Harden the runner contract

internal/framework/runner/runner.go

@@ -56,6 +56,9 @@ func (r *Runner) Run(ctx context.Context, input RunInput) (RunOutput, error) {
 		if err != nil {
 			return output, fmt.Errorf("build extractor %q: %w", extractorKey, err)
 		}
+		if extractor == nil {
+			return output, fmt.Errorf("build extractor %q: returned nil extractor", extractorKey)
+		}
 
 		result, err := extractor.Extract(ctx, contracts.ExtractionRequest{
 			Source:    input.Source,
@@ -121,7 +124,10 @@ func runValidators(ctx context.Context, extractor contracts.Extractor, doc *sour
 	var rejected []artifacts.RejectedArtifact
 	var warnings []contracts.Warning
 
-	for _, validator := range extractor.Validators() {
+	for validatorIndex, validator := range extractor.Validators() {
+		if validator == nil {
+			return nil, rejected, warnings, fmt.Errorf("extractor %q validator[%d] must not be nil", extractor.Key(), validatorIndex)
+		}
 		result, err := validator.Validate(ctx, contracts.ValidationRequest{
 			Source:     doc,
 			Candidates: eligible,

internal/framework/runner/runner_test.go

@@ -83,6 +83,19 @@ func TestRunRejectsInvalidSetup(t *testing.T) {
 	}
 }
 
+func TestRunRejectsNilExtractorFromFactory(t *testing.T) {
+	factory := fakeFactory{extractors: map[string]contracts.Extractor{
+		"generic-extractor": nil,
+	}}
+
+	_, err := New(factory).Run(context.Background(), RunInput{
+		Source:        validSourceDocument(),
+		ExtractorKeys: []string{"generic-extractor"},
+	})
+
+	assertRunError(t, err, "returned nil extractor")
+}
+
 func TestRunUsesConfiguredExtractorOrderAndAssignsGlobalIndices(t *testing.T) {
 	var order []string
 	var seenIndices []int
@@ -251,6 +264,25 @@ func TestRunSurfacesValidatorCardinalityError(t *testing.T) {
 	assertRunError(t, err, "0 decisions for 1 candidates")
 }
 
+func TestRunRejectsNilValidator(t *testing.T) {
+	factory := fakeFactory{extractors: map[string]contracts.Extractor{
+		"generic-extractor": fakeExtractor{
+			key:            "generic-extractor",
+			artifactType:   "generic-artifact",
+			schemaVersion:  "v1",
+			candidateCount: 1,
+			validators:     []contracts.Validator{nil},
+		},
+	}}
+
+	_, err := New(factory).Run(context.Background(), RunInput{
+		Source:        validSourceDocument(),
+		ExtractorKeys: []string{"generic-extractor"},
+	})
+
+	assertRunError(t, err, "validator[0] must not be nil")
+}
+
 func TestRunCollectsExtractorAndValidatorWarnings(t *testing.T) {
 	validator := fakeValidator{
 		name:      "generic-validator",