Preserve exact null parameter names in DI and hosting extensions

Author: ZelAnton

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 
 ### Fixed
+- DI and Hosting registration extensions now preserve each null argument's public parameter name in `ArgumentNullException.ParamName`.
 - Fixed the `AddProcessKitGroup` configuration overload to report `services` as the null argument.
 - Runners registered by `AddProcessKit` and `AddProcessKitGroup` now reject a null command synchronously with `ArgumentNullException` naming `command` before applying defaults, logging, cancellation, or invoking the underlying runner.
 - `AddProcessKitClient(..., configure)` now rejects a null configured client with `ArgumentNullException` naming `configure` when the keyed client is resolved, instead of reporting a missing keyed registration.

README.md

@@ -1079,6 +1079,10 @@ container has an `ILoggerFactory`). The runners registered by `AddProcessKit()`
 (`ParamName = "command"`) before applying defaults or logging and before delegating to their
 underlying runner. A keyed `AddProcessKitClient(..., configure)` callback must likewise return a
 non-null `CliClient`; resolution rejects a null result with `ArgumentNullException` naming `configure`.
+The DI registration overloads also name each null argument after their public signatures
+(`services`, `configure`, `configuration`, `name`, or `program`); the Hosting registration and
+configuration overloads do the same for `services`, `name`, `command`, `configureSupervisor`, and
+`configure`.
 
 *Deeper: [Observability](docs/observability.md).*
 

docs/dependency-injection.md

@@ -61,6 +61,11 @@ builder. The callback runs when the keyed client is resolved and must return a n
 null result is rejected with `ArgumentNullException` naming `configure` instead of being reported as a
 missing keyed registration.
 
+Across the DI registration overloads, a null argument is rejected with `ArgumentNullException` whose
+`ParamName` matches the public signature: `services`, `configure`, `configuration`, `name`, or
+`program`. The configured-client result check above remains deferred until keyed-client resolution and
+names the callback parameter, `configure`.
+
 ```csharp
 services.AddProcessKit();
 services.AddProcessKitClient("git", "git", c => c.WithDefaults(cmd => cmd.CurrentDir("/repo")));
@@ -115,6 +120,11 @@ services.ConfigureProcessKitHostedProcess("worker", o =>
 });
 ```
 
+These Hosting extensions preserve the same diagnostic contract: a null argument reports its public
+parameter name (`services`, `name`, `command`, `configureSupervisor`, or `configure`) from
+`AddProcessKitHostedProcess`, `ConfigureProcessKitHostedProcess`, and
+`AddProcessKitHostedProcessHealthCheck`.
+
 Resolve `HostedProcessService` by the same key when you need the last `SupervisionOutcome` or stop
 outcome for health reporting. It also exposes live supervision telemetry — `IsSupervisionActive`,
 `RestartCount`, `IsStormPaused` — for anything that wants to observe the child without waiting for

src/ProcessKit.Extensions.DependencyInjection/ServiceCollectionExtensions.fs

@@ -121,7 +121,7 @@ type ServiceCollectionExtensions =
         (services: IServiceCollection, configure: Action<ProcessKitOptions>)
         : IServiceCollection =
         ArgumentNullException.ThrowIfNull(services, nameof services)
-        ArgumentNullException.ThrowIfNull configure
+        ArgumentNullException.ThrowIfNull(configure, nameof configure)
         services.Configure configure |> ignore
         ServiceCollectionExtensions.AddProcessKit services
 
@@ -135,7 +135,7 @@ type ServiceCollectionExtensions =
     [<RequiresDynamicCode "Binds ProcessKitOptions from IConfiguration by reflection; use the Action<ProcessKitOptions> overload in a NativeAOT app.">]
     static member AddProcessKit(services: IServiceCollection, configuration: IConfiguration) : IServiceCollection =
         ArgumentNullException.ThrowIfNull(services, nameof services)
-        ArgumentNullException.ThrowIfNull configuration
+        ArgumentNullException.ThrowIfNull(configuration, nameof configuration)
         services.Configure<ProcessKitOptions> configuration |> ignore
         ServiceCollectionExtensions.AddProcessKit services
 
@@ -161,9 +161,9 @@ type ServiceCollectionExtensions =
         (services: IServiceCollection, name: string, program: string, configure: Func<CliClient, CliClient>)
         : IServiceCollection =
         ArgumentNullException.ThrowIfNull(services, nameof services)
-        ArgumentNullException.ThrowIfNull name
-        ArgumentNullException.ThrowIfNull program
-        ArgumentNullException.ThrowIfNull configure
+        ArgumentNullException.ThrowIfNull(name, nameof name)
+        ArgumentNullException.ThrowIfNull(program, nameof program)
+        ArgumentNullException.ThrowIfNull(configure, nameof configure)
 
         if DiInternals.hasClient services name then
             raise (
@@ -221,7 +221,7 @@ type ServiceCollectionExtensions =
         (services: IServiceCollection, configure: Action<ProcessKitOptions>)
         : IServiceCollection =
         ArgumentNullException.ThrowIfNull(services, nameof services)
-        ArgumentNullException.ThrowIfNull configure
+        ArgumentNullException.ThrowIfNull(configure, nameof configure)
         services.Configure configure |> ignore
         ServiceCollectionExtensions.AddProcessKitGroup services
 
@@ -235,6 +235,6 @@ type ServiceCollectionExtensions =
     [<RequiresDynamicCode "Binds ProcessKitOptions from IConfiguration by reflection; use the Action<ProcessKitOptions> overload in a NativeAOT app.">]
     static member AddProcessKitGroup(services: IServiceCollection, configuration: IConfiguration) : IServiceCollection =
         ArgumentNullException.ThrowIfNull(services, nameof services)
-        ArgumentNullException.ThrowIfNull configuration
+        ArgumentNullException.ThrowIfNull(configuration, nameof configuration)
         services.Configure<ProcessKitOptions> configuration |> ignore
         ServiceCollectionExtensions.AddProcessKitGroup services

src/ProcessKit.Extensions.Hosting/HostedServiceCollectionExtensions.fs

@@ -46,10 +46,10 @@ type HostedServiceCollectionExtensions =
     [<Extension>]
     static member AddProcessKitHostedProcess
         (services: IServiceCollection, name: string, command: Command, configureSupervisor: Func<Supervisor, Supervisor>) : IServiceCollection =
-        ArgumentNullException.ThrowIfNull services
-        ArgumentNullException.ThrowIfNull name
-        ArgumentNullException.ThrowIfNull command
-        ArgumentNullException.ThrowIfNull configureSupervisor
+        ArgumentNullException.ThrowIfNull(services, nameof services)
+        ArgumentNullException.ThrowIfNull(name, nameof name)
+        ArgumentNullException.ThrowIfNull(command, nameof command)
+        ArgumentNullException.ThrowIfNull(configureSupervisor, nameof configureSupervisor)
 
         if Registration.hasHostedProcess services name then
             raise (
@@ -103,9 +103,9 @@ type HostedServiceCollectionExtensions =
     static member ConfigureProcessKitHostedProcess
         (services: IServiceCollection, name: string, configure: Action<HostedProcessOptions>)
         : IServiceCollection =
-        ArgumentNullException.ThrowIfNull services
-        ArgumentNullException.ThrowIfNull name
-        ArgumentNullException.ThrowIfNull configure
+        ArgumentNullException.ThrowIfNull(services, nameof services)
+        ArgumentNullException.ThrowIfNull(name, nameof name)
+        ArgumentNullException.ThrowIfNull(configure, nameof configure)
 
         services.Configure(name, configure) |> ignore
         services
@@ -121,8 +121,8 @@ type HostedServiceCollectionExtensions =
     static member AddProcessKitHostedProcessHealthCheck
         (services: IServiceCollection, name: string)
         : IServiceCollection =
-        ArgumentNullException.ThrowIfNull services
-        ArgumentNullException.ThrowIfNull name
+        ArgumentNullException.ThrowIfNull(services, nameof services)
+        ArgumentNullException.ThrowIfNull(name, nameof name)
 
         services.TryAddKeyedSingleton<HostedProcessHealthCheck>(
             name,

tests/ProcessKit.CSharp.Tests/DependencyInjectionTests.cs

@@ -23,6 +23,12 @@ namespace ProcessKit.CSharp.Tests;
 [TestFixture]
 public class DependencyInjectionTests
 {
+    private static void AssertNullParameter(string expected, Action call)
+    {
+        var exception = Assert.Throws<ArgumentNullException>(call);
+        Assert.That(exception!.ParamName, Is.EqualTo(expected));
+    }
+
     private sealed class SingleValueConfiguration(string key, string? value) : IConfiguration
     {
         private readonly IConfigurationSection section = new SingleValueConfigurationSection(key, value);
@@ -157,6 +163,37 @@ public void AddProcessKitClient_rejects_a_null_configure_result_when_the_keyed_c
         Assert.That(exception!.ParamName, Is.EqualTo("configure"));
     }
 
+    [Test]
+    public void DI_extension_null_guards_preserve_their_public_parameter_names()
+    {
+        var services = new ServiceCollection();
+
+        AssertNullParameter(
+            "services",
+            () => ServiceCollectionExtensions.AddProcessKit(null!));
+        AssertNullParameter(
+            "configure",
+            () => services.AddProcessKit((Action<ProcessKitOptions>)null!));
+        AssertNullParameter(
+            "configuration",
+            () => services.AddProcessKit((IConfiguration)null!));
+        AssertNullParameter(
+            "name",
+            () => services.AddProcessKitClient(null!, "tool", client => client));
+        AssertNullParameter(
+            "program",
+            () => services.AddProcessKitClient("tool", null!, client => client));
+        AssertNullParameter(
+            "configure",
+            () => services.AddProcessKitClient("tool", "tool", (Func<CliClient, CliClient>)null!));
+        AssertNullParameter(
+            "configure",
+            () => services.AddProcessKitGroup((Action<ProcessKitOptions>)null!));
+        AssertNullParameter(
+            "configuration",
+            () => services.AddProcessKitGroup((IConfiguration)null!));
+    }
+
     [Test]
     public void AddProcessKit_with_a_configure_action_binds_ProcessKitOptions_defaults()
     {

tests/ProcessKit.Tests/DependencyInjectionTests.fs

@@ -91,6 +91,14 @@ type DependencyInjectionTests() =
 
             Assert.That(thrown.ParamName, Is.EqualTo "command", verb)
 
+    let assertNullParameter (caseName: string) (expected: string) (call: unit -> unit) =
+        let thrown =
+            match Assert.Throws<ArgumentNullException>(Action call) with
+            | null -> failwith $"Expected {caseName} to reject a null {expected}."
+            | exceptionThrown -> exceptionThrown
+
+        Assert.That(thrown.ParamName, Is.EqualTo expected, caseName)
+
     /// Poll until `pid` is no longer a live process (reaped/exited), or the deadline elapses.
     let waitProcessGone (pid: int) (deadlineMs: int) : Task<bool> =
         task {
@@ -240,6 +248,79 @@ type DependencyInjectionTests() =
 
         Assert.That(thrown.ParamName, Is.EqualTo "services")
 
+    [<Test>]
+    member _.``DI extension null guards preserve their public parameter names``() =
+        let services = ServiceCollection() :> IServiceCollection
+        let clientConfigure = Func<CliClient, CliClient>(id)
+
+        let calls: (string * string * (unit -> unit)) list =
+            [ "AddProcessKit configure",
+              "configure",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKit(services, Unchecked.defaultof<Action<ProcessKitOptions>>)
+                  |> ignore)
+              "AddProcessKit configuration",
+              "configuration",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKit(services, Unchecked.defaultof<IConfiguration>)
+                  |> ignore)
+              "AddProcessKitClient services",
+              "services",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitClient(
+                      Unchecked.defaultof<IServiceCollection>,
+                      "tool",
+                      "tool",
+                      clientConfigure
+                  )
+                  |> ignore)
+              "AddProcessKitClient name",
+              "name",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitClient(
+                      services,
+                      Unchecked.defaultof<string>,
+                      "tool",
+                      clientConfigure
+                  )
+                  |> ignore)
+              "AddProcessKitClient program",
+              "program",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitClient(
+                      services,
+                      "tool",
+                      Unchecked.defaultof<string>,
+                      clientConfigure
+                  )
+                  |> ignore)
+              "AddProcessKitClient configure",
+              "configure",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitClient(
+                      services,
+                      "tool",
+                      "tool",
+                      Unchecked.defaultof<Func<CliClient, CliClient>>
+                  )
+                  |> ignore)
+              "AddProcessKitGroup configure",
+              "configure",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitGroup(
+                      services,
+                      Unchecked.defaultof<Action<ProcessKitOptions>>
+                  )
+                  |> ignore)
+              "AddProcessKitGroup configuration",
+              "configuration",
+              (fun () ->
+                  ServiceCollectionExtensions.AddProcessKitGroup(services, Unchecked.defaultof<IConfiguration>)
+                  |> ignore) ]
+
+        for caseName, expected, call in calls do
+            assertNullParameter caseName expected call
+
     [<Test>]
     member _.``the resolved runner is logger-aware when a logger factory is registered``() : Task =
         task {

tests/ProcessKit.Tests/HostedProcessHealthCheckTests.fs

@@ -62,6 +62,32 @@ type HostedProcessHealthCheckTests() =
         let healthCheck = provider.GetRequiredKeyedService<HostedProcessHealthCheck> name
         provider, hosted, service, healthCheck :> IHealthCheck
 
+    let assertNullParameter (caseName: string) (expected: string) (call: unit -> unit) =
+        let thrown =
+            match Assert.Throws<ArgumentNullException>(Action call) with
+            | null -> failwith $"Expected {caseName} to reject a null {expected}."
+            | exceptionThrown -> exceptionThrown
+
+        Assert.That(thrown.ParamName, Is.EqualTo expected, caseName)
+
+    [<Test>]
+    member _.``Hosted-process health-check extension preserves its public null parameter names``() =
+        let services = ServiceCollection() :> IServiceCollection
+
+        assertNullParameter "services" "services" (fun () ->
+            HostedServiceCollectionExtensions.AddProcessKitHostedProcessHealthCheck(
+                Unchecked.defaultof<IServiceCollection>,
+                "worker"
+            )
+            |> ignore)
+
+        assertNullParameter "name" "name" (fun () ->
+            HostedServiceCollectionExtensions.AddProcessKitHostedProcessHealthCheck(
+                services,
+                Unchecked.defaultof<string>
+            )
+            |> ignore)
+
     [<Test>]
     member _.``AddProcessKitHostedProcessHealthCheck registers a keyed IHealthCheck resolvable by the same name``() =
         let services = ServiceCollection()