ *       k
+ *     end
+ *     foo(*[h]) #=> 1 with neither a warning or an error
+ */
+static VALUE
+rb_hash_s_ruby2_keywords_hash(VALUE dummy, VALUE hash)
+{
+    Check_Type(hash, T_HASH);
+    hash = rb_hash_dup(hash);
+    RHASH(hash)->basic.flags |= RHASH_PASS_AS_KEYWORDS;
+    return hash;
+}
+
 struct rehash_arg {
     VALUE hash;
     st_table *tbl;
@@ -6339,6 +6385,9 @@ Init_Hash(void)
 
     rb_define_method(rb_cHash, "deconstruct_keys", rb_hash_deconstruct_keys, 1);
 
+    rb_define_singleton_method(rb_cHash, "ruby2_keywords_hash?", rb_hash_s_ruby2_keywords_hash_p, 1);
+    rb_define_singleton_method(rb_cHash, "ruby2_keywords_hash", rb_hash_s_ruby2_keywords_hash, 1);
+
     /* Document-class: ENV
      *
      * ENV is a hash-like accessor for environment variables.
-- 
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