From af21d9f5b360dee1343386bcc02f6ff5bd6d48fa Mon Sep 17 00:00:00 2001
From: gaaclarke <30870216+gaaclarke@users.noreply.github.com>
Date: Mon, 16 Sep 2024 14:20:32 -0700
Subject: [PATCH] Added .keys to ColorSwatch (#155262)

This addresses the issue that ColorSwatch has operator[], but no way to know what are valid inputs.

issue: https://github.com/flutter/flutter/issues/155113
---
 packages/flutter/lib/src/painting/colors.dart   | 9 ++++++---
 packages/flutter/test/painting/colors_test.dart | 1 +
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/packages/flutter/lib/src/painting/colors.dart b/packages/flutter/lib/src/painting/colors.dart
index 5a306590a3c..a897c0b33d6 100644
--- a/packages/flutter/lib/src/painting/colors.dart
+++ b/packages/flutter/lib/src/painting/colors.dart
@@ -398,7 +398,7 @@ class HSLColor {
 
 /// A color that has a small table of related colors called a "swatch".
 ///
-/// The table is indexed by values of type `T`.
+/// The table is accessed by key values of type `T`.
 ///
 /// See also:
 ///
@@ -413,14 +413,17 @@ class ColorSwatch<T> extends Color {
   /// The `primary` argument should be the 32 bit ARGB value of one of the
   /// values in the swatch, as would be passed to the [Color.new] constructor
   /// for that same color, and as is exposed by [value]. (This is distinct from
-  /// the specific index of the color in the swatch.)
+  /// the key of any color in the swatch.)
   const ColorSwatch(super.primary, this._swatch);
 
   @protected
   final Map<T, Color> _swatch;
 
   /// Returns an element of the swatch table.
-  Color? operator [](T index) => _swatch[index];
+  Color? operator [](T key) => _swatch[key];
+
+  /// Returns the valid keys for accessing operator[].
+  Iterable<T> get keys => _swatch.keys;
 
   @override
   bool operator ==(Object other) {
diff --git a/packages/flutter/test/painting/colors_test.dart b/packages/flutter/test/painting/colors_test.dart
index 470601d0caf..97917619341 100644
--- a/packages/flutter/test/painting/colors_test.dart
+++ b/packages/flutter/test/painting/colors_test.dart
@@ -436,6 +436,7 @@ void main() {
     expect(greens1.hashCode, greens2.hashCode);
     expect(greens1['2259 C'], const Color(0xFF027223));
     expect(greens1.value, 0xFF027223);
+    expect(listEquals(greens1.keys.toList(), greens2.keys.toList()), isTrue);
   });
 
   test('ColorSwatch.lerp', () {