adjust validation function

Author: jsonbailey

pkgs/sdk/server/src/ConfigurationBuilder.cs

@@ -59,7 +59,7 @@ public sealed class ConfigurationBuilder
         /// </summary>
         private void SetSdkKeyIfValid(string sdkKey)
         {
-            if (ValidationUtils.ValidateSdkKeyFormat(sdkKey) == null)
+            if (ValidationUtils.IsValidSdkKeyFormat(sdkKey))
             {
                 _sdkKey = sdkKey;
             }

pkgs/shared/common/src/Helpers/ValidationUtils.cs

@@ -9,36 +9,39 @@ namespace LaunchDarkly.Sdk.Helpers
     public static class ValidationUtils
     {
         private static readonly Regex ValidCharsRegex = new Regex("^[-a-zA-Z0-9._]+\\z");
+        private const int MaxSdkKeyLength = 8192;
 
         /// <summary>
-        /// Validates that a string does not contain invalid characters or exceed the max length of 8192 characters.
+        /// Validates that a string does not contain invalid characters and is not too long for our systems.
         /// </summary>
         /// <param name="sdkKey">the SDK key to validate.</param>
         /// <returns>Null if the input is valid, otherwise an error string describing the issue.</returns>
-        public static string ValidateSdkKeyFormat(string sdkKey)
+        public static bool IsValidSdkKeyFormat(string sdkKey, out string errorMessage)
         {
 
             // For offline mode, we allow a null or empty SDK key and it is not invalid.
             if (string.IsNullOrEmpty(sdkKey))
             {
-                return null;
+                return true;
             }
 
-            if (sdkKey.Length > 8192)
+            if (sdkKey.Length > MaxSdkKeyLength)
             {
-                return "SDK key cannot be longer than 1024 characters.";
+                errorMessage = $"SDK key cannot be longer than {MaxSdkKeyLength} characters.";
+                return false;
             }
 
             if (!ValidCharsRegex.IsMatch(sdkKey))
             {
-                return "SDK key contains invalid characters.";
+                errorMessage = "SDK key contains invalid characters.";
+                return false;
             }
 
-            return null;
+            return true;
         }
 
         /// <summary>
-        /// Validates that a string is non-empty, not too longer for our systems, and only contains
+        /// Validates that a string is non-empty, not too long for our systems, and only contains
         /// alphanumeric characters, hyphens, periods, and underscores.
         /// </summary>
         /// <param name="s">the string to validate.</param>