ApplyAPIConverters does not flatten NestingModeSingle (SchemaTypeObject) blocks in generated examples

[Duologic]

Summary

ApplyAPIConverters (added in #538) correctly flattens single-element arrays for TypeList/TypeSet with MaxItems=1 fields in generated example manifests. However, it does not handle SchemaTypeObject fields (Terraform plugin framework's NestingModeSingle blocks), which also need flattening.

Background

The HCL-to-JSON scraper always wraps Terraform blocks in arrays per HCL spec. For NestingModeSingle blocks, upjet maps these to SchemaTypeObject (ValueType 9) and generates CRD types as embedded objects (pointer-to-struct), not slices. But the generated example manifests retain the array syntax from the scraper, producing invalid YAML that fails with "unknown field" errors when applied.

Why this doesn't affect AWS/GCP/Azure providers

Those providers use the older SDK v2 TypeList + MaxItems=1 pattern. The SingletonListEmbedder + ApplyAPIConverters pipeline handles that correctly because:

1. SingletonListEmbedder registers conversion paths with [*] wildcards for TypeList/TypeSet fields
2. conversion.Convert uses fieldpath.Pave to traverse these paths and flatten arrays

For SchemaTypeObject fields, SingletonListEmbedder correctly skips them (they're already objects in the CRD). But the traverser does NOT add [*] wildcards to SchemaTypeObject paths, so conversion.Convert fails with "not an object" when trying to traverse the arrays that remain in the scraped examples.

Who is affected

Any upjet-based provider whose Terraform provider uses the plugin framework NestingModeSingle pattern instead of the older TypeList + MaxItems=1 pattern. The grafana/crossplane-provider-grafana provider is the first to hit this (grafana/crossplane-provider-grafana#549).

Workaround

We added a post-processing step in our generator that uses upjet's schema traverser to collect CRD paths for SchemaTypeObject fields, then walks generated example YAML files and flattens single-element arrays at those paths (grafana/crossplane-provider-grafana#557).

Expected behavior

ApplyAPIConverters (or a related utility) should also handle SchemaTypeObject fields by flattening single-element arrays in generated examples to plain objects, matching the CRD's pointer-to-struct type.

Related

• Rename examples/conversion.ConvertSingletonListToEmbeddedObject as ApplyAPIConverters #538 - Added ApplyAPIConverters for TypeList/TypeSet with MaxItems=1
• fix(tfjson): Reset Computed flag for SchemaNestingModeSingle blocks with required children #593 - NestingModeSingle Computed flag
• examples-generated contain fields with wrong type #345 - Wrong types in generated examples

[Duologic]

I have a draft PR that supposedly fixes this, LLM generated, this'll need someone with more domain knowledge to verify that this is a reasonable path to be on.