Fix CheckPostalCode to Validate Input Strictly (#3)

* Fix CheckPostalCode to only pass valid inputs

* Reject non-empty postal codes if not required

Author: evnaz

address.go

@@ -83,13 +83,18 @@ func (f Format) CheckRegion(region string) bool {
 //
 // An empty postal code is considered valid.
 func (f Format) CheckPostalCode(postalCode string) bool {
-	if postalCode == "" || f.PostalCodePattern == "" {
+	if postalCode == "" {
 		return true
 	}
-	rx := regexp.MustCompile(f.PostalCodePattern)
+	rx := regexp.MustCompile(f.PostalCodeValidationPattern())
 	return rx.MatchString(postalCode)
 }
 
+// PostalCodeValidationPattern returns the full regex pattern for validating the postal code.
+func (f *Format) PostalCodeValidationPattern() string {
+	return "^" + f.PostalCodePattern + "$"
+}
+
 // SelectLayout selects the correct layout for the given locale.
 func (f Format) SelectLayout(locale Locale) string {
 	if f.LocalLayout != "" && f.useLocalData(locale) {

address_test.go

@@ -108,9 +108,13 @@ func TestFormat_CheckPostalCode(t *testing.T) {
 		// Valid postal code.
 		{"FR", "75002", true},
 		// Invalid postal code.
-		{"FR", "INVALID", false},
+		{"FR", "A75002", false},
+		// Invalid postal code.
+		{"FR", "75002B", false},
+		// Country with no predefined pattern.
+		{"AG", "AG123", false},
 		// Country with no predefined pattern.
-		{"AG", "AG123", true},
+		{"AG", "", true},
 	}
 
 	for _, tt := range tests {