[Color 4] Update to support the latest specs

lib/src/functions/color.dart

@@ -3,6 +3,7 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:collection';
+import 'dart:math' as math;
 
 import 'package:collection/collection.dart';
 
@@ -423,11 +424,21 @@ final module = BuiltInModule("color", functions: <Callable>[
       (arguments) => SassString(arguments.first.assertColor("color").space.name,
           quotes: false)),
 
-  _function(
-      "to-space",
-      r"$color, $space",
-      (arguments) =>
-          _colorInSpace(arguments[0], arguments[1].assertString("space"))),
+  _function("to-space", r"$color, $space", (arguments) {
+    var converted = _colorInSpace(arguments[0], arguments[1]);
+    // `color.to-space()` never returns missing channels for legacy color
+    // spaces because they're less compatible and users are probably using a
+    // legacy space because they want a highly compatible color.
+    return converted.isLegacy &&
+            (converted.isChannel0Missing ||
+                converted.isChannel1Missing ||
+                converted.isChannel2Missing ||
+                converted.isAlphaMissing) &&
+            converted.space != (arguments[0] as SassColor).space
+        ? SassColor.forSpaceInternal(converted.space, converted.channel0,
+            converted.channel1, converted.channel2, converted.alpha)
+        : converted;
+  }),
 
   _function("is-legacy", r"$color",
       (arguments) => SassBoolean(arguments[0].assertColor("color").isLegacy)),
@@ -459,7 +470,7 @@ final module = BuiltInModule("color", functions: <Callable>[
             ? ColorSpace.srgb
             : space)
         .toGamut()
-        .toSpace(space);
+        .toSpace(color.space);
   }),
 
   _function("channel", r"$color, $channel, $space: null", (arguments) {
@@ -759,7 +770,8 @@ SassColor _changeColor(
               return alphaArg.value;
             }
           }) ??
-          color.alpha);
+          color.alpha,
+      clamp: false);
 }
 
 /// Returns a copy of [color] with its channel values scaled by the values in
@@ -852,10 +864,15 @@ double _adjustChannel(ColorSpace space, ColorChannel channel, double oldValue,
       adjustmentArg = SassNumber(adjustmentArg.value);
   }
 
-  var result = oldValue + _channelFromValue(channel, adjustmentArg)!;
-  return space.isStrictlyBounded && channel is LinearChannel
-      ? fuzzyClamp(result, channel.min, channel.max)
-      : result;
+  var result =
+      oldValue + _channelFromValue(channel, adjustmentArg, clamp: false)!;
+  return switch (channel) {
+    LinearChannel(lowerClamped: true, :var min) when result < min =>
+      oldValue < min ? math.max(oldValue, result) : min,
+    LinearChannel(upperClamped: true, :var max) when result > max =>
+      oldValue > max ? math.min(oldValue, result) : max,
+    _ => result
+  };
 }
 
 /// Given a map of arguments passed to [_updateComponents] for a legacy color,
@@ -1311,24 +1328,28 @@ Value? _parseNumberOrNone(String text) {
 
 /// Creates a [SassColor] for the given [space] from the given channel values,
 /// or throws a [SassScriptException] if the channel values are invalid.
+///
+/// If [clamp] is true, this will clamp any clamped channels.
 SassColor _colorFromChannels(ColorSpace space, SassNumber? channel0,
     SassNumber? channel1, SassNumber? channel2, double? alpha,
-    {bool fromRgbFunction = false}) {
+    {bool clamp = true, bool fromRgbFunction = false}) {
   switch (space) {
     case ColorSpace.hsl:
       if (channel1 != null) _checkPercent(channel1, 'saturation');
       if (channel2 != null) _checkPercent(channel2, 'lightness');
       return SassColor.hsl(
           channel0.andThen((channel0) => _angleValue(channel0, 'hue')),
-          channel1?.value.clamp(0, 100).toDouble(),
-          channel2?.value.clamp(0, 100).toDouble(),
+          _channelFromValue(space.channels[1], _forcePercent(channel1),
+              clamp: clamp),
+          _channelFromValue(space.channels[2], _forcePercent(channel2),
+              clamp: clamp),
           alpha);
 
     case ColorSpace.hwb:
       channel1?.assertUnit('%', 'whiteness');
       channel2?.assertUnit('%', 'blackness');
-      var whiteness = channel1?.value.clamp(0, 100).toDouble();
-      var blackness = channel2?.value.clamp(0, 100).toDouble();
+      var whiteness = channel1?.value.toDouble();
+      var blackness = channel2?.value.toDouble();
 
       if (whiteness != null &&
           blackness != null &&
@@ -1346,44 +1367,48 @@ SassColor _colorFromChannels(ColorSpace space, SassNumber? channel0,
 
     case ColorSpace.rgb:
       return SassColor.rgbInternal(
-          _channelFromValue(space.channels[0], channel0),
-          _channelFromValue(space.channels[1], channel1),
-          _channelFromValue(space.channels[2], channel2),
+          _channelFromValue(space.channels[0], channel0, clamp: clamp),
+          _channelFromValue(space.channels[1], channel1, clamp: clamp),
+          _channelFromValue(space.channels[2], channel2, clamp: clamp),
           alpha,
           fromRgbFunction ? ColorFormat.rgbFunction : null);
 
-    case ColorSpace.lab ||
-          ColorSpace.lch ||
-          ColorSpace.oklab ||
-          ColorSpace.oklch:
-      return SassColor.forSpaceInternal(
-          space,
-          _channelFromValue(space.channels[0], channel0).andThen((lightness) =>
-              fuzzyClamp(
-                  lightness, 0, (space.channels[0] as LinearChannel).max)),
-          _channelFromValue(space.channels[1], channel1),
-          _channelFromValue(space.channels[2], channel2),
-          alpha);
-
     default:
       return SassColor.forSpaceInternal(
           space,
-          _channelFromValue(space.channels[0], channel0),
-          _channelFromValue(space.channels[1], channel1),
-          _channelFromValue(space.channels[2], channel2),
+          _channelFromValue(space.channels[0], channel0, clamp: clamp),
+          _channelFromValue(space.channels[1], channel1, clamp: clamp),
+          _channelFromValue(space.channels[2], channel2, clamp: clamp),
           alpha);
   }
 }
 
+/// Returns [number] with unit `'%'` regardless of its original unit.
+SassNumber? _forcePercent(SassNumber? number) => switch (number) {
+      null => null,
+      SassNumber(numeratorUnits: ['%'], denominatorUnits: []) => number,
+      _ => SassNumber(number.value, '%')
+    };
+
 /// Converts a channel value from a [SassNumber] into a [double] according to
 /// [channel].
-double? _channelFromValue(ColorChannel channel, SassNumber? value) =>
+///
+/// If [clamp] is true, this clamps [value] according to [channel]'s clamping
+/// rules.
+double? _channelFromValue(ColorChannel channel, SassNumber? value,
+        {bool clamp = true}) =>
     value.andThen((value) => switch (channel) {
           LinearChannel(requiresPercent: true) when !value.hasUnit('%') =>
             throw SassScriptException(
                 'Expected $value to have unit "%".', channel.name),
-          LinearChannel() =>
+          LinearChannel(lowerClamped: false, upperClamped: false) =>
+            _percentageOrUnitless(value, channel.max, channel.name),
+          LinearChannel() when !clamp =>
             _percentageOrUnitless(value, channel.max, channel.name),
+          LinearChannel(:var lowerClamped, :var upperClamped) =>
+            _percentageOrUnitless(value, channel.max, channel.name).clamp(
+                lowerClamped ? channel.min : double.negativeInfinity,
+                upperClamped ? channel.max : double.infinity),
           _ => value.coerceValueToUnit('deg', channel.name) % 360
         });
 

lib/src/util/number.dart

@@ -93,6 +93,11 @@ double fuzzyClamp(double number, double min, double max) {
   return number;
 }
 
+/// Returns whether [number] is within [min] and [max] inclusive, using fuzzy
+/// equality.
+bool fuzzyInRange(double number, num min, num max) =>
+    fuzzyGreaterThanOrEquals(number, min) && fuzzyLessThanOrEquals(number, max);
+
 /// Returns [number] if it's within [min] and [max], or `null` if it's not.
 ///
 /// If [number] is [fuzzyEquals] to [min] or [max], it's clamped to the