Rust: avro_annotation output fails to compile (lazy_static SCHEMA inside impl) for enum/union schemas

[clemensv]

Summary

convert_avro_schema_to_rust(..., avro_annotation=True, serde_annotation=True) produces a Rust data crate that fails to compile for real-world multi-type schemas that include enums/unions. The Serde-only output (avro_annotation=False) compiles and works correctly; only the Avro-annotation path is affected.

This blocks enabling Avro binary encoding for Rust in the xRegistry code generator (xregistry/codegen#542); we currently have to force avro_annotation=False for Rust as a workaround.

Version

• avrotize 3.8.0
• rustc / cargo 1.92.0 (stable), edition 2021

Reproduction

Generate a Rust data crate with Avro annotations from a schema set that contains enums/unions (the xRegistry lightbulb.xreg.json sample reproduces it), then cargo build:

from avrotize import convert_avro_schema_to_rust
# schema list containing records + enums/unions
convert_avro_schema_to_rust(schema, out_dir, package_name="demodata",
                            serde_annotation=True, avro_annotation=True)

cargo build

Observed errors

error: implementation is not supported in `trait`s or `impl`s
   = note: this error originates in the macro `__lazy_static_internal`
           which comes from the expansion of the macro `lazy_static`
error[E0412]: cannot find type `SCHEMA` in this scope
error[E0422]: cannot find struct, variant or union type `SCHEMA` in this scope

The lazy_static! { pub static ref SCHEMA: Schema = ... } block appears to be emitted inside an impl/trait block (and/or references to SCHEMA are generated in scopes where the lazy_static-defined SCHEMA is not in scope) for enum/union types. A lazy_static! invocation is only valid at module scope, not inside impl/trait items.

For a single simple record the block is correctly emitted at module scope and compiles; the failure appears specific to enum/union type emission and/or multi-type crates.

Expected

The Avro-annotated Rust output compiles for enums, unions, and multi-type crates, with SCHEMA defined at module scope (or the Avro schema constant provided in a form valid inside impl blocks, e.g. a const/function instead of lazy_static!).

Impact / workaround

The xRegistry generator now passes avro_annotation=False for Rust so generated data crates always compile (Serde/JSON path). We'd like to re-enable Avro binary encoding for Rust once this is fixed.