Map every byte the router's id refuses in an ask id, so a group with = gives a usable ask (issue 1201)

go/delivery/gate.go

@@ -94,18 +94,30 @@ func ParseAskKey(key string) (kind, group, hash string, err error) {
 func AnswerKey(askKey string) string { return askKey }
 
 // AskID is the id the teller gives the router for the ask at askKey. The router's ids refuse dots (asks.UsableID),
-// so in the readable part a dot becomes `-` and a slash `_`; that part is cut to fit, and every id ends in `-` and
+// so in the readable part a dot becomes `-` and any other byte outside letters, digits, `_` and `-` becomes `_`; that part is cut to fit, and every id ends in `-` and
 // the first 12 hex digits of the sha256 of the whole key, so two keys never give one id. It cannot be read back:
 // the teller keeps the key beside it.
 func AskID(askKey string) string {
 	const most = 64 // the router's bound on an id
 	const tail = 13 // "-" and 12 hex digits
-	readable := strings.NewReplacer(".", "-", "/", "_").Replace(askKey)
+	readable := []byte(askKey)
+	for i, c := range readable {
+		switch {
+		case c >= 'A' && c <= 'Z', c >= 'a' && c <= 'z', c >= '0' && c <= '9':
+		case c == '.':
+			readable[i] = '-'
+		default: // a slash, an equals sign or any other byte the router's id refuses
+			readable[i] = '_'
+		}
+	}
+	if len(readable) > 0 && (readable[0] == '-' || readable[0] == '_') {
+		readable[0] = 'k' // an id starts with a letter or digit
+	}
 	if len(readable) > most-tail {
 		readable = readable[:most-tail]
 	}
 	sum := sha256.Sum256([]byte(askKey))
-	return readable + "-" + hex.EncodeToString(sum[:])[:12]
+	return string(readable) + "-" + hex.EncodeToString(sum[:])[:12]
 }
 
 func checkOwedAct(act string) (kind, context string, err error) {

go/delivery/gate_test.go

@@ -57,8 +57,10 @@ func TestAskID(t *testing.T) { // 1201/AC2
 	long2, _ := MergeAskKey("feat/"+strings.Repeat("long-", 20)+"2", gateHeads())
 	slash, _ := MergeAskKey("a/b", gateHeads())
 	under, _ := MergeAskKey("a_b", gateHeads())
+	eq, _ := MergeAskKey("feat=x", gateHeads())
+	eqs, _ := MergeAskKey("feat_x", gateHeads())
 	seen := map[string]string{}
-	for _, k := range []string{k1, k2, k3, long, long2, slash, under} {
+	for _, k := range []string{k1, k2, k3, long, long2, slash, under, eq, eqs, "=odd.key"} {
 		id := AskID(k)
 		if strings.Contains(id, ".") {
 			t.Errorf("id %q holds a dot", id)