Add ConfigKit validation and diagnostics

config.go

@@ -2,9 +2,11 @@ package commandkit
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"sort"
+	"strconv"
 	"strings"
 
 	configkit "gitea.maximumdirect.net/eric/ConfigKit"
@@ -129,11 +131,22 @@ func RegisterConfig[C any](app *App, suite ConfigSuite[C]) error {
 		return fmt.Errorf("command path %q is already registered", "config")
 	}
 
-	command, err := newConfigScopesCommandWithScopes(normalized.Scopes, nil)
+	commands := make([]Command, 0, 2)
+	installed := make([]ConfigOperation, 0, 1)
+	if configOperationDeclared(normalized.Scopes, ConfigValidate) {
+		validate, err := newConfigValidateCommand(normalized)
+		if err != nil {
+			return err
+		}
+		commands = append(commands, validate)
+		installed = append(installed, ConfigValidate)
+	}
+	command, err := newConfigScopesCommandWithScopes(normalized.Scopes, installed)
 	if err != nil {
 		return err
 	}
-	root, err := Group("config", "Inspect configuration.", command)
+	commands = append(commands, command)
+	root, err := Group("config", "Inspect configuration.", commands...)
 	if err != nil {
 		return err
 	}
@@ -144,6 +157,80 @@ func RegisterConfig[C any](app *App, suite ConfigSuite[C]) error {
 	return nil
 }
 
+// NewConfigKitScope adapts a ConfigKit loader into a configuration scope.
+func NewConfigKitScope[C, T any](name, summary string, load func(context.Context, Selection, C) (*configkit.Result[T], error)) (ConfigScope[C], error) {
+	if load == nil {
+		return ConfigScope[C]{}, fmt.Errorf("ConfigKit scope loader must not be nil")
+	}
+	return ConfigScope[C]{
+		Name:       name,
+		Summary:    summary,
+		Operations: []ConfigOperation{ConfigValidate, ConfigShow, ConfigSources, ConfigExplain},
+		Acquire: func(ctx context.Context, request ConfigRequest, contextValue C) (Acquired[ConfigView], error) {
+			result, err := load(ctx, request.Selection, contextValue)
+			if err != nil {
+				var loadError *configkit.LoadError
+				if errors.As(err, &loadError) {
+					return Acquired[ConfigView]{Diagnostics: ConfigKitDiagnostics(name, loadError.Sources(), loadError.Diagnostics())}, err
+				}
+				return Acquired[ConfigView]{}, err
+			}
+			if result == nil {
+				return Acquired[ConfigView]{}, fmt.Errorf("ConfigKit scope %q returned a nil result", name)
+			}
+			return Acquired[ConfigView]{
+				Value:       ConfigView{Effective: result, Sources: result, Explanation: result},
+				Diagnostics: ConfigKitDiagnostics(name, result.Sources(), result.Diagnostics()),
+			}, nil
+		},
+	}, nil
+}
+
+// ConfigKitDiagnostics groups ConfigKit records with their scope and source legend.
+func ConfigKitDiagnostics(scope string, sources []configkit.SourceInfo, records []configkit.Diagnostic) []Diagnostic {
+	if len(records) == 0 {
+		return nil
+	}
+	severity := configkit.SeverityWarning
+	for _, record := range records {
+		if record.Severity == configkit.SeverityError {
+			severity = configkit.SeverityError
+			break
+		}
+	}
+	return []Diagnostic{{
+		Severity: severity,
+		Write: func(writer io.Writer) error {
+			if err := writeDiagnosticText(writer, "Configuration scope "+strconv.Quote(scope)+":\n"); err != nil {
+				return err
+			}
+			if len(sources) > 0 {
+				if err := writeDiagnosticText(writer, "Source IDs:\n"); err != nil {
+					return err
+				}
+				for _, source := range sources {
+					line := "  " + strconv.Quote(source.ID) + ": label=" + strconv.Quote(source.Label) + ", path=" + strconv.Quote(source.Path) + "\n"
+					if err := writeDiagnosticText(writer, line); err != nil {
+						return err
+					}
+				}
+			}
+			return configkit.WriteDiagnostics(writer, records)
+		},
+	}}
+}
+
+func writeDiagnosticText(writer io.Writer, value string) error {
+	written, err := io.WriteString(writer, value)
+	if err != nil {
+		return err
+	}
+	if written != len(value) {
+		return io.ErrShortWrite
+	}
+	return nil
+}
+
 func normalizeConfigSuite[C any](suite ConfigSuite[C]) (ConfigSuite[C], error) {
 	normalized := suite
 	normalized.Selectors = append([]Selector[C](nil), suite.Selectors...)