# ⚙️ Bazel Adoption Evaluation for Ariane Monorepo

Date: 2025-09-17

Adopt once ≥2 of these become true:

1. WASM / Rust modules expand (e.g., multiple crates / shared libs)
2. Additional backend service(s) (e.g., gateway, API server) added
3. Test suite runtime > 8–10 minutes without caching
4. Frequent partial rebuild needs during PR iteration
5. Need reproducible SBOM / provenance chain for builds (supply chain compliance)

WORKSPACE.bazel
  ├─ rules_js, rules_rust, rules_python (if ever), platforms
  ├─ npm translation lock (via rules_js: pnpm / package.json import)
  └─ rust toolchain pinned

wasm/session-signer/BUILD.bazel
  rust_library(
    name = "signer_lib",
    srcs = ["src/lib.rs"],
    crate_features = ["wasm"],
  )

  # Custom rule or genrule to invoke wasm-bindgen/wasm-pack if needed:
  genrule(
    name = "signer_wasm",
    srcs = [":signer_lib"],
    outs = ["signer_bg.wasm", "signer.js"],
    cmd = "$(location //tools:wasm_pack) build --release --target web --out-dir $(RULEDIR) $(execpath :signer_lib)",
  )

tests/BUILD.bazel (later)
  nodejs_test(
    name = "unit_auth_tests",
    data = glob(["unit/**.test.ts"]),
    entry_point = "//tools:test_runner.js",
  )

NOTE: nodejs_test semantics differ depending on chosen ruleset. With modern rules_js, you’d define js_run_binary + harness script.

Astro’s dev server + HMR: keep outside Bazel for local iteration; only wrap production astro build for caching & dependency graph inclusion. Same pattern for sanity build.

1. bazel fetch //... (warm external repos)
2. bazel build //wasm/... //site:astro_build (selective subsets)
3. bazel test //tests:unit_auth_tests --test_output=errors
4. Fallback tasks (Lighthouse / Playwright) remain external until wrappers stable
5. Introduce bazelrc with common flags: --remote_cache=... (future), --experimental_remote_downloader=..., --repository_cache=...

Given current repository size and diversity, immediate Bazel adoption is optional and not critical to velocity. The highest leverage near-term engineering investment remains security/test breadth + automation gating (already being enhanced). Adopt Bazel later when build graph complexity or test duration starts to materially impact cycle time.

1. Create experimental/bazel/ branch
2. Add WORKSPACE.bazel + minimal wasm/session-signer/BUILD.bazel
3. Confirm bazel build //wasm/session-signer:signer_wasm reproduces wasm-pack output
4. Document steps in BAZEL_ADOPTION_LOG.md
5. Re-evaluate value after 2 weeks of trial

# WORKSPACE.bazel (excerpt)
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

# rules_rust
http_archive(
    name = "rules_rust",
    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.44.0/rules_rust-0.44.0.tar.gz"],
    sha256 = "<sha256_here>",
)
load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies")
rules_rust_dependencies()

# rules_js (example)
http_archive(
    name = "aspect_rules_js",
    urls = ["https://github.com/aspect-build/rules_js/releases/download/v2.0.0/rules_js-v2.0.0.tar.gz"],
    sha256 = "<sha256_here>",
)

# wasm/session-signer/BUILD.bazel (simplified)
load("@rules_rust//rust:defs.bzl", "rust_library")

rust_library(
    name = "signer_lib",
    srcs = glob(["src/**/*.rs"]),
    edition = "2021",
)

genrule(
    name = "signer_wasm",
    srcs = [":signer_lib"],
    outs = ["signer_bg.wasm"],
    cmd = "wasm-pack build --release --target web --out-dir $(@D)/out . && cp $(@D)/out/*wasm $@",
    tools = ["@npm//:wasm-pack"],  # or system dependency first pass
)

Adopt incrementally and experimentally; do not pause current testing/security roadmap for Bazel migration yet. Value can be re-assessed after codebase or team scale increases.

If you’d like, next step can be an experimental branch scaffold—just say the word and I can generate initial WORKSPACE + BUILD stubs (kept isolated).