# build/ — Bazel Build Rules

## OVERVIEW

Custom Bazel rules (`wd_*` macros) for C++, TypeScript, Rust, Cap'n Proto, and test orchestration. Uses bzlmod (`MODULE.bazel`), not WORKSPACE. This is build system definitions, NOT build output (`bazel-bin/`).

## KEY RULES

| Rule                                       | Purpose                                                                                           |
| ------------------------------------------ | ------------------------------------------------------------------------------------------------- |
| `wd_cc_library.bzl`                        | Wraps `cc_library`; `strip_include_prefix="/src"`, arch-specific CPU flags (CRC32C)               |
| `wd_cc_binary.bzl`                         | Wraps `cc_binary`; macOS dead-strip linkopts; creates `_cross` alias for prebuilt arm64 binaries  |
| `wd_cc_embed.bzl`                          | Binary/text data -> C++ via C23 `#embed`; auto-detects text vs binary by extension                |
| `wd_cc_benchmark.bzl`                      | Google Benchmark wrapper; generates CSV report genrule                                            |
| `wd_test.bzl`                              | `.wd-test` config test runner; generates up to 3 variants per test                                |
| `kj_test.bzl`                              | C++ unit test wrapper; also generates test variants                                               |
| `wpt_test.bzl`                             | Web Platform Tests; generates JS runner + `.wd-test` config from WPT tree; delegates to `wd_test` |
| `wd_ts_bundle.bzl`                         | TypeScript compilation + JS bundle generation                                                     |
| `wd_js_bundle.bzl`                         | JS bundle -> Cap'n Proto `Modules.Bundle` embedding via generated `.capnp`                        |
| `wd_capnp_library.bzl`                     | Cap'n Proto schema compilation                                                                    |
| `wd_rust_crate.bzl` / `wd_rust_binary.bzl` | Rust build rules                                                                                  |
| `lint_test.bzl`                            | ESLint integration                                                                                |

**Conventions:**

- `_cross` alias pattern: every `wd_cc_binary` gets a `name_cross` alias selecting prebuilt arm64 or source build
- Test tags: `off-by-default`, `requires-container-engine`, `no-asan`, `no-coverage`
- Variant generation controllable per-test via `generate_*_variant` booleans
- `BUILD.*` files: overlay build files for third-party deps (sqlite3, zlib, simdutf, pyodide, wpt)

## DEPENDENCY MANAGEMENT

Lives in `deps/`. Uses jsonc manifests + codegen:

- `deps.jsonc`, `build_deps.jsonc`, `shared_deps.jsonc` — dependency specifications
- `update-deps.py [dep_name]` — fetches latest versions, computes hashes, regenerates `gen/` MODULE.bazel fragments
- `gen/` — **autogenerated**; do not hand-edit
- `*.MODULE.bazel` (e.g., `rust.MODULE.bazel`, `v8.MODULE.bazel`) — included by root `MODULE.bazel`
- `workerd-v8/` — separate Bazel module wrapping V8 dependency
- `python/` — Pyodide package lists (versioned `.bzl` files)