Preserve owning categories in public errors

nested_error_contract_test.go

@@ -0,0 +1,35 @@
+package promptkit_test
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"go.maximumdirect.net/promptkit"
+)
+
+type nestedErrorReader struct{ cause error }
+
+func (r nestedErrorReader) Read(context.Context, promptkit.ArtifactRef) (*promptkit.Artifact, error) {
+	return nil, r.cause
+}
+
+func TestNestedEngineErrorKeepsOwningOperation(t *testing.T) {
+	child := newSimpleEngine(t, "child")
+	_, childErr := child.Run(context.Background(), promptkit.RunRequest{PromptID: "missing"})
+	if !errors.Is(childErr, promptkit.ErrPromptNotFound) {
+		t.Fatalf("child error = %v", childErr)
+	}
+	client := &fakeLLMClient{err: childErr}
+	parent := newSimpleEngine(t, "hello", promptkit.WithLLMClient(client))
+	_, err := parent.Run(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+	if !errors.Is(err, promptkit.ErrLLMGenerate) || !errors.Is(err, childErr) || !errors.Is(err, promptkit.ErrPromptNotFound) {
+		t.Fatalf("generation error = %v", err)
+	}
+
+	readerParent := newSimpleEngine(t, "hello", promptkit.WithArtifactReader(nestedErrorReader{cause: childErr}))
+	_, err = readerParent.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt", Inputs: map[string]promptkit.ArtifactRef{"extra": promptkit.Inline("data")}})
+	if !errors.Is(err, promptkit.ErrArtifactLoad) || !errors.Is(err, childErr) || !errors.Is(err, promptkit.ErrPromptNotFound) {
+		t.Fatalf("artifact error = %v", err)
+	}
+}