siftlode/frontend/eslint.config.js

import js from "@eslint/js";
import tseslint from "typescript-eslint";
import reactHooks from "eslint-plugin-react-hooks";
import reactRefresh from "eslint-plugin-react-refresh";
import prettier from "eslint-config-prettier";
import globals from "globals";

// Flat config (ESLint 9). Deliberately NARROW: the high-value rule here is
// react-hooks/exhaustive-deps — 33 suppressions across the app exist for it, and until this
// sprint nothing ran to make them mean anything. tsc already owns unused vars, undefined names
// and types (noUnusedLocals/Parameters + strict), so typescript-eslint's non-type-checked
// `recommended` is layered on but its overlap with tsc is turned off below to avoid double-reporting
// and a churny diff. `eslint-config-prettier` is LAST so formatting rules never fight Prettier.
//
// reportUnusedDisableDirectives: a `// eslint-disable` that no longer suppresses anything is itself
// an error — that is what keeps inert disable comments from re-accumulating (the S1b mandate).
export default tseslint.config(
  { ignores: ["dist", "node_modules", "playwright-report", "test-results", "e2e/.auth"] },
  {
    files: ["src/**/*.{ts,tsx}"],
    extends: [js.configs.recommended, ...tseslint.configs.recommended],
    languageOptions: {
      ecmaVersion: 2022,
      globals: { ...globals.browser },
    },
    plugins: {
      "react-hooks": reactHooks,
      "react-refresh": reactRefresh,
    },
    linterOptions: {
      reportUnusedDisableDirectives: "error",
    },
    rules: {
      ...reactHooks.configs.recommended.rules,
      "react-refresh/only-export-components": ["warn", { allowConstantExport: true }],
      // tsc already enforces these under strict + noUnusedLocals/Parameters — let it own them so a
      // finding is reported once, by one tool, and this config stays about hooks + refresh safety.
      "@typescript-eslint/no-unused-vars": "off",
      "no-undef": "off",
      // R7 S3a eliminated every explicit `any` (api.ts prefs/data bags → Record<string, unknown>;
      // catch clauses → unknown + HttpError narrowing; the YouTube IFrame boundary → lib/youtube.ts
      // types; i18n `t` props → TFunction), so the rule is now enforced to keep new ones from
      // creeping back in. Prefer `unknown` + narrowing, or a typed boundary, over `any`.
      "@typescript-eslint/no-explicit-any": "error",
      // Side-effect ternaries/short-circuits are an established idiom here (`cond ? a() : b()`,
      // `v.paused ? v.play() : v.pause()`) — allow them rather than rewrite working code to if/else.
      "@typescript-eslint/no-unused-expressions": [
        "error",
        { allowShortCircuit: true, allowTernary: true },
      ],
      // R10 S2: keep the rem system from rotting. A px-frozen `text-[Npx]` font size does NOT scale
      // with the Settings --font-scale slider while its rem neighbours do; use `text-2xs`/`text-3xs`
      // or a `text-[Nrem]` arbitrary instead. Matches both plain strings and template-literal chunks;
      // rem arbitraries (text-[0.75rem]) don't match (no "px"). Font-size `text-` only — not w-/h-/p-.
      "no-restricted-syntax": [
        "error",
        {
          selector: "Literal[value=/text-\\[\\d+px\\]/]",
          message:
            "px-frozen font size doesn't scale with --font-scale: use text-2xs/text-3xs or text-[Nrem], not text-[Npx] (R10 S2).",
        },
        {
          selector: "TemplateElement[value.raw=/text-\\[\\d+px\\]/]",
          message:
            "px-frozen font size doesn't scale with --font-scale: use text-2xs/text-3xs or text-[Nrem], not text-[Npx] (R10 S2).",
        },
      ],
    },
  },
  {
    // E10 S1: `components/ui/` is the PLATFORM layer, and the rule that makes it a layer rather than
    // a folder is enforced here, not in prose (see components/ui/README.md). A platform component is
    // domain-free: it may import sibling primitives and generic `lib/` helpers, never a feature
    // component (`../Feed`) and never a domain API slice. Without this rule the boundary erodes on
    // the first "just this once" import and the directory silently becomes another components/.
    files: ["src/components/ui/**/*.{ts,tsx}"],
    rules: {
      "no-restricted-imports": [
        "error",
        {
          // NOTE the String.raw: these are REGEX sources, and in a plain "..." literal `\.` is an
          // unknown escape that collapses to a bare `.` — the any-char wildcard. The first cut of
          // this rule shipped that way and matched far less than it read like (E10 review round 1).
          patterns: [
            {
              // `../X` (exactly one level up = a feature component). A `regex` rather than a glob:
              // eslint matches `patterns` gitignore-style, where `../*` also swallows `../../lib/x`.
              regex: String.raw`^\.\./(?!\.\./)`,
              message:
                "components/ui/ is domain-free: a platform component may not import a feature component. Invert the dependency (take a prop/render-prop) or keep the component outside ui/.",
            },
            {
              // The same file by its OTHER spelling. `../../components/Feed` resolves exactly where
              // `../Feed` does, so the rule above is only half the boundary; `ui/` is carved out
              // because a sibling primitive is the one thing this path may legitimately name.
              regex: String.raw`^\.\./\.\./components/(?!ui/)`,
              message:
                "components/ui/ is domain-free: a platform component may not import a feature component. Invert the dependency (take a prop/render-prop) or keep the component outside ui/.",
            },
            {
              // `(/|$)` so the BARREL counts too: `../../lib/api` is the spelling every feature
              // component uses, and a `/`-anchored pattern let exactly that one through.
              regex: String.raw`^\.\./\.\./lib/api(/|$)`,
              message:
                "components/ui/ is domain-free: a platform component may not call a domain API slice. Take the data as props.",
            },
          ],
        },
      ],
    },
  },
  {
    // E11 S3: the same one-way rule one layer down. `lib/` is what components are built ON (hooks,
    // the API slices, pure helpers), so it may not reach back UP into `components/` — not even for a
    // type. That is how the `Column` contract came to be owned by a ui component that three lib
    // helpers had to import from. A piece both layers need moves down into `lib/`.
    files: ["src/lib/**/*.{ts,tsx}"],
    rules: {
      "no-restricted-imports": [
        "error",
        {
          patterns: [
            {
              // Any depth (`lib/api/*` is one level deeper), and `(/|$)` so a bare barrel counts too.
              regex: String.raw`^(\.\./)+components(/|$)`,
              message:
                "lib/ sits below components/: it may not import from components/, not even a type. Move the shared piece down into lib/.",
            },
          ],
        },
      ],
    },
  },
  prettier,
);