Report missing build parameter references clearly

src/Invex.Atom.Build/BuildResolver.cs

@@ -99,7 +99,7 @@ public BuildModel Resolve()
                 var usedParams = new List<UsedParam>();
 
                 foreach (var param in x.Params)
-                    AddParamAndChildren(param.Param, param.Required, usedParams, paramModels, []);
+                    AddParamAndChildren(x.Name, param.Param, param.Required, usedParams, paramModels, []);
 
                 return new TargetModel(x.Name, x.Description, x.Hidden)
                 {
@@ -261,12 +261,14 @@ void Visit(TargetModel target)
     /// <summary>
     ///     Recursively adds a parameter and its chained dependencies to the list of used parameters for a target.
     /// </summary>
+    /// <param name="target">The name of the target that references the parameter.</param>
     /// <param name="param">The name of the parameter to add.</param>
     /// <param name="required">A value indicating whether the parameter is required.</param>
     /// <param name="usedParams">The list of used parameters to add to.</param>
     /// <param name="paramModels">A dictionary of all available parameter models.</param>
     /// <param name="visited">A set of already-visited parameter names to detect and prevent circular chains.</param>
     private static void AddParamAndChildren(
+        string target,
         string param,
         bool required,
         List<UsedParam> usedParams,
@@ -276,10 +278,13 @@ private static void AddParamAndChildren(
         if (!visited.Add(param))
             return;
 
-        var model = paramModels[param];
+        if (!paramModels.TryGetValue(param, out var model))
+            throw new BuildConfigurationException(
+                $"Target '{target}' references parameter '{param}' which is not defined in the build.");
+
         usedParams.Add(new(model, required));
 
         foreach (var chainedParam in model.ChainedParams)
-            AddParamAndChildren(chainedParam, required, usedParams, paramModels, visited);
+            AddParamAndChildren(target, chainedParam, required, usedParams, paramModels, visited);
     }
 }

tests/Invex.Atom.Build.Tests/ClassTests/Build/BuildResolverTests.cs

@@ -240,6 +240,28 @@ public void Resolve_WithMissingDependency_ThrowsException()
         ex.Message.ShouldContain("depends on target 'Target2' which does not exist");
     }
 
+    [Test]
+    public void Resolve_WithMissingParam_ThrowsException()
+    {
+        // Arrange
+        var buildDefinition = new TestBuildDefinition(_services)
+        {
+            ManualTargetDefinitions = new Dictionary<string, Target>
+            {
+                ["Target1"] = t => t.RequiresParam("MissingParam"),
+            },
+        };
+
+        var commandLineArgs = new CommandLineArgs(true, [new CommandArg("Target1")]);
+        var paramService = A.Fake<IParamService>();
+        var logger = A.Fake<ILogger<BuildResolver>>();
+        var buildResolver = new BuildResolver(buildDefinition, paramService, commandLineArgs, logger);
+
+        // Act & Assert
+        var ex = Should.Throw<BuildConfigurationException>(buildResolver.Resolve);
+        ex.Message.ShouldBe("Target 'Target1' references parameter 'MissingParam' which is not defined in the build.");
+    }
+
     [Test]
     public void Resolve_WithComplexCircularDependency_ThrowsException()
     {