bun-src/scripts/build/buildOptionsRs.ts

/**
 * Generates `${codegenDir}/build_options.rs` — Rust constants derived from
 * `Config`, `include!()`'d by `bun_core::build_options`.
 *
 * Replaces the `option_env!("BUN_*")` handshake (a dozen env vars exported
 * by `rust.ts`, read back in `bun_core`). `Config` is now the single source
 * of truth: literal `pub const`s land on disk, so a bare `cargo check` /
 * rust-analyzer sees the real version/sha/paths instead of placeholder
 * defaults, and the env-var name list isn't maintained in two places.
 *
 * `bun_core/build.rs` emits `rerun-if-changed` on the file; `writeIfChanged`
 * keeps the mtime stable so a reconfigure with the same sha doesn't
 * recompile `bun_core` and its dependents.
 *
 * Target-dependent constants (`ENABLE_TINYCC`, `ENABLE_ASAN`, `ENABLE_LOGS`)
 * stay as `cfg!()` expressions inside the generated file rather than literals
 * so a `cargo check --target <other-triple>` against the same generated file
 * still evaluates them per-target.
 *
 * Written at configure time alongside `depVersionsHeader.ts` /
 * `cargo-config.ts` — it's a constant manifest, not a build edge.
 */

import { mkdirSync } from "node:fs";
import { resolve } from "node:path";
import type { Config } from "./config.ts";
import { writeIfChanged } from "./fs.ts";

/** Rust string literal for `s`. JSON escaping is a strict subset of Rust's. */
const rstr = (s: string): string => JSON.stringify(s);
/**
 * Rust `&[u8]` literal for `s`. Goes via a UTF-8 string literal +
 * `.as_bytes()` rather than `b"..."` so non-ASCII paths (e.g. a Windows
 * checkout under `C:\Users\Müller\`) survive — Rust byte-string literals are
 * ASCII-only and `JSON.stringify` would pass the `ü` through verbatim.
 */
const rbstr = (s: string): string => `${JSON.stringify(s)}.as_bytes()`;

export function generateBuildOptionsRs(cfg: Config): string {
  const outPath = resolve(cfg.codegenDir, "build_options.rs");
  const [major, minor, patch] = cfg.version.split(".");

  const lines: string[] = [
    "// Generated by scripts/build/buildOptionsRs.ts from `Config` at configure",
    "// time. Do not edit. Regenerate with `bun bd`.",
    "",
    `pub const SHA: &str = ${rstr(cfg.revision)};`,
    `pub const REPORTED_NODEJS_VERSION: &str = ${rstr(cfg.nodejsVersion)};`,
    `pub const RELEASE_SAFE: bool = ${cfg.assertions};`,
    `pub const IS_CANARY: bool = ${cfg.canary};`,
    `pub const CANARY_REVISION: &str = ${rstr(cfg.canaryRevision)};`,
    `pub const ENABLE_FUZZILLI: bool = ${cfg.fuzzilli};`,
    `pub const FALLBACK_HTML_VERSION: &str = "0000000000000000";`,
    "pub const VERSION: crate::Version = crate::Version {",
    `    major: ${Number(major)},`,
    `    minor: ${Number(minor)},`,
    `    patch: ${Number(patch)},`,
    "};",
    `pub const BASE_PATH: &[u8] = ${rbstr(cfg.cwd)};`,
    `pub const CODEGEN_PATH: &[u8] = ${rbstr(cfg.codegenDir)};`,
    "",
    "// Target/profile-derived — kept as `cfg!()` so cross-target",
    "// `cargo check` evaluates per-triple. Values agree with `Config`:",
    "// rust.ts sets `--cfg=bun_debug` ⇔ `cfg.debug`, `--cfg=bun_asan` ⇔",
    "// `cfg.asan`, and `cfg.tinycc`'s default (config.ts) is the negation",
    "// of this predicate.",
    "pub const ENABLE_LOGS: bool = cfg!(bun_debug);",
    "pub const ENABLE_ASAN: bool = cfg!(bun_asan);",
    "pub const ENABLE_TINYCC: bool = !cfg!(any(",
    `    target_os = "android",`,
    `    target_os = "freebsd",`,
    "));",
    "",
  ];

  // Generated file self-opts-out of the workspace's denied unused lints. It is
  // `include!`d, where inner attributes are rejected, so tag each item.
  const allow = "#[allow(dead_code, unreachable_pub, unused)]";
  const withAllow = lines.flatMap(l => (l.startsWith("pub const ") ? [allow, l] : [l]));

  mkdirSync(cfg.codegenDir, { recursive: true });
  writeIfChanged(outPath, withAllow.join("\n"));
  return outPath;
}