PrepareScript should work for parameterless scripts; fix #2164 (#2166)

* PrepareScript should work for parameterless scripts; fix #2164 * update link in release notes * tyop
StackExchange · Jun 21, 2022 · bc0c5a2 · bc0c5a2
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diff --git a/docs/ReleaseNotes.md b/docs/ReleaseNotes.md
@@ -1,5 +1,9 @@
 # Release Notes
 
+## Pending
+
+- Fix: [#2164](https://github.com/StackExchange/StackExchange.Redis/issues/2164): fix `LuaScript.Prepare` for scripts that don't have parameters ([#2166 by MarcGravell](https://github.com/StackExchange/StackExchange.Redis/pull/2166))
+
 ## 2.6.45
 
 - Adds: [Nullable reference type](https://docs.microsoft.com/en-us/dotnet/csharp/nullable-references) annotations ([#2041 by NickCraver](https://github.com/StackExchange/StackExchange.Redis/pull/2041))

diff --git a/src/StackExchange.Redis/ScriptParameterMapper.cs b/src/StackExchange.Redis/ScriptParameterMapper.cs
@@ -26,13 +26,12 @@ public ScriptParameters(RedisKey[] keys, RedisValue[] args)
 
         private static readonly Regex ParameterExtractor = new Regex(@"@(?<paramName> ([a-z]|_) ([a-z]|_|\d)*)", RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace);
 
-        private static bool TryExtractParameters(string script, [NotNullWhen(true)] out string[]? parameters)
+        private static string[] ExtractParameters(string script)
         {
             var ps = ParameterExtractor.Matches(script);
             if (ps.Count == 0)
             {
-                parameters = null;
-                return false;
+                return Array.Empty<string>();
             }
 
             var ret = new HashSet<string>();
@@ -56,8 +55,7 @@ private static bool TryExtractParameters(string script, [NotNullWhen(true)] out
                 if (!ret.Contains(n)) ret.Add(n);
             }
 
-            parameters = ret.ToArray();
-            return true;
+            return ret.ToArray();
         }
 
         private static string MakeOrdinalScriptWithoutKeys(string rawScript, string[] args)
@@ -137,12 +135,9 @@ static ScriptParameterMapper()
         /// <param name="script">The script to prepare.</param>
         public static LuaScript PrepareScript(string script)
         {
-            if (TryExtractParameters(script, out var ps))
-            {
-                var ordinalScript = MakeOrdinalScriptWithoutKeys(script, ps);
-                return new LuaScript(script, ordinalScript, ps);
-            }
-            throw new ArgumentException("Count not parse script: " + script);
+            var ps = ExtractParameters(script);
+            var ordinalScript = MakeOrdinalScriptWithoutKeys(script, ps);
+            return new LuaScript(script, ordinalScript, ps);
         }
 
         private static readonly HashSet<Type> ConvertableTypes = new()

diff --git a/tests/StackExchange.Redis.Tests/Issues/Issue2164.cs b/tests/StackExchange.Redis.Tests/Issues/Issue2164.cs
@@ -0,0 +1,55 @@
+namespace StackExchange.Redis.Tests.Issues
+{
+    public class Issue2164
+    {
+        [Fact]
+        public void LoadSimpleScript()
+        {
+            LuaScript.Prepare("return 42");
+        }
+        [Fact]
+        public void LoadComplexScript()
+        {
+            LuaScript.Prepare(@"
+-------------------------------------------------------------------------------
+-- API definitions
+-------------------------------------------------------------------------------
+local MessageStoreAPI = {}
+
+MessageStoreAPI.confirmPendingDelivery = function(smscMessageId, smscDeliveredAt, smscMessageState)
+    local messageId = redis.call('hget', ""smId:"" .. smscMessageId, 'mId')
+    if not messageId then
+        return nil
+    end
+    -- delete pending delivery
+    redis.call('del', ""smId:"" .. smscMessageId)
+
+    local mIdK = 'm:'..messageId
+
+    local result = redis.call('hsetnx', mIdK, 'sState', smscMessageState)
+    if result == 1 then
+        redis.call('hset', mIdK, 'sDlvAt', smscDeliveredAt)
+        redis.call('zrem', ""msg.validUntil"", messageId)
+        return redis.call('hget', mIdK, 'payload')
+    else
+        return nil
+    end
+end
+
+
+-------------------------------------------------------------------------------
+-- Function lookup
+-------------------------------------------------------------------------------
+
+-- None of the function calls accept keys
+if #KEYS > 0 then error('No Keys should be provided') end
+
+-- The first argument must be the function that we intend to call, and it must
+-- exist
+local command_name = assert(table.remove(ARGV, 1), 'Must provide a command as first argument')
+local command      = assert(MessageStoreAPI[command_name], 'Unknown command ' .. command_name)
+
+return command(unpack(ARGV))");
+        }
+    }
+}