import react from "@vitejs/plugin-react";
import reactCompiler from "babel-plugin-react-compiler";

// ONE React transform, shared by vite.config.ts and vitest.config.ts (E27 S1).
//
// It is a shared factory rather than two `react()` calls because the two configs must not drift:
// if the compiler ran only in the production build, every vitest run would be exercising code the
// user never receives, and a compiler-induced behaviour change would ship green. That is precisely
// the defect `0.93.2` was released to fix — a gate and a build image that had quietly stopped being
// the same thing — so the rule here is that the gate compiles the code the same way the build does.
//
// The React Compiler auto-memoises: it infers what `useCallback`/`useMemo` were being hand-written
// for and applies the equivalent itself. It is enabled repo-wide with no opt-out list because it
// bails out on its own for anything it cannot prove safe — SILENTLY: `panicThreshold` is "none" and
// there is no logger here, so a skipped component still works and simply re-renders everything under
// it. This comment used to say "its rules are also linted"; it was false while `react-hooks/refs` was
// off, and 95 functions sat uncompiled behind it (E32). What actually holds the line now is
// src/components/compilerCoverage.contract.test.ts, which runs THIS compiler over the shipped source
// and fails on any skip not on its list; the react-hooks lint rules are the early warning. None of
// them is off (three run at the preset's warn, which `--max-warnings 0` fails — docs/gates.md), but
// three of the compiler's diagnostics cannot report under the installed plugin (eslint.config.js
// says which), so the ratchet is the line, not the lint. `target` follows the installed React major and
// must move with it.
//
// The plugin is IMPORTED rather than named by the usual `"babel-plugin-react-compiler"` string. Two
// reasons, both about the gate: a string is invisible to knip, which then reports the dependency as
// unused, and — worse — a typo in that string is a silent no-op that ships an uncompiled bundle,
// while a bad import is a resolve error on the tsc lane.
//
// The price of the import: plugin-react finds the compiler only by that string, so it doesn't know the
// compiler is there. Its one compiler-specific switch is Babel's `retainLines`, which it turns on for
// dev (and so for vitest) unless the compiler is present. With the compiler's re-printed JSX that eats
// the space at the end of a text line ("for example <code>" rendered "for example/api/feed"). The
// production build never had it on. `generatorOpts` wins over the top-level option, so it is switched
// off here, for every mode. Pinned by src/jsxWhitespace.dom.test.tsx.
export const reactWithCompiler = () =>
  react({
    babel: {
      plugins: [[reactCompiler, { target: "19" }]],
      generatorOpts: { retainLines: false },
    },
  });