oxiproto-codegen 0.1.2

Pure Rust protobuf code generator from FileDescriptorSet to Rust structs/enums
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

# oxiproto-codegen — `.proto` descriptor → plain-Rust source generator

[![Crates.io](https://img.shields.io/crates/v/oxiproto-codegen.svg)](https://crates.io/crates/oxiproto-codegen)
[![License](https://img.shields.io/badge/license-Apache--2.0-blue.svg)](LICENSE)

`oxiproto-codegen` is the **code-generation** stage of the **OxiProto** stack — COOLJAPAN's Pure-Rust Protocol Buffers implementation. It walks a `prost_types::FileDescriptorSet` and emits **plain Rust** `struct`s and `enum`s: no `prost` derive macros, no gRPC stubs by default, no validators. The result is ordinary Rust you can read, diff, and check in.

This crate is purely a string-in / string-out transform: it does not parse `.proto` files (that is `oxiproto-build`'s job, which produces the `FileDescriptorSet` this crate consumes). Optional features let it also emit native `OxiMessage`/`OxiName` impls, canonical Protobuf-JSON helpers, fluent builders, text-format printers, and run the output through `prettyplease`. The crate is `#![forbid(unsafe_code)]`.

## Installation

```toml
[dependencies]
oxiproto-codegen = "0.1.2"
```

With `rustfmt`-quality formatting of the generated source via `prettyplease`:

```toml
[dependencies]
oxiproto-codegen = { version = "0.1.2", features = ["format"] }
```

## Quick Start

Generate Rust source from a descriptor set (here produced by `oxiproto-build`):

```rust
use oxiproto_codegen::{generate, generate_with_options, CodegenOptions};

// `fds` is a prost_types::FileDescriptorSet, e.g. from
// oxiproto_build::compile_to_fds(&["proto/hello.proto"], &["proto/"])?
let fds = oxiproto_build::compile_to_fds(&["proto/hello.proto"], &["proto/"])?;

// Simplest path: defaults
let rust_src: String = generate(&fds)?;
println!("{rust_src}");

// With options: native impls + package modules + builders
let opts = CodegenOptions {
    emit_oxi_message_impl: true,
    package_namespacing: true,
    emit_builder: true,
    ..CodegenOptions::new()
};
let rust_src = generate_with_options(&fds, &opts)?;
# Ok::<(), Box<dyn std::error::Error>>(())
```

Preserve the package hierarchy as a structured tree instead of a flat string:

```rust
use oxiproto_codegen::{generate_module, CodegenOptions};

let tree = generate_module(&fds, &CodegenOptions::new())?;
for path in tree.all_paths() {
    println!("module: {}", path.join("::"));
}
let flat: String = tree.render(); // wrap each package in `pub mod { … }`
# Ok::<(), Box<dyn std::error::Error>>(())
```

## API Overview

### Top-level functions

| Function | Returns | Description |
|----------|---------|-------------|
| `generate(&fds)` | `Result<String, CodegenError>` | Generate Rust source with default options |
| `generate_with_options(&fds, &opts)` | `Result<String, CodegenError>` | Generate with custom `CodegenOptions`; runs `prettyplease` when `format_output` is set (requires `format`) |
| `generate_module(&fds, &opts)` | `Result<ModuleTree, CodegenError>` | Generate a structured `ModuleTree` preserving the package hierarchy |
| `generate_to_file(&fds, path)` | `Result<(), CodegenError>` | `generate` then write to `path` |
| `generate_to_file_with_options(&fds, path, &opts)` | `Result<(), CodegenError>` | `generate_with_options` then write to `path` |

### Lower-level emit functions

| Function | Description |
|----------|-------------|
| `emit_file_descriptor_set(&fds)` | Core emit with defaults (re-exported) |
| `emit_file_descriptor_set_with_options(&fds, &opts)` | Core emit with options (no `prettyplease` pass) |

### `CodegenOptions`

Construct with `CodegenOptions::new()` (or `Default`). Fields:

| Field | Type | Default | Description |
|-------|------|---------|-------------|
| `generate_docs` | `bool` | `true` | Emit doc comments from proto source info |
| `generate_default` | `bool` | `true` | Emit `Default` impls for enums |
| `generate_deprecated` | `bool` | `true` | Emit `#[deprecated]` on deprecated items |
| `btree_map` | `bool` | `false` | Use `BTreeMap` for map fields instead of `HashMap` |
| `use_btree_map` | `bool` | `false` | Backward-compat alias for `btree_map` |
| `package_namespacing` | `bool` | `false` | Emit `pub mod` hierarchy matching proto packages |
| `type_attributes` | `BTreeMap<String, Vec<String>>` | empty | Per-type extra attributes, keyed by FQN |
| `field_attributes` | `BTreeMap<String, Vec<String>>` | empty | Per-field extra attributes, keyed by `Type.field` |
| `emit_oxi_message_impl` | `bool` | `false` | Emit `impl OxiMessage`/`OxiName` (needs `oxiproto-core` downstream) |
| `format_output` | `bool` | `false` | Format output via `prettyplease` (needs `format` feature) |
| `emit_services` | `bool` | `true` | Emit `pub trait` service definitions |
| `emit_json` | `bool` | `false` | Emit `to_json`/`from_json` (needs `serde_json` + `base64` downstream) |
| `emit_builder` | `bool` | `false` | Emit a `FooBuilder` with fluent setters per message |
| `emit_text_format` | `bool` | `false` | Emit `to_text_format() -> String` per message |

Helper: `use_btree_map_effective()` → `btree_map || use_btree_map`.

### `ModuleTree`

Structured representation of generated code grouped by package. One node per package segment; the root has an empty `name`.

| Member | Type / Returns | Description |
|--------|----------------|-------------|
| `name` | `String` | One package segment (empty for the root) |
| `items` | `Vec<String>` | Rendered Rust items at this level (one entry per source file) |
| `children` | `Vec<ModuleTree>` | Sub-package nodes |
| `render()` | `String` | Flatten to source, wrapping each child in `pub mod { … }` |
| `all_paths()` | `Vec<Vec<String>>` | All module paths, depth-first |

### `wkt_map` module

| Function | Description |
|----------|-------------|
| `wkt_rust_type(proto_fqn) -> Option<&'static str>` | Map a well-known-type FQN (e.g. `google.protobuf.Timestamp`, leading dot optional) to its Rust path (e.g. `::oxiproto_wkt::Timestamp`); `None` if unknown |

## Feature Flags

| Feature | Default | Description |
|---------|---------|-------------|
| `format` | no | Pulls in `syn` + `prettyplease`; enables `CodegenError::Parse` and `format_output` handling in `generate_with_options` |

## Error Variants — `CodegenError`

Implements `Display` + `std::error::Error`. Round-trips to/from `oxiproto_core::OxiProtoError` via `From`.

| Variant | Description |
|---------|-------------|
| `InvalidDescriptor(String)` | A required descriptor field was missing or invalid |
| `Io(std::io::Error)` | An I/O operation failed (e.g. `generate_to_file`) |
| `Parse(syn::Error)` | A `syn`/`prettyplease` parse error (only with the `format` feature) |

## Related crates

- [`oxiproto`](../../README.md) — top-level façade that re-exports the OxiProto stack
- [`oxiproto-core`](../oxiproto-core) — runtime traits and wire-format primitives the generated code targets
- [`oxiproto-build`](../oxiproto-build) — produces the `FileDescriptorSet` this crate consumes (use in `build.rs`)
- [`oxiproto-cli`](../oxiproto-cli) — command-line front-end (`gen` subcommand drives this crate)
- `oxiproto-json` — canonical Protobuf-JSON support
- `oxiproto-reflect` — runtime reflection over descriptors
- `oxiproto-wkt` — Google well-known types (target of `wkt_map`)

## License

Apache-2.0 — COOLJAPAN OU (Team Kitasan)