Uses the sum of border and padding if it's greater than the container definite size

src/compute/flexbox.rs

@@ -1,4 +1,6 @@
 //! Computes the [flexbox](https://css-tricks.com/snippets/css/a-guide-to-flexbox/) layout algorithm on [`TaffyTree`](crate::TaffyTree) according to the [spec](https://www.w3.org/TR/css-flexbox-1/)
+use core::ops::Add;
+
 use crate::compute::common::alignment::compute_alignment_offset;
 use crate::geometry::{Line, Point, Rect, Size};
 use crate::style::{
@@ -171,7 +173,17 @@ pub fn compute_flexbox_layout(tree: &mut impl LayoutPartialTree, node: NodeId, i
         (Some(min), Some(max)) if max <= min => Some(min),
         _ => None,
     });
-    let styled_based_known_dimensions = known_dimensions.or(min_max_definite_size).or(clamped_style_size);
+
+    // if the sum of the padding and border is greater than the size of the container, the
+    // the result overwrites the size of the container
+    let padding_border_sum = style
+        .padding
+        .resolve_or_zero(parent_size.width)
+        .sum_axes()
+        .add(style.border.resolve_or_zero(parent_size.width).sum_axes());
+
+    let styled_based_known_dimensions =
+        known_dimensions.or(min_max_definite_size).or(clamped_style_size).maybe_max(padding_border_sum);
 
     // Short-circuit layout if the container's size is fully determined by the container's size and the run mode
     // is ComputeSize (and thus the container's size is all that we're interested in)
@@ -2167,9 +2179,10 @@ mod tests {
 
     use crate::{
         geometry::Size,
+        prelude::{length, TaffyMaxContent},
         style::{FlexWrap, Style},
         util::{MaybeMath, ResolveOrZero},
-        TaffyTree,
+        Rect, TaffyTree,
     };
 
     // Make sure we get correct constants
@@ -2208,4 +2221,31 @@ mod tests {
         assert_eq!(constants.container_size, Size::zero());
         assert_eq!(constants.inner_container_size, Size::zero());
     }
+
+    #[test]
+    pub fn test_padding_and_border_larger_than_definite_size() {
+        let mut tree: TaffyTree<()> = TaffyTree::with_capacity(16);
+
+        let child = tree.new_leaf(Style::default()).unwrap();
+
+        let root = tree
+            .new_with_children(
+                Style {
+                    size: Size { width: length(10.0), height: length(10.0) },
+                    padding: Rect { left: length(10.0), right: length(10.0), top: length(10.0), bottom: length(10.0) },
+
+                    border: Rect { left: length(10.0), right: length(10.0), top: length(10.0), bottom: length(10.0) },
+                    ..Default::default()
+                },
+                &[child],
+            )
+            .unwrap();
+
+        tree.compute_layout(root, Size::MAX_CONTENT).unwrap();
+
+        let layout = tree.layout(root).unwrap();
+
+        assert_eq!(layout.size.width, 40.0);
+        assert_eq!(layout.size.height, 40.0);
+    }
 }