go/loader: normalize cycle to remove flake
Fixes golang/go#31279
Change-Id: Idd1eead3b1e9a90ba39d04019ef32200deb4c983
Reviewed-on: https://go-review.googlesource.com/c/tools/+/185984
Run-TryBot: Michael Matloob <matloob@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
diff --git a/go/loader/loader.go b/go/loader/loader.go
index de34b80..bc12ca3 100644
--- a/go/loader/loader.go
+++ b/go/loader/loader.go
@@ -811,7 +811,15 @@
// Import of incomplete package: this indicates a cycle.
fromPath := from.Pkg.Path()
if cycle := imp.findPath(path, fromPath); cycle != nil {
- cycle = append([]string{fromPath}, cycle...)
+ // Normalize cycle: start from alphabetically largest node.
+ pos, start := -1, ""
+ for i, s := range cycle {
+ if pos < 0 || s > start {
+ pos, start = i, s
+ }
+ }
+ cycle = append(cycle, cycle[:pos]...)[pos:] // rotate cycle to start from largest
+ cycle = append(cycle, cycle[0]) // add start node to end to show cycliness
return nil, fmt.Errorf("import cycle: %s", strings.Join(cycle, " -> "))
}
