commandkit/docs/consumers/guide.md

Consumer guide

CommandKit is distributed as three Go modules. Start with the core and add an integration module only when the application uses that library. Core and integration command factories return canonical commandkit.Command values. Applications may install those alongside application-owned RoutingRule declarations through commandkit.New or App.Register; routing rules are installed at the application root, not as group children.

Module selection

Import	Use when
gitea.maximumdirect.net/eric/CommandKit	The application needs typed command declarations and common CLI behavior.
gitea.maximumdirect.net/eric/CommandKit/integrations/ckconfig	The application wants ConfigKit-backed configuration scopes and reports.
gitea.maximumdirect.net/eric/CommandKit/integrations/ckprompt	The application wants PromptKit engine configuration/comparison, five catalogs, named inspection, requirements discovery, request validation, or native smoke testing.

The two integrations are independent optional imports. ckprompt uses the public scope and error contracts from ckconfig; importing it does not add the config family. An application that wants both families passes both returned declarations to core. The maintained examples show core-only, ConfigKit-only, and composed applications.

Go compatibility

All three modules declare a consumer minimum of Go 1.26.0. The root module also selects ReleaseKit v0.4.2 as a Go tool, which makes that tool's module graph part of the root consumer module requirements even though production packages do not import ReleaseKit. The release policy defines the support assumption. Maintainers use Go 1.26.8 for validation and publication; see the release procedure.

Core commands

Declare typed flags and operands with CommandSpec[I], then capture them with NewCommand. Bindings deliver Supplied[T], which distinguishes an omitted default from an explicitly supplied empty, false, or zero value.

package example

import (
	"fmt"
	"strconv"

	commandkit "gitea.maximumdirect.net/eric/CommandKit"
)

type GreetInput struct {
	Count commandkit.Supplied[int]
}

func Greeting() commandkit.Command {
	countDefault := 1
	return commandkit.NewCommand(commandkit.CommandSpec[GreetInput]{
		Name: "greet", Summary: "Write a greeting.",
		Flags: []commandkit.Flag[GreetInput]{
			commandkit.ValueFlag(
				commandkit.FlagMeta{Name: "count", Usage: "Number of greetings."},
				&countDefault, strconv.Atoi,
				func(input *GreetInput, value commandkit.Supplied[int]) {
					input.Count = value
				},
			),
		},
		Run: func(invocation commandkit.Invocation, input GreetInput) commandkit.Outcome {
			if _, err := fmt.Fprintln(invocation.Reporter().Output(), input.Count.Value); err != nil {
				return commandkit.Failure("Could not write the greeting.").WithCause(err)
			}
			return commandkit.Success()
		},
	})
}

The application supplies context.Context, argv without the executable name, and output streams to App.Execute; it decides how the returned status maps to process exit. New installs generated help/version and caller declarations as one batch. Register validates each call as a batch before changing that App. Invalid declaration errors retain their wrapped identity for errors.Is and errors.As.

Declarations copy their metadata and slice inputs when captured, retain callback references, and can be reused across applications. Copies of a typed binding preserve its identity; a separately constructed lookalike does not. Supplied values convert before input construction. A command's NewInput creates input only when execution reaches it; help does not construct caller input or run provider callbacks.

Invocation reporting

Invocation.Reporter() supplies the reporter for the current handler. Use Output() or RenderOutput() for substantive results; use Warn, Info, Progress, and Debug for categorized messages. Queue a summary with AtEnd().Info when it belongs after the handler returns. The CLI reference owns flag grammar, visibility, prefixes, and status behavior.

Return terminal text with Failure(message, details...), Usage(message, details...), or WithExplanation on a domain outcome. Attach an optional Go error separately with WithCause. A cause is preserved for inspection, but it does not choose the outcome or become user-facing text. Rendering callbacks write to their supplied writer only while the callback runs; they must not submit another message or start another rendering operation through the same reporter.

Run: func(invocation commandkit.Invocation, input GreetInput) commandkit.Outcome {
	if _, err := fmt.Fprintln(invocation.Reporter().Output(), input.Count.Value); err != nil {
		return commandkit.Failure("Could not write the greeting.").WithCause(err)
	}
	return commandkit.Success()
}

After App.Execute, inspect the returned Outcome. Its Cause retains the operation error; Presentation.Output and Presentation.Diagnostics report delivery state and the first rendering or write errors for their destinations. CommandKit does not retain a message transcript. Reporter operations for one invocation are safe concurrently, but concurrent submission order is not specified. The caller owns the writers passed to Execute; CommandKit does not close them.

Migrating from the previous reporting API

Previous API	Current API
invocation.Streams.Out / .Err	invocation.Reporter().Output() and categorized reporter methods. Streams remains the argument to App.Execute.
Failure(err) / Usage(err)	Failure("operator-facing explanation").WithCause(err) / Usage("usage explanation").WithCause(err). Choose the explanation deliberately; the cause alone is not printed.
Outcome.Diagnostics or terminal SeverityError	Submit independent messages through reporter methods. Put failure context in Explanation; provider Acquired.Diagnostics remains passive data for the owning integration to submit.
ReportIncomplete, DiagnosticDelivery, or DeliveryError	Inspect Outcome.Presentation.Output and .Diagnostics, including each DeliveryResult.State, RenderError, and WriteError.

Application-owned aliases

Pass commands and aliases together as declarations. Integration factories can be called directly in the installation list, and command-scoped flag aliases name the canonical command path:

app, err := commandkit.New(
	identity,
	ckprompt.Command(suite),
	commandkit.Alias("pk", "promptkit"),
	commandkit.FlagAliasFor("promptkit show prompt", "--fmt", "--format"),
)

For a reusable collection, use []commandkit.Declaration. Go does not expand a []commandkit.Command into ...commandkit.Declaration, so convert command-only slices when composing them with routing rules:

commands := []commandkit.Command{ckprompt.Command(suite)}
declarations := make([]commandkit.Declaration, 0, len(commands)+1)
for _, command := range commands {
	declarations = append(declarations, command)
}
declarations = append(declarations, commandkit.Alias("pk", "promptkit"))
app, err := commandkit.New(identity, declarations...)

New and Register validate each supplied batch before publishing its commands and routing rules. Factories capture their inputs eagerly; malformed or conflicting rules are reported at installation. Identical rules are safe to contribute from reusable helpers. The core example and composed consumer show complete maintained wiring with ordinary command behavior alongside aliases. The Go declarations and GoDoc own the public API contracts; the CLI reference owns routing and operator-visible behavior.

ConfigKit scopes

For an application with one ordinary app configuration loader, ckconfig.AppCommand supplies the state-free convenience declaration:

app, err := commandkit.New(
	commandkit.Identity{Name: "Example", Version: "dev"},
	ckconfig.AppCommand(loadAppConfig),
)

loadAppConfig has the signature func(context.Context, ckconfig.Selection) (*configkit.Result[T], error). Construction, installation, and help do not call it. Selection preserves whether config and overlay paths were explicitly supplied, including empty values.

Use ckconfig.Command(ckconfig.Suite[I, S]{...}) when the application needs multiple named scopes, selector flags, scope-aware input checks, or shared acquisition state or a custom comparison provider. A declared Diff capability uses Scope.Compare; ckconfig.FromConfigKit and AppCommand provide the ConfigKit-backed implementation. Each comparison side gets its own initialized and checked input, while state is shared by the invocation. Factory results remain caller-owned, so separate initialization calls do not guarantee distinct objects. See ckconfig.Suite's GoDoc for factory timing, omitted-factory zero values (including nil pointers), and ownership. The application owns the state type and what it caches. ckconfig.FromConfigKit adapts a typed ConfigKit loader without calling it during construction.

The config family provides scope discovery, validation, native effective YAML, source inventory, path explanation, and ConfigKit-backed comparison for the capabilities declared by its scopes. The CLI reference owns operator syntax and report details.

PromptKit configuration, definitions, and requirements

ckprompt.ConfigScope(loadEngine) returns a ckconfig.Scope for the PromptKit engine's captured configuration. Add that scope to a ckconfig.Suite to expose it under config with validate/show/sources/explain and native diff operations; it does not install PromptKit catalog, definition, or requirements commands.

ckprompt.FromEngine(loadEngine) supplies eight callbacks: prompt, profile, backend, namespace, and collection catalogs; named prompt and profile inspection; and native requirements discovery. Concrete request validation and smoke testing are separate capabilities, added explicitly with ckprompt.WithRequestValidation and ckprompt.WithSmokeTesting. The suite has ten independently optional callbacks in total. ckprompt.Command(suite) creates only operations whose callbacks are present; discovery, validation, and smoke testing can be installed independently. A composed suite can enable both additional operations:

suite := ckprompt.FromEngine(loadEngine)
suite = ckprompt.WithRequestValidation(suite, loadEngine, buildRequest)
suite = ckprompt.WithSmokeTesting(suite, loadEngine, nil)
suite.NewInput = newInput
suite.NewState = newState
suite.Selectors = selectors
definitionCommand := ckprompt.Command(suite)

A validation-only suite can start empty. With application types named Input and State, a nil builder forwards the request fields populated by standard flags directly to PromptKit:

suite := ckprompt.WithRequestValidation(
	ckprompt.Suite[Input, State]{}, loadEngine, nil,
)
validationCommand := ckprompt.Command(suite)

If the loader is nil, the returned suite retains a wiring issue for installation to report, even if capabilities are narrowed later. A builder runs before the engine loader and receives the seed request, selection, typed input, shared state, and invocation context. It returns the concrete request; the adapter does not merge seed fields back afterward. The loader receives the original selection. Builders should start from the seed, preserve operator values and bindings, and apply defaults only when a map key is absent, so explicitly supplied empty values stay meaningful. Applications that validate and then execute a request are encouraged to share their request construction logic between those paths.

The eight catalog and inspection callbacks and the two explicit additions are independently optional. For catalogs without named or requirements inspection, narrow the suite before command capture:

definitions := ckprompt.FromEngine(loadEngine)
definitions.InspectPrompt = nil
definitions.InspectProfile = nil
definitions.InspectRequirements = nil
definitionCommand := ckprompt.Command(definitions)

Each selected inspection, requirements, validation, smoke, or catalog operation prepares one input, applies its captured selectors, checks that input, and initializes one state value when those steps are reached. The bundled validation adapter delegates concrete request preparation to PromptKit and carries its native errors plus engine-loading diagnostics through the acquisition. It does not call the model or retain a prepared execution snapshot. See ckprompt.Suite's GoDoc for factory timing, omitted-factory zero values, and caller-owned objects and effects. The loader receives invocation context, explicitly supplied selection, input, and state. FromEngine uses PromptKit's public listing and inspection methods, including Engine.InspectRequirements; validation must be opted into separately and uses Engine.ValidateRequest.

Catalog, named definition inspection, and requirements discovery do not render messages or load request artifacts. Concrete request validation follows native PromptKit preparation, which can resolve prompt/profile resources, load artifacts and schemas, render messages, and perform applicable configuration and credential checks. It does not make a model call or certify that a later execution will succeed. Application loaders and direct callbacks retain their own effects. Smoke testing explicitly invokes one native PromptKit diagnostic or all four in order. Native inference checks use the configured public promptkit.LLMClient; applications retain ownership of client and probe configuration. A builder may customize the seeded native request, and its complete return value is authoritative. The CLI reference, definition inspection, and requirements contract own operator syntax and reports.

The composed example combines app and PromptKit config scopes, comparison and catalogs, named and requirements inspection, request validation, smoke testing, and an application-owned session restore command.

Outcomes and ownership

Core classifies usage and operational failures while preserving application domain outcomes and supported error identity. Applications choose domain classification and status. A terminal explanation is presented separately from the optional operation cause, while report and diagnostic delivery observations are available in Outcome.Presentation. The caller owns process startup, signal handling, and exit mapping; Execute never exits the process.

Go declarations and GoDoc own exact exported contracts. ConfigKit owns configuration decoding, validation, and provenance. PromptKit owns prompt formats, profile resolution, and inspection details. See the ConfigKit v0.8.0 inspection API, PromptKit engine methods, configuration inspection, smoke diagnostics, and PromptKit v0.16.0 consumer guidance.