From 55eefa45fc8436a338d125ddf9ba0d1aa9e04b45 Mon Sep 17 00:00:00 2001
From: Philip Ross <dev@baseballlover723.com>
Date: Sat, 22 Jul 2023 06:19:38 -0700
Subject: [PATCH] Add yield `key` in `Hash#transform_values` and `value` in
 `#transform_keys` (#13608)

---
 spec/std/hash_spec.cr | 21 +++++++++++++++++++++
 src/hash.cr           | 23 +++++++++++++++--------
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/spec/std/hash_spec.cr b/spec/std/hash_spec.cr
index 85a3ad2833f8..66f9c7a9adee 100644
--- a/spec/std/hash_spec.cr
+++ b/spec/std/hash_spec.cr
@@ -882,6 +882,13 @@ describe "Hash" do
     h2.should be_empty
   end
 
+  it "transforms keys with values included" do
+    h1 = {1 => "a", 2 => "b", 3 => "c"}
+
+    h2 = h1.transform_keys { |k, v| "#{k}#{v}" }
+    h2.should eq({"1a" => "a", "2b" => "b", "3c" => "c"})
+  end
+
   it "transforms values" do
     h1 = {"a" => 1, "b" => 2, "c" => 3}
 
@@ -905,6 +912,13 @@ describe "Hash" do
     h2.should be_empty
   end
 
+  it "transforms values with keys included" do
+    h1 = {"a" => 1, "b" => 2, "c" => 3}
+
+    h2 = h1.transform_values { |v, k| "#{k}#{v}" }
+    h2.should eq({"a" => "a1", "b" => "b2", "c" => "c3"})
+  end
+
   it "transform values in place" do
     h = {"a" => 1, "b" => 2, "c" => 3}
 
@@ -912,6 +926,13 @@ describe "Hash" do
     h.should eq({"a" => 2, "b" => 3, "c" => 4})
   end
 
+  it "transform values in place with keys included" do
+    h = {"a" => "1", "b" => "2", "c" => "3"}
+
+    h.transform_values! { |v, k| "#{k}#{v}" }
+    h.should eq({"a" => "a1", "b" => "b2", "c" => "c3"})
+  end
+
   it "zips" do
     ary1 = [1, 2, 3]
     ary2 = ['a', 'b', 'c']
diff --git a/src/hash.cr b/src/hash.cr
index 10a1eb4db23b..05ea0ca3b1de 100644
--- a/src/hash.cr
+++ b/src/hash.cr
@@ -1706,42 +1706,49 @@ class Hash(K, V)
 
   # Returns a new hash with all keys converted using the block operation.
   # The block can change a type of keys.
+  # The block yields the key and value.
   #
   # ```
   # hash = {:a => 1, :b => 2, :c => 3}
-  # hash.transform_keys { |key| key.to_s } # => {"a" => 1, "b" => 2, "c" => 3}
+  # hash.transform_keys { |key| key.to_s }                # => {"a" => 1, "b" => 2, "c" => 3}
+  # hash.transform_keys { |key, value| key.to_s * value } # => {"a" => 1, "bb" => 2, "ccc" => 3}
   # ```
-  def transform_keys(& : K -> K2) : Hash(K2, V) forall K2
+  def transform_keys(& : K, V -> K2) : Hash(K2, V) forall K2
     each_with_object({} of K2 => V) do |(key, value), memo|
-      memo[yield(key)] = value
+      memo[yield(key, value)] = value
     end
   end
 
   # Returns a new hash with the results of running block once for every value.
   # The block can change a type of values.
+  # The block yields the value and key.
   #
   # ```
   # hash = {:a => 1, :b => 2, :c => 3}
-  # hash.transform_values { |value| value + 1 } # => {:a => 2, :b => 3, :c => 4}
+  # hash.transform_values { |value| value + 1 }             # => {:a => 2, :b => 3, :c => 4}
+  # hash.transform_values { |value, key| "#{key}#{value}" } # => {:a => "a1", :b => "b2", :c => "c3"}
   # ```
-  def transform_values(& : V -> V2) : Hash(K, V2) forall V2
+  def transform_values(& : V, K -> V2) : Hash(K, V2) forall V2
     each_with_object({} of K => V2) do |(key, value), memo|
-      memo[key] = yield(value)
+      memo[key] = yield(value, key)
     end
   end
 
   # Destructively transforms all values using a block. Same as transform_values but modifies in place.
   # The block cannot change a type of values.
+  # The block yields the value and key.
   #
   # ```
   # hash = {:a => 1, :b => 2, :c => 3}
   # hash.transform_values! { |value| value + 1 }
   # hash # => {:a => 2, :b => 3, :c => 4}
+  # hash.transform_values! { |value, key| value + key.to_s[0].ord }
+  # hash # => {:a => 99, :b => 101, :c => 103}
   # ```
   # See `#update` for updating a *single* value.
-  def transform_values!(& : V -> V) : self
+  def transform_values!(& : V, K -> V) : self
     each_entry_with_index do |entry, i|
-      new_value = yield entry.value
+      new_value = yield entry.value, entry.key
       set_entry(i, Entry(K, V).new(entry.hash, entry.key, new_value))
     end
     self