e2e: add multiversion flag to generator (tendermint#9829)

* add multiversion flag to generator

* clarify flag comment

test/e2e/generator/generate.go

@@ -22,7 +22,9 @@ var (
 		},
 		"validators": {"genesis", "initchain"},
 	}
-
+	nodeVersions = weightedChoice{
+		"": 2,
+	}
 	// The following specify randomly chosen values for testnet nodes.
 	nodeDatabases = uniformChoice{"goleveldb", "cleveldb", "rocksdb", "boltdb", "badgerdb"}
 	ipv6          = uniformChoice{false, true}
@@ -50,7 +52,10 @@ var (
 )
 
 // Generate generates random testnets using the given RNG.
-func Generate(r *rand.Rand) ([]e2e.Manifest, error) {
+func Generate(r *rand.Rand, multiversion string) ([]e2e.Manifest, error) {
+	if multiversion != "" {
+		nodeVersions[multiversion] = 1
+	}
 	manifests := []e2e.Manifest{}
 	for _, opt := range combinations(testnetCombinations) {
 		manifest, err := generateTestnet(r, opt)
@@ -224,6 +229,7 @@ func generateNode(
 	r *rand.Rand, mode e2e.Mode, syncApp bool, startAt int64, initialHeight int64, forceArchive bool,
 ) *e2e.ManifestNode {
 	node := e2e.ManifestNode{
+		Version:          nodeVersions.Choose(r).(string),
 		Mode:             string(mode),
 		SyncApp:          syncApp,
 		StartAt:          startAt,

test/e2e/generator/main.go

@@ -44,25 +44,31 @@ func NewCLI() *CLI {
 			if err != nil {
 				return err
 			}
-			return cli.generate(dir, groups)
+			multiversion, err := cmd.Flags().GetString("multi-version")
+			if err != nil {
+				return err
+			}
+			return cli.generate(dir, groups, multiversion)
 		},
 	}
 
 	cli.root.PersistentFlags().StringP("dir", "d", "", "Output directory for manifests")
 	_ = cli.root.MarkPersistentFlagRequired("dir")
+	cli.root.PersistentFlags().StringP("multi-version", "m", "", "Include multi-version testing."+
+		"If multi-version is not specified, then only the current Tendermint version will be used in generated testnets.")
 	cli.root.PersistentFlags().IntP("groups", "g", 0, "Number of groups")
 
 	return cli
 }
 
 // generate generates manifests in a directory.
-func (cli *CLI) generate(dir string, groups int) error {
+func (cli *CLI) generate(dir string, groups int, multiversion string) error {
 	err := os.MkdirAll(dir, 0o755)
 	if err != nil {
 		return err
 	}
 
-	manifests, err := Generate(rand.New(rand.NewSource(randomSeed))) //nolint:gosec
+	manifests, err := Generate(rand.New(rand.NewSource(randomSeed)), multiversion) //nolint:gosec
 	if err != nil {
 		return err
 	}

test/e2e/generator/random.go

@@ -83,3 +83,25 @@ func (usc uniformSetChoice) Choose(r *rand.Rand) []string {
 	}
 	return choices
 }
+
+// weightedChoice chooses a single random key from a map of keys and weights.
+type weightedChoice map[interface{}]uint
+
+func (wc weightedChoice) Choose(r *rand.Rand) interface{} {
+	total := 0
+	choices := make([]interface{}, 0, len(wc))
+	for choice, weight := range wc {
+		total += int(weight)
+		choices = append(choices, choice)
+	}
+
+	rem := r.Intn(total)
+	for _, choice := range choices {
+		rem -= int(wc[choice])
+		if rem <= 0 {
+			return choice
+		}
+	}
+
+	return nil
+}