fix: align-self not work for positioned flex item

integration_tests/specs/css/css-flexbox/align-self.ts

@@ -1695,4 +1695,105 @@ describe('align-self', () => {
       done();
     });
   });
+
+  it('stretch should not work with positioned child of no top bottom', async () => {
+    let item = createElement('div', {
+        style: {
+            display: 'flex',
+            flexDirection: 'row',
+            height: '50px',
+            backgroundColor: 'coral',
+        }
+    }, [
+        createElement('div', {
+            style: {
+                position: 'absolute',
+                alignSelf: 'stretch',
+                backgroundColor: 'lightblue',
+            }
+        }, [
+            createText('stretch')
+        ]),
+    ]);
+
+    BODY.appendChild(item);
+
+    await snapshot();
+  });
+
+  it('flex-start should work with positioned child of no top bottom', async () => {
+    let item = createElement('div', {
+        style: {
+            display: 'flex',
+            flexDirection: 'row',
+            alignItems: 'center',
+            height: '50px',
+            backgroundColor: 'coral',
+        }
+    }, [
+        createElement('div', {
+            style: {
+                position: 'absolute',
+                alignSelf: 'flex-start',
+                backgroundColor: 'lightblue',
+            }
+        }, [
+            createText('flex-start')
+        ]),
+    ]);
+
+    BODY.appendChild(item);
+
+    await snapshot();
+  });
+
+  it('center should work with positioned child of no top bottom', async () => {
+    let item = createElement('div', {
+        style: {
+            display: 'flex',
+            flexDirection: 'row',
+            height: '50px',
+            backgroundColor: 'coral',
+        }
+    }, [
+        createElement('div', {
+            style: {
+                position: 'absolute',
+                alignSelf: 'center',
+                backgroundColor: 'lightblue',
+            }
+        }, [
+            createText('center')
+        ]),
+    ]);
+
+    BODY.appendChild(item);
+
+    await snapshot();
+  });
+
+  it('flex-end should work with positioned child of no top bottom', async () => {
+    let item = createElement('div', {
+        style: {
+            display: 'flex',
+            flexDirection: 'row',
+            height: '50px',
+            backgroundColor: 'coral',
+        }
+    }, [
+        createElement('div', {
+            style: {
+                position: 'absolute',
+                alignSelf: 'flex-end',
+                backgroundColor: 'lightblue',
+            }
+        }, [
+            createText('flex-end')
+        ]),
+    ]);
+
+    BODY.appendChild(item);
+
+    await snapshot();
+  });
 });

kraken/lib/src/css/render_style.dart

@@ -833,6 +833,15 @@ class CSSRenderStyle
     bool isFlexNoWrap = false;
     bool isChildStretchSelf = false;
     if (isParentFlex) {
+      // The absolutely-positioned box is considered to be “fixed-size”, a value of stretch
+      // is treated the same as flex-start.
+      // https://www.w3.org/TR/css-flexbox-1/#abspos-items
+      bool isPositioned = renderStyle.position == CSSPositionType.absolute
+        || renderStyle.position == CSSPositionType.fixed;
+      if (isPositioned) {
+        return false;
+      }
+
       isHorizontalDirection = CSSFlex.isHorizontalFlexDirection(parentRenderStyle.flexDirection);
       isFlexNoWrap = parentRenderStyle.flexWrap != FlexWrap.wrap &&
         parentRenderStyle.flexWrap != FlexWrap.wrapReverse;

kraken/lib/src/rendering/flex.dart

@@ -291,13 +291,16 @@ class RenderFlexLayout extends RenderLayoutBox {
   }
 
   AlignSelf _getAlignSelf(RenderBox child) {
-    // Flex shrink has no effect on placeholder of positioned element.
-    if (child is RenderPositionPlaceholder) {
-      return AlignSelf.auto;
+    RenderBoxModel? childRenderBoxModel;
+    if (child is RenderBoxModel) {
+      childRenderBoxModel = child;
+    } else if (child is RenderPositionPlaceholder) {
+      childRenderBoxModel = child.positioned;
+    }
+    if (childRenderBoxModel != null) {
+      return childRenderBoxModel.renderStyle.alignSelf;
     }
-    return child is RenderBoxModel
-        ? child.renderStyle.alignSelf
-        : AlignSelf.auto;
+    return AlignSelf.auto;
   }
 
   double _getMaxMainAxisSize(RenderBox child) {
@@ -1992,6 +1995,14 @@ class RenderFlexLayout extends RenderLayoutBox {
     // Position placeholder and BR element has size of zero, so they can not be stretched.
     if (child is RenderPositionPlaceholder || child is RenderLineBreak) return false;
 
+    // The absolutely-positioned box is considered to be “fixed-size”, a value of stretch
+    // is treated the same as flex-start.
+    // https://www.w3.org/TR/css-flexbox-1/#abspos-items
+    final RenderLayoutParentData childParentData = child.parentData as RenderLayoutParentData;
+    if (child is RenderBoxModel && childParentData.isPositioned) {
+      return false;
+    }
+
     AlignSelf alignSelf = _getAlignSelf(child);
     bool isChildAlignmentStretch = alignSelf != AlignSelf.auto
       ? alignSelf == AlignSelf.stretch