fix(size): move byte sizes to the next unit when rounding reaches 1024

internal/frontend/cli/upgrade.go

@@ -775,7 +775,9 @@ func humanSize(b int64) string {
 		_MiB = 1024 * _KiB
 	)
 	switch {
-	case b >= _MiB:
+	// From _MiB-51 bytes up, the KiB figure rounds to "1024.0" at one decimal
+	// place, so show it as MiB instead.
+	case b >= _MiB-51:
 		return fmt.Sprintf("%.1f MiB", float64(b)/float64(_MiB))
 	case b >= _KiB:
 		return fmt.Sprintf("%.1f KiB", float64(b)/float64(_KiB))

internal/frontend/cli/upgrade_test.go

@@ -206,6 +206,12 @@ func TestHumanSize(t *testing.T) {
 		{500, "500 B"},
 		{2048, "2.0 KiB"},
 		{19_000_000, "18.1 MiB"},
+		// Sizes just under the next unit round up to it: show "1.0 MiB",
+		// never "1024.0 KiB".
+		{1_048_524, "1023.9 KiB"},
+		{1_048_525, "1.0 MiB"},
+		{1_048_575, "1.0 MiB"},
+		{1_023, "1023 B"},
 	}
 	for _, tt := range tests {
 		if got := humanSize(tt.bytes); got != tt.want {

internal/tools/builtin/bgjobs.go

@@ -339,7 +339,9 @@ func stillRunning(p *jobs.Progress) string {
 
 func byteCount(n int64) string {
 	switch {
-	case n >= 1<<20:
+	// From 1<<20 - 51 bytes up, the KB figure rounds to "1024.0" at one
+	// decimal place, so show it as MB instead.
+	case n >= 1<<20-51:
 		return fmt.Sprintf("%.1f MB", float64(n)/(1<<20))
 	case n >= 1<<10:
 		return fmt.Sprintf("%.1f KB", float64(n)/(1<<10))

internal/tools/builtin/bgjobs_bytecount_test.go

@@ -0,0 +1,22 @@
+package builtin
+
+import "testing"
+
+func TestByteCountMovesToNextUnitWhenRoundingReachesIt(t *testing.T) {
+	tests := []struct {
+		n    int64
+		want string
+	}{
+		{1023, "1023 B"},
+		{1024, "1.0 KB"},
+		{1_048_524, "1023.9 KB"},
+		{1_048_525, "1.0 MB"},
+		{1_048_575, "1.0 MB"},
+		{1 << 20, "1.0 MB"},
+	}
+	for _, tt := range tests {
+		if got := byteCount(tt.n); got != tt.want {
+			t.Errorf("byteCount(%d) = %q, want %q", tt.n, got, tt.want)
+		}
+	}
+}