Compiler Driven Development (CDD) is a development approach designed to eradicate the disconnect between: API specifications; server implementations; client SDKs; and command-line tooling.
Unlike traditional code generators—that treat outputs as disposable or read-only—CDD provides a complete, standalone compiler for each supported language. These compilers are fully CST-aware (Concreate Syntax Tree is a whitespace+comment aware Abstract Syntax Tree), allowing true bidirectional synchronization between existing hand-edited source code and OpenAPI specifications.
Traditional tools use naïve templating—if you regenerate, your custom code is overwritten.
The CDD ecosystem is fundamentally different. It utilizes language-specific, standalone compilers capable of full AST parsing, semantic diffing, and surgical patching.
The Core Guarantee: Every part of the generated codebase is fully editable. You are encouraged to open the generated routing files, model definitions, and CLI structures, and directly inject your business logic.
- When your specification changes, the CDD compiler reads your code, builds an AST, diffs it against the new spec, and safely patches in new endpoints or fields without touching your custom logic.
- When your codebase changes, the compiler reverse-engineers your structural updates back into a 100% accurate, authoritative OpenAPI specification.
flowchart TD
OAS["📄 OpenAPI v3 Spec"] <--> CDD{"⚙️ CDD Compiler"}
CDD <--> Codebase
subgraph Codebase ["💻 Application Codebase"]
direction TB
subgraph Outputs ["📦 Primary Outputs"]
direction TB
CLI["⌨️ CLI Tooling"]
SDK["📦 Client SDK"]
Server["🖥️ Server"]
%% Force vertical stacking inside the subgraph
CLI ~~~ SDK ~~~ Server
end
subgraph Core ["🔗 Core Architecture"]
direction TB
Models["🔗 Data Models"]
Routes["🔀 API Routes"]
Tests["🧪 Tests"]
%% Force vertical stacking inside the subgraph
Models ~~~ Routes ~~~ Tests
end
Mocks["🎭 API Mocks / Fakes"]
%% Simple dependency flow down the page
Outputs --> Core
Tests --> Mocks
end
style OAS fill:#e3f2fd,stroke:#1e88e5,stroke-width:2px
style CDD fill:#f3e5f5,stroke:#8e24aa,stroke-width:2px
style Codebase fill:#fafafa,stroke:#9e9e9e,stroke-width:2px,stroke-dasharray: 5 5
style Outputs fill:#e8f5e9,stroke:#43a047,stroke-width:2px
style Core fill:#fff3e0,stroke:#f57c00,stroke-width:2px
The CDD lifecycle supports continuous evolution from any starting point:
- Generate: Scaffold servers, SDKs, or CLIs from a central specification.
- Edit: Developers write real, unconstrained code directly in the generated files.
- Extract: Reverse-compile the edited code to produce an updated OpenAPI spec.
- Sync: Apply new specification changes seamlessly into the existing, hand-edited codebase.
Every supported language operates on the same core CDD philosophies but is powered by a dedicated, native compiler tailored to that language's specific AST, idioms, and package management.
All implementations share a standardized CLI interface (cdd [subcommand]), acting as a universal toolchain.
| Repository | Language | Client; Client CLI; Server | Extra features | Standards | CI Status |
|---|---|---|---|---|---|
cdd-c |
C (C89) | Client; Client CLI; Server | FFI | Swagger 2.0 & OpenAPI 3.2.0 |  |
cdd-cpp |
C++ | Client; Client CLI; Server | Upgrades Swagger & Google Discovery to OpenAPI 3.2.0 | Google Discovery; Swagger 2.0 & OpenAPI 3.2.0 |  |
cdd-csharp |
C# | Client; Client CLI; Server | CLR | Swagger 2.0 & OpenAPI 3.2.0 |  |
cdd-go |
Go | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-java |
Java | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-kotlin |
Kotlin (ktor for Multiplatform) | Client; Client CLI; Server | Auto-Admin UI | Swagger 2.0 & OpenAPI 3.2.0 |  |
cdd-php |
PHP | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-python |
Python | N/A (server building blocks) | CLI ↔ SQL ↔ Pydantic ↔ docs ↔ JSON-schema | N/A |  |
cdd-python-all |
Python | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-ruby |
Ruby | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 | |
|
cdd-rust |
Rust | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-sh |
Shell (/bin/sh) | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-swift |
Swift | Client; Client CLI; Server | Swagger 2.0 & OpenAPI 3.2.0 |  |
|
cdd-ts |
TypeScript | Client; Client CLI; Server | Auto-Admin UI; Angular; React; Vue; fetch; Axios; Node.js | Swagger 2.0 & OpenAPI 3.2.0 |  |
A true ecosystem requires standardized tooling. Once a developer learns the CDD toolchain, they can synchronize architecture across the entire polyglot stack.
--help: Print help information.--version: Print version information.--input, -i(or-f): Target file, directory, or OpenAPI spec.--output, -o: Destination path for generation or sync.
cdd-ruby from_openapi - Generate code from an OpenAPI specification.
Usage:
cdd-ruby from_openapi [target] [options]
Targets:
to_sdk_cli Generate a client SDK and a corresponding CLI.
to_sdk Generate a client SDK.
to_server Generate server boilerplate, models, and routing logic.
Options:
-i, --input <spec> Path to the OpenAPI specification file
-o, --output <dir> Destination path for generation (default: current directory)
--input-dir <dir> Directory of input specifications
--no-github-actions Disable GitHub Actions workflow generation
--no-installable-package Disable installable package generation
--tests Generate RSpec test scaffolding
--mcp Include Model Context Protocol support
--with-ephemeral Enable ephemeral code generation
--with-seed Include seed data in generation
-h, --help Show this help message
cdd-ruby to_openapi - Generate an OpenAPI specification from source code.
Usage:
cdd-ruby to_openapi -i <path/to/code> [-o <spec.json>]
Options:
-i, --input <path> Path to the source code directory or file to parse
-o, --output <path> Destination path for the generated OpenAPI spec (default: spec.json)
-h, --help Show this help message
cdd-ruby to_docs_json - Generate JSON documentation with code snippets for an OpenAPI specification.
Usage:
cdd-ruby to_docs_json [options] -i <spec.json> [-o <docs.json>]
Options:
-i, --input <spec> Path to the OpenAPI specification file
-o, --output <path> Destination path for the generated JSON docs (default: docs.json)
--no-imports Disable import statements in the generated documentation
--no-wrapping Disable line wrapping in the generated documentation
-h, --help Show this help message
cdd-ruby serve_json_rpc - Expose CLI interface as a JSON-RPC server.
Usage:
cdd-ruby serve_json_rpc [options]
Options:
-p, --port <port> Port to listen on (default: 8080)
-l, --listen <address> Address to bind to (default: 127.0.0.2)
-h, --help Show this help message
cdd-ruby mcp - Run the generator as an MCP server over stdio.
Usage:
cdd-ruby mcp [options]
Options:
-h, --help Show this help message
cdd-ruby sync - Synchronize an OpenAPI specification with source code.
Usage:
cdd-ruby sync [options] -i <filepath> --truth <class|activerecord|function>
Options:
-i, --input <filepath> Path to the input file
--truth <type> The source of truth for the synchronization (class, activerecord, function)
-h, --help Show this help message
The cdd-ruby CLI provides the following features beyond the common subset. Running cdd-ruby --help outputs:
cdd-ruby CLI
Usage:
cdd-ruby [subcommand] [options]
Subcommands:
from_openapi Generate code from an OpenAPI specification.
to_openapi Generate an OpenAPI specification from source code.
to_docs_json Generate JSON documentation with code snippets for an OpenAPI specification.
serve_json_rpc Expose CLI interface as a JSON-RPC server.
mcp Run the generator as an MCP server over stdio.
sync Synchronize an OpenAPI specification with source code.
Options:
-h, --help Show this help message
-v, --version Show version information
-p, --port <port> Port for the JSON-RPC server
-l, --listen <address> Host/IP to listen on for the JSON-RPC server
Examples:
cdd-ruby serve_json_rpc [--wasi] [-p <port>] [-l <listen>]
cdd-ruby from_openapi to_sdk_cli -i <spec.json> [-o <target_directory>] [--no-github-actions] [--no-installable-package] [--tests] [--mcp]
cdd-ruby from_openapi to_sdk -i <spec.json> [-o <target_directory>] [--no-github-actions] [--no-installable-package] [--tests] [--mcp]
cdd-ruby from_openapi to_server -i <spec.json> [-o <target_directory>]
cdd-ruby to_openapi -i <path/to/code> [-o <spec.json>]
cdd-ruby to_docs_json [--no-imports] [--no-wrapping] -i <spec.json> [-o <docs.json>]
Additionally, the following specific features are supported:
--testsflag support: Can generate RSpec test scaffolding when--testsis provided tofrom_openapi.--mcpflag support: Can include Model Context Protocol support when--mcpis provided tofrom_openapi.--no-github-actionsand--no-installable-package: Fine-grained control over generated SDK scaffolding.--with-ephemeraland--with-seed: Additional control overfrom_openapicode generation behavior.- Directory Input for
to_openapi: Allows scanning a directory structure of Ruby files to combine into a single OpenAPI specification.
With Compiler Driven Development, specifications and code are no longer loosely coupled artifacts. They are strict, isomorphic reflections of one another, maintained by dedicated standalone compilers.
Choose your language ecosystem above and start treating your architecture as a seamlessly compiled, endlessly editable whole.
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
