feat: adding FilterValues and fix FilterKeys signature (#661)

* feat: adding FilterValues and fix FilterKeys signature

* oops

README.md

@@ -147,6 +147,8 @@ Supported helpers for maps:
 - [MapEntries](#mapentries)
 - [MapToSlice](#maptoslice)
 - [FilterMapToSlice](#FilterMapToSlice)
+- [FilterKeys](#FilterKeys)
+- [FilterValues](#FilterValues)
 
 Supported math helpers:
 
@@ -1503,6 +1505,36 @@ result := lo.FilterMapToSlice(kv, func(k int, v int64) (string, bool) {
 // []{"2_2", "4_4"}
 ```
 
+### FilterKeys
+
+Transforms a map into a slice based on predicate returns truthy for specific elements. It is a mix of `lo.Filter()` and `lo.Keys()`.
+
+```go
+kv := map[int]string{1: "foo", 2: "bar", 3: "baz"}
+
+result := FilterKeys(kv, func(k int, v string) bool {
+    return v == "foo"
+})
+// [1]
+```
+
+[[play](https://go.dev/play/p/OFlKXlPrBAe)]
+
+### FilterValues
+
+Transforms a map into a slice based on predicate returns truthy for specific elements. It is a mix of `lo.Filter()` and `lo.Values()`.
+
+```go
+kv := map[int]string{1: "foo", 2: "bar", 3: "baz"}
+
+result := FilterValues(kv, func(k int, v string) bool {
+    return v == "foo"
+})
+// ["foo"]
+```
+
+[[play](https://go.dev/play/p/YVD5r_h-LX-)]
+
 ### Range / RangeFrom / RangeWithSteps
 
 Creates an array of numbers (positive and/or negative) progressing from start up to, but not including end.

intersect_test.go

@@ -224,13 +224,15 @@ func TestUnion(t *testing.T) {
 	result1 := Union([]int{0, 1, 2, 3, 4, 5}, []int{0, 2, 10})
 	result2 := Union([]int{0, 1, 2, 3, 4, 5}, []int{6, 7})
 	result3 := Union([]int{0, 1, 2, 3, 4, 5}, []int{})
-	result4 := Union([]int{0, 1, 2}, []int{0, 1, 2})
-	result5 := Union([]int{}, []int{})
+	result4 := Union([]int{0, 1, 2}, []int{0, 1, 2, 3, 3})
+	result5 := Union([]int{0, 1, 2}, []int{0, 1, 2})
+	result6 := Union([]int{}, []int{})
 	is.Equal(result1, []int{0, 1, 2, 3, 4, 5, 10})
 	is.Equal(result2, []int{0, 1, 2, 3, 4, 5, 6, 7})
 	is.Equal(result3, []int{0, 1, 2, 3, 4, 5})
-	is.Equal(result4, []int{0, 1, 2})
-	is.Equal(result5, []int{})
+	is.Equal(result4, []int{0, 1, 2, 3})
+	is.Equal(result5, []int{0, 1, 2})
+	is.Equal(result6, []int{})
 
 	result11 := Union([]int{0, 1, 2, 3, 4, 5}, []int{0, 2, 10}, []int{0, 1, 11})
 	result12 := Union([]int{0, 1, 2, 3, 4, 5}, []int{6, 7}, []int{8, 9})

map.go

@@ -344,8 +344,24 @@ func FilterMapToSlice[K comparable, V any, R any](in map[K]V, iteratee func(key
 }
 
 // FilterKeys transforms a map into a slice based on predicate returns truthy for specific elements.
+// It is a mix of lo.Filter() and lo.Keys().
 // Play: https://go.dev/play/p/OFlKXlPrBAe
-func FilterKeys[K comparable, V any](in map[K]V, predicate func(key K, value V) bool) []V {
+func FilterKeys[K comparable, V any](in map[K]V, predicate func(key K, value V) bool) []K {
+	result := make([]K, 0)
+
+	for k := range in {
+		if predicate(k, in[k]) {
+			result = append(result, k)
+		}
+	}
+
+	return result
+}
+
+// FilterValues transforms a map into a slice based on predicate returns truthy for specific elements.
+// It is a mix of lo.Filter() and lo.Values().
+// Play: https://go.dev/play/p/YVD5r_h-LX-
+func FilterValues[K comparable, V any](in map[K]V, predicate func(key K, value V) bool) []V {
 	result := make([]V, 0)
 
 	for k := range in {

map_example_test.go

@@ -244,3 +244,25 @@ func ExampleFilterMapToSlice() {
 	fmt.Printf("%v", result)
 	// Output: [2_2 4_4]
 }
+
+func ExampleFilterKeys() {
+	kv := map[int]string{1: "foo", 2: "bar", 3: "baz"}
+
+	result := FilterKeys(kv, func(k int, v string) bool {
+		return v == "foo"
+	})
+
+	fmt.Printf("%v", result)
+	// Output: [1]
+}
+
+func ExampleFilterValues() {
+	kv := map[int]string{1: "foo", 2: "bar", 3: "baz"}
+
+	result := FilterValues(kv, func(k int, v string) bool {
+		return v == "foo"
+	})
+
+	fmt.Printf("%v", result)
+	// Output: [foo]
+}

map_test.go

@@ -537,12 +537,29 @@ func TestFilterKeys(t *testing.T) {
 	result1 := FilterKeys(map[int]string{1: "foo", 2: "bar", 3: "baz"}, func(k int, v string) bool {
 		return v == "foo"
 	})
-	is.Equal([]string{"foo"}, result1)
+	is.Equal([]int{1}, result1)
 	is.Len(result1, 1)
 
 	result2 := FilterKeys(map[string]int{"foo": 1, "bar": 2, "baz": 3}, func(k string, v int) bool {
 		return false
 	})
+	is.Equal([]string{}, result2)
+	is.Len(result2, 0)
+}
+
+func TestFilterValues(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	result1 := FilterValues(map[int]string{1: "foo", 2: "bar", 3: "baz"}, func(k int, v string) bool {
+		return v == "foo"
+	})
+	is.Equal([]string{"foo"}, result1)
+	is.Len(result1, 1)
+
+	result2 := FilterValues(map[string]int{"foo": 1, "bar": 2, "baz": 3}, func(k string, v int) bool {
+		return false
+	})
 	is.Equal([]int{}, result2)
 	is.Len(result2, 0)
 }