Fix wrap compute max intrinsic width/height with spacing (#82609)

packages/flutter/lib/src/rendering/wrap.dart

@@ -421,7 +421,7 @@ class RenderWrap extends RenderBox
   double computeMaxIntrinsicWidth(double height) {
     switch (direction) {
       case Axis.horizontal:
-        double width = 0.0;
+        double width = math.max(childCount - 1, 0) * spacing;
         RenderBox? child = firstChild;
         while (child != null) {
           width += child.getMaxIntrinsicWidth(double.infinity);
@@ -455,7 +455,7 @@ class RenderWrap extends RenderBox
       case Axis.horizontal:
         return computeDryLayout(BoxConstraints(maxWidth: width)).height;
       case Axis.vertical:
-        double height = 0.0;
+        double height = math.max(childCount - 1, 0) * spacing;
         RenderBox? child = firstChild;
         while (child != null) {
           height += child.getMaxIntrinsicHeight(double.infinity);

packages/flutter/test/rendering/wrap_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:math' as math;
+
 import 'package:flutter/rendering.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -219,4 +221,91 @@ void main() {
       expect(context.clipBehavior, equals(clip));
     }
   });
+
+  test('Compute max intrinsic height with spacing', () {
+    const double itemWidth = 64;
+    const double itemHeight = 32;
+
+    final RenderBox child = RenderConstrainedBox(
+      additionalConstraints: const BoxConstraints.tightFor(
+        width: itemWidth,
+        height: itemHeight,
+      ),
+    );
+
+    final RenderWrap renderWrap = RenderWrap();
+    renderWrap.add(child);
+
+    renderWrap.spacing = 5;
+    renderWrap.direction = Axis.vertical;
+
+    expect(renderWrap.computeMaxIntrinsicHeight(double.infinity), itemHeight);
+
+
+    final List<RenderBox> children = <RenderBox>[
+      RenderConstrainedBox(
+        additionalConstraints: const BoxConstraints.tightFor(
+          width: itemWidth,
+          height: itemHeight,
+        ),
+      ),
+      RenderConstrainedBox(
+        additionalConstraints: const BoxConstraints.tightFor(
+          width: itemWidth,
+          height: itemHeight,
+        ),
+      ),
+    ];
+
+    children.forEach(renderWrap.add);
+
+    final double childrenHeight = renderWrap.childCount * itemHeight;
+    final double spacingHeight = math.max(renderWrap.childCount - 1, 0) * renderWrap.spacing;
+
+    expect(renderWrap.computeMaxIntrinsicHeight(double.infinity), childrenHeight + spacingHeight);
+  });
+
+  test('Compute max intrinsic width with spacing', () {
+    const double itemWidth = 64;
+    const double itemHeight = 32;
+
+    final RenderBox child = RenderConstrainedBox(
+      additionalConstraints: const BoxConstraints.tightFor(
+        width: itemWidth,
+        height: itemHeight,
+      ),
+    );
+
+    final RenderWrap renderWrap = RenderWrap();
+    renderWrap.add(child);
+
+    renderWrap.spacing = 5;
+    renderWrap.direction = Axis.horizontal;
+
+    expect(renderWrap.computeMaxIntrinsicWidth(double.infinity), itemWidth);
+
+
+    final List<RenderBox> children = <RenderBox>[
+      RenderConstrainedBox(
+        additionalConstraints: const BoxConstraints.tightFor(
+          width: itemWidth,
+          height: itemHeight,
+        ),
+      ),
+      RenderConstrainedBox(
+        additionalConstraints: const BoxConstraints.tightFor(
+          width: itemWidth,
+          height: itemHeight,
+        ),
+      ),
+    ];
+
+    children.forEach(renderWrap.add);
+
+    final double childrenWidth = renderWrap.childCount * itemWidth;
+    final double spacingWidth = math.max(renderWrap.childCount - 1, 0) * renderWrap.spacing;
+
+    expect(renderWrap.computeMaxIntrinsicWidth(double.infinity), childrenWidth + spacingWidth);
+  });
+
 }