dashboard/app: aggregate coverage drop numbers bottom-up

Tree view now shows the total drop for every item.

2 files changed, 12 insertions, 1 deletions

diff --git a/pkg/cover/heatmap.go b/pkg/cover/heatmap.go
index bdb79eec4..751b53ea6 100644
--- a/pkg/cover/heatmap.go
+++ b/pkg/cover/heatmap.go
@@ -279,7 +279,16 @@ func FormatResult(thm *templateHeatmap, format Format) {
 		})
 		// We want to show the coverage drop numbers instead of total instrumented blocks.
 		thm.Transform(func(row *templateHeatmapRow) {
-			row.Summary = -1 * (slices.Max(row.Covered) - row.Covered[len(row.Covered)-1])
+			if !row.IsDir {
+				row.Summary = -1 * (slices.Max(row.Covered) - row.Covered[len(row.Covered)-1])
+				return
+			}
+			row.Summary = 0
+			for _, item := range row.Items {
+				if item.Summary < 0 { // only the items with coverage drop
+					row.Summary += item.Summary
+				}
+			}
 		})
 	}
 }
diff --git a/pkg/cover/heatmap_test.go b/pkg/cover/heatmap_test.go
index 41e643cf2..1c094f1dd 100644
--- a/pkg/cover/heatmap_test.go
+++ b/pkg/cover/heatmap_test.go
@@ -305,10 +305,12 @@ func TestFormatResult(t *testing.T) {
 							Name:    "dir",
 							Covered: []int64{1, 1},
 							IsDir:   true,
+							Summary: -15,
 						},
 					},
 					Covered: []int64{1, 1},
 					IsDir:   true,
+					Summary: -15,
 				},
 			},
 		},