Use eslint to lint the eslint-config package itself

Signed-off-by: Émile Ré <emile@getprobo.com>

packages/eslint-config/src/baseConfigs.ts

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+import js from "@eslint/js";
+
+export const baseConfigs = [
+  { ignores: ["dist", "node_modules", "**/*.d.ts"] },
+  { files: ["**/*.js", "**/*.ts", "**/*.tsx"] },
+  js.configs.recommended,
+];

packages/eslint-config/src/index.ts

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+import { baseConfigs } from "./baseConfigs";
+import { browserLanguageOptionsConfig, nodeLanguageOptionsConfig } from "./languageOptionsConfigs";
+import { tsConfigs } from "./tsConfigs";
+import { reactConfigs } from "./reactConfigs";
+import { stylisticConfigs } from "./stylisticConfigs";
+
+export const configs = {
+  base: baseConfigs,
+  ts: tsConfigs,
+  languageOptions: {
+    browser: browserLanguageOptionsConfig,
+    node: nodeLanguageOptionsConfig,
+  },
+  react: reactConfigs,
+  stylistic: stylisticConfigs,
+};

packages/eslint-config/src/languageOptionsConfigs.ts

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+import * as globals from "globals";
+
+export const browserLanguageOptionsConfig = {
+  languageOptions: {
+    // Same as the ones we use in our tsconfig compilerOptions.lib for browser
+    ecmaVersion: 2022,
+    globals: {
+      ...globals.browser,
+      ...globals.es2022,
+    },
+    sourceType: "module",
+    parserOptions: {
+      projectService: true,
+      ecmaFeatures: {
+        impliedStrict: true,
+      },
+    },
+  },
+};
+
+export const nodeLanguageOptionsConfig = {
+  languageOptions: {
+    // Same as the ones we use in our tsconfig compilerOptions.lib for node
+    ecmaVersion: 2023,
+    globals: {
+      ...globals.node,
+      ...globals.es2023,
+    },
+    sourceType: "module",
+    parserOptions: {
+      projectService: true,
+      ecmaFeatures: {
+        impliedStrict: true,
+      },
+    },
+  },
+};

packages/eslint-config/src/reactConfigs.ts

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+import * as react from "eslint-plugin-react";
+import * as reactHooks from "eslint-plugin-react-hooks";
+
+export const reactConfigs = [
+  react.configs.flat.recommended,
+  react.configs.flat["jsx-runtime"],
+  reactHooks.configs.flat.recommended,
+];

packages/eslint-config/src/stylisticConfigs.ts

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+import stylistic from "@stylistic/eslint-plugin";
+import { type Linter } from "eslint";
+
+export const stylisticConfigs = [
+  stylistic.configs.customize({
+    arrowParens: false, // Will actually set it to "as-needed"
+    blockSpacing: true,
+    braceStyle: "1tbs",
+    commaDangle: "always-multiline",
+    indent: 2,
+    quotes: "double",
+    quoteProps: "consistent-as-needed",
+    semi: true,
+    jsx: true,
+    severity: "error",
+  }),
+  {
+    rules: {
+      "@stylistic/max-len": [
+        "warn",
+        { code: 120, ignoreUrls: true, ignoreStrings: true },
+      ],
+    },
+  } satisfies Linter.Config,
+];

packages/eslint-config/src/tsConfigs.ts

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+import { type Linter } from "eslint";
+import tseslint from "typescript-eslint";
+
+export const tsConfigs = [
+  ...tseslint.configs.recommendedTypeChecked,
+  {
+    files: ["**/*.{ts,tsx}"],
+    rules: {
+      "@typescript-eslint/no-unused-vars": [
+        "error",
+        {
+          args: "all",
+          argsIgnorePattern: "^_",
+          caughtErrors: "all",
+          caughtErrorsIgnorePattern: "^_",
+          destructuredArrayIgnorePattern: "^_",
+          varsIgnorePattern: "^_",
+          ignoreRestSiblings: true,
+        },
+      ],
+    },
+  } satisfies Linter.Config,
+];