Function parse_file_descriptor_set 

pub fn parse_file_descriptor_set(
    file_descriptor_set: &FileDescriptorSet,
) -> Result<CodeGenMetadata>

Parse a compiled protobuf FileDescriptorSet into CodeGenMetadata.

This is the first stage of the code-generation pipeline. It walks every message, enum, and service in the descriptor set and extracts the annotations that drive generation (google.api.http, google.api.resource, field_behavior, debug_redact, …) into a structured form.

The full pipeline is three stages:

FileDescriptorSet
  │  parse_file_descriptor_set
  ▼
CodeGenMetadata
  │  analyze_metadata          (analysis/mod.rs)
  ▼
GenerationPlan
  │  generate_code             (codegen/mod.rs)
  ▼
Rust / Python / TypeScript source written to disk

Typical usage from a build script:

let fds = prost_types::FileDescriptorSet::decode(&bytes[..])?;
let metadata = parse_file_descriptor_set(&fds)?;
let config = CodeGenConfig::new(/* … */);
generate_code(&metadata, &config)?;

Returns an error if a descriptor contains an annotation that cannot be decoded; methods without HTTP annotations are not an error here (they are recorded later, during analyze_metadata).