feat: enhance community attribute handling in BIRD format. Add validation for community route bodies to ensure correct tuple structure and introduce tests for single-element standard arrays, improving error handling and robustness in community attribute processing.

internal/birdfmt/community_bird.go

@@ -10,6 +10,10 @@ import (
 
 var standardPairRE = regexp.MustCompile(`^\s*(\d{1,5}):(\d{1,5})\s*$`)
 
+// badCommunityAddRE matches invalid BIRD filter calls like bgp_community.add(65000,1)
+// (first argument is an int). Valid form is bgp_community.add((65000,1)); — note the pair tuple.
+var badCommunityAddRE = regexp.MustCompile(`\b(?:bgp_community|bgp_large_community)\.add\(\s*\d`)
+
 // RouteCommunityAttrs returns BIRD 2 lines (indented with 4 spaces) for use inside a static `route … { … }` block.
 // Empty string means no community attributes.
 func RouteCommunityAttrs(kind, name, valueJSON string) (string, error) {
@@ -20,26 +24,46 @@ func RouteCommunityAttrs(kind, name, valueJSON string) (string, error) {
 	}
 
 	if s, ok := parseLargeFromJSONLoose(raw); ok {
+		if err := validateCommunityRouteBody(s); err != nil {
+			return "", err
+		}
 		return s, nil
 	}
 	_ = kind // reserved for future kinds (e.g. extended communities)
 
 	if m := standardPairRE.FindStringSubmatch(name); len(m) == 3 {
-		return standardAddLine(m[1], m[2])
+		s, err := standardAddLine(m[1], m[2])
+		if err != nil {
+			return "", err
+		}
+		return s, validateCommunityRouteBody(s)
 	}
 
 	var obj map[string]any
 	if json.Unmarshal([]byte(raw), &obj) == nil {
 		if v, ok := obj["standard"].(string); ok {
 			if m := standardPairRE.FindStringSubmatch(v); len(m) == 3 {
-				return standardAddLine(m[1], m[2])
+				s, err := standardAddLine(m[1], m[2])
+				if err != nil {
+					return "", err
+				}
+				return s, validateCommunityRouteBody(s)
 			}
 		}
-		if arr, ok := obj["standard"].([]any); ok && len(arr) == 2 {
-			a, aok := numberToUint32String(arr[0])
-			b, bok := numberToUint32String(arr[1])
-			if aok && bok {
-				return standardAddLine(a, b)
+		if arr, ok := obj["standard"].([]any); ok {
+			if len(arr) == 1 {
+				return "", fmt.Errorf(`birdfmt: value_json "standard" must be a pair [a,b] or "a:b" string, got single element`)
+			}
+			if len(arr) == 2 {
+				a, aok := numberToUint32String(arr[0])
+				b, bok := numberToUint32String(arr[1])
+				if aok && bok {
+					s, err := standardAddLine(a, b)
+					if err != nil {
+						return "", err
+					}
+					return s, validateCommunityRouteBody(s)
+				}
 			}
 		}
 	}
@@ -47,13 +71,36 @@ func RouteCommunityAttrs(kind, name, valueJSON string) (string, error) {
 	var strVal string
 	if json.Unmarshal([]byte(raw), &strVal) == nil {
 		if m := standardPairRE.FindStringSubmatch(strVal); len(m) == 3 {
-			return standardAddLine(m[1], m[2])
+			s, err := standardAddLine(m[1], m[2])
+			if err != nil {
+				return "", err
+			}
+			return s, validateCommunityRouteBody(s)
 		}
 	}
 
 	return "", nil
 }
 
+// validateCommunityRouteBody rejects lines that would make BIRD 2 fail parse-check with
+// "Argument 1 of 'add' expected clist / quad / ip / pair, got int" (wrong add() shape).
+func validateCommunityRouteBody(body string) error {
+	body = strings.TrimSpace(body)
+	if body == "" {
+		return nil
+	}
+	for _, line := range strings.Split(body, "\n") {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		if badCommunityAddRE.MatchString(line) {
+			return fmt.Errorf("birdfmt: invalid community line (expected pair/triple tuple inside add(), e.g. bgp_community.add((65000,1));): %q", line)
+		}
+	}
+	return nil
+}
+
 func standardAddLine(a, b string) (string, error) {
 	ai, err1 := strconv.ParseUint(strings.TrimSpace(a), 10, 16)
 	bi, err2 := strconv.ParseUint(strings.TrimSpace(b), 10, 16)
@@ -111,6 +158,11 @@ func numberToUint32String(v any) (string, bool) {
 			return "", false
 		}
 		return strconv.FormatUint(uint64(x), 10), true
+	case int64:
+		if x < 0 || x > 4294967295 {
+			return "", false
+		}
+		return strconv.FormatUint(uint64(x), 10), true
 	case string:
 		n, err := strconv.ParseUint(strings.TrimSpace(x), 10, 32)
 		if err != nil {

internal/birdfmt/community_bird_test.go

@@ -21,3 +21,10 @@ func TestRouteCommunityAttrs_LargeJSON(t *testing.T) {
 		t.Fatalf("got %q", s)
 	}
 }
+
+func TestRouteCommunityAttrs_StandardArrayOneElement(t *testing.T) {
+	_, err := RouteCommunityAttrs("", "x", `{"standard":[65000]}`)
+	if err == nil {
+		t.Fatal("expected error for single-element standard pair")
+	}
+}