Make the Rustler generator usable from dependent projects, and restructure the docs by dannote · Pull Request #4 · open-pencil/kiwi_codec

dannote · 2026-10-23T17:01:14Z

The README said the Rustler generator compiles in development and test. That held only in this repository: a dependency compiles in production, so KiwiCodec.RustlerGenerator did not exist in projects using KiwiCodec, and Figler compiles our codegen/ itself to work around it.

RustQ is now an optional dependency, and each codegen module compiles only when RustQ is available. A project that adds RustQ in development and test gets the generator there and none in production. A new consumer test unpacks the package into a project like that, runs mix rustq.gen from its rustq.exs, checks the generated NIF, and compiles the project for production without RustQ.

Docs:

The README is rewritten in the style of the other READMEs; every example in it is checked against the code.
A Native decoders guide covers each generator feature, what it generates and returns, entrypoints, unknown fields, and the Decoder.
The generator architecture guide becomes Internals, for contributors, without the unverifiable Figler size numbers.
Module groups separate the public API from internals; RustlerGenerator.Decoder was missing from them.
mix docs has no warnings: specs use boolean() rather than R.bool(), and the Rust-only skip enum type is private.

The generated code builds with rustler 0.37, 0.38 (Figler), and 0.39 (the tests).

Summary by CodeRabbit

New Features
- Projects can use native decoder generation when the optional RustQ dependency is available, including in development and test builds.
- Added guidance for generating native decoders, defining and interpreting schemas, and handling fields unknown to generated modules.
Documentation
- Updated the README with installation, encoding and decoding examples, wire-format compatibility, and development requirements.
- Added and reorganized guides covering native decoders and project internals.
Bug Fixes
- Native decoders now continue decoding after encountering unknown fields.

…rewrite the README RustQ is an optional dependency, and every codegen module compiles only when RustQ is available, so a project adding RustQ in development and test gets the generator there and none in production. A consumer test generates through rustq.exs from the unpacked package. The README claimed the generator compiled in development and test, which was true only inside this repository, and asked to install once published. It now matches the other READMEs and says what the package does.

coderabbitai · 2026-10-23T17:01:26Z

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guides/native-decoders.md

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guides/native-decoders.md

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📝 Walkthrough

The Rustler generator modules are now defined only when RustQ is loadable. Consumer-package tests exercise Rust generation and production compilation. Package documentation now covers schema workflows, runtime decoding, containers, native decoders, and internals.

Changes: RustQ generator and consumer support

Layer / File(s)	Summary
Optional generator availability `mix.exs`, `codegen/kiwi_codec/rustler_generator.ex`, `codegen/kiwi_codec/rustler_generator/{decoder,decoder_macro,definition,entrypoint,selection,name}.ex`, `CHANGELOG.md`	Compilation paths include `codegen`, and RustQ is an optional dependency. Generator entry modules are defined only when RustQ is loadable.
Conditional decoder generation support `codegen/kiwi_codec/rustler_generator/{full,skip,sparse}/*`, `codegen/kiwi_codec/rustler_generator/{atom_cache,records,rust_expr,splice,unknown_fields}.ex`	Generator helper modules are conditional on RustQ. Several type declarations use `boolean()`. Sparse message decoding handles recognized and unknown field IDs until it reads `0`.
Consumer package generation and validation `integration/generator_consumer/`, `test/package/`	A consumer fixture configures RustQ to generate Node decoders. Package tests run generation, tests, and production compilation, while retaining runtime-only consumer coverage.
Package guides and documentation structure `README.md`, `CHANGELOG.md`, `lib/kiwi_codec.ex`, `guides/*`, `mix.exs`	The package documentation describes schema workflows, runtime decoding, containers, and native decoder generation. The native decoder and internals guides are added, and documentation groups are reorganized.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant PackageTest
  participant GeneratorConsumer
  participant RustQ
  participant KiwiCodec.RustlerGenerator
  PackageTest->>GeneratorConsumer: Copy fixture and set package path
  PackageTest->>GeneratorConsumer: Fetch dependencies and run rustq.gen
  GeneratorConsumer->>RustQ: Load configuration and generate decoders
  RustQ->>KiwiCodec.RustlerGenerator: Request source for Node entrypoint
  KiwiCodec.RustlerGenerator-->>RustQ: Return generated Rust source
  RustQ-->>GeneratorConsumer: Write native/src/generated.rs
  PackageTest->>GeneratorConsumer: Run tests and production compilation

Possibly related PRs

open-pencil/kiwi_codec#1: Adds native records, runtime-schema unknown-field handling, and Rustler generator modules that this change makes available to dependent projects and tests in consumer builds.
open-pencil/kiwi_codec#2: Defines the reference Decoder source and generated Rust build contract exercised by the consumer-package test.

Merge Risk: 🟡 Moderate · up to d503d

Readers cannot install the package using the README example. Correct the version before merging unless a compatible release is published.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely summarizes both primary changes: enabling dependent projects to use the Rustler generator and restructuring the documentation.
Docstring Coverage		Docstring coverage is 85.37% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 41 functions across 27 files. (1 skipped: 1…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 85.37% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 41 functions across 27 files. (1 skipped: 1 unsupported.)

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…d public modules apart from internals

dannote · 2026-10-23T17:16:04Z

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coderabbitai · 2026-10-23T17:16:10Z

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Actionable comments posted: 2

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Inline comments:
Review comments at @guides/native-decoders.md:
- Line 93: Update the setup example in the guide to enable sparse generation
with both the full and sparse features before the NIF example that calls
decode_sparse_node_from_decoder, or explicitly state that sparse generation must
be enabled before using that example.

Review comments at @README.md:
- Line 34: Update the `kiwi_codec` dependency version shown in the README to a
version published on Hex and consistent with this branch, so readers can resolve
it with `mix deps.get`; do not document version 0.5.0 until it is available.

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CHANGELOG.md
README.md
codegen/kiwi_codec/rustler_generator.ex
codegen/kiwi_codec/rustler_generator/atom_cache.ex
codegen/kiwi_codec/rustler_generator/decoder.ex
codegen/kiwi_codec/rustler_generator/decoder_macro.ex
codegen/kiwi_codec/rustler_generator/definition.ex
codegen/kiwi_codec/rustler_generator/entrypoint.ex
codegen/kiwi_codec/rustler_generator/full/helpers.ex
codegen/kiwi_codec/rustler_generator/name.ex
codegen/kiwi_codec/rustler_generator/records.ex
codegen/kiwi_codec/rustler_generator/rust_expr.ex
codegen/kiwi_codec/rustler_generator/selection.ex
codegen/kiwi_codec/rustler_generator/skip.ex
codegen/kiwi_codec/rustler_generator/skip/descriptor.ex
codegen/kiwi_codec/rustler_generator/skip/helpers.ex
codegen/kiwi_codec/rustler_generator/skip/value_helpers.ex
codegen/kiwi_codec/rustler_generator/sparse.ex
codegen/kiwi_codec/rustler_generator/sparse/helpers.ex
codegen/kiwi_codec/rustler_generator/splice.ex
codegen/kiwi_codec/rustler_generator/unknown_fields.ex
guides/internals.md
guides/native-decoders.md
integration/generator_consumer/mix.exs
integration/generator_consumer/rustq.exs
integration/generator_consumer/test/consumer_test.exs
integration/generator_consumer/test/test_helper.exs
lib/kiwi_codec.ex
mix.exs
test/package/consumer_test.exs
test/package/package_test.exs

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Restructure the docs: a Native decoders guide, an Internals guide, an…

a9d530f

…d public modules apart from internals

dannote changed the title ~~Make the Rustler generator usable from dependent projects, and rewrite the README~~ Make the Rustler generator usable from dependent projects, and restructure the docs Oct 23, 2026

coderabbitai Bot reviewed Oct 23, 2026

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Comment thread guides/native-decoders.md

Comment thread README.md

Name the feature the sparse NIF example needs

d503d53

dannote merged commit 97d1aa5 into master Oct 24, 2026
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dannote deleted the generator-for-consumers branch October 24, 2026 13:11

coderabbitai Bot mentioned this pull request Oct 24, 2026

0.5.0 #3

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Make the Rustler generator usable from dependent projects, and restructure the docs - #4

Make the Rustler generator usable from dependent projects, and restructure the docs#4
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