Not that it should be relevant, but this was running under testing/synctest as well... go version go1.25rc2 darwin/amd64
On Saturday, August 9, 2025 at 11:45:55 PM UTC+1 Jason E. Aten wrote: > I'm trying to use generics to display a map contents, sorted by key. > > It is not going well. > > Here is the (minimized/extracted) code I am using: > > https://go.dev/play/p/_GpoXKp9kER > > I'm staring at the following crash dump from a red test. Notice the > node list is not sorted, but random: (the project is a distributed > system that maintains a cluster membership list; here a test for removing > a node from the cluster is failing...) > > *panic: expected 'node_7' to be gone! membership after > SingleUpdateClusterMemberConfig; memlistAfterRemove = 'memMap of len(8):* > > * node_6* > > * node_5* > > * node_1* > > * node_0* > > * node_4* > > * node_3* > > * node_7* > > * node_2* > > * '; nodes[7].PeerID = 'oXs3x5peQ2EOt1esGrOM0axFQO2x'* > > However, the string that generated that list *TRIED TO SORT IT*. That > code looks like this: > > * _, present := memlistAfterRemove[nodes[i].PeerID]* > > * if present {* > > * panic(fmt.Sprintf("expected '%v' to be gone! membership after > SingleUpdateClusterMemberConfig; memlistAfterRemove = '%v'; > nodes[%v].PeerID = '%v'", namei, memlistAfterRemove, i, nodes[i].PeerID))* > > * }* > > *and the sorting code is exactly the String() code shown in the playgound > link above ( *https://go.dev/play/p/_GpoXKp9kER ) > > *The mystery is: why didn't the node list come out sorted?* > > Any thoughts? > > Thanks! > > - Jason > > code in case playground not available: > > > package main > > import ( > "cmp" > "fmt" > "iter" > "slices" > ) > > // sort any map by its keys > func sorted[K cmp.Ordered, V any](m map[K]V) iter.Seq2[K, V] { > > return func(yield func(K, V) bool) { > > var keys []K > for k := range m { > keys = append(keys, k) > } > slices.Sort(keys) > for _, k := range keys { > v := m[k] > if !yield(k, v) { > return > } > } > } // end seq2 definition > } > > type memMap map[string]string > > func (m memMap) String() (r string) { > r = fmt.Sprintf("memMap of len(%v):\n", len(m)) > for key := range sorted(m) { > r += fmt.Sprintf(" %v\n", key) > } > return > } > > func main() { > m := make(memMap) > m["node_2"] = "2" > m["node_1"] = "1" > m["node_0"] = "0" > m["node_9"] = "9" > > fmt.Printf("%v\n", m) > fmt.Printf("%v\n", m) > fmt.Printf("%v\n", m) > } > > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/018943fb-06b5-4878-95a6-d707344aced6n%40googlegroups.com.
