React Native Eslint: Enforce Platform Shared Types

enforce-platform-shared-types.js

const path = require("path");
const fs = require("fs");

module.exports = {
  meta: {
    type: "problem",
    docs: {
      description: "Enforce shared types for multi-platform components",
      category: "Possible Errors",
      recommended: true,
    },
    fixable: null,
  },
  create(context) {
    return {
      Program(node) {
        const filename = context.getFilename();
        const ext = path.extname(filename);
        const fullBasename = path.basename(filename, ext);
        const dirname = path.dirname(filename);

        if (!ext.endsWith("tsx")) {
          return;
        }

        // Remove platform-specific extension if present
        const basename = fullBasename.replace(
          /\.(native|web|ios|android)$/,
          ""
        );

        // Check for the existence of any variant (including the base file)
        const variants = [
          path.join(dirname, `${basename}.tsx`),
          ...platformExts.map((ext) => path.join(dirname, `${basename}${ext}`)),
        ];

        const existingVariants = variants.filter((v) => checkExists(v));
        const isMultiPlatform = existingVariants.length > 1;

        if (isMultiPlatform) {
          // Check if types file exists
          const typesFile = path.join(dirname, `${basename}.types.ts`);
          if (checkExists(typesFile)) {
            context.report({
              node,
              message: `Multi-platform component "${basename}" should have a separate types file "${basename}.types.ts"`,
            });
          } else {
            // Check if types are imported in the current file
            checkTypesImport(node, basename, context.report);
          }
        }
      },
    };
  },
};

// Platform extensions to check
const platformExts = [".native.tsx", ".web.tsx", ".ios.tsx", ".android.tsx"];

function checkTypesImport(node, basename, report) {
  const hasTypesImport = node.body.some(
    (n) =>
      n.type === "ImportDeclaration" && n.source.value === `./${basename}.types`
  );
  if (!hasTypesImport) {
    report({
      node,
      message: `Component "${basename}" should import types from "${basename}.types.ts"`,
    });
  }
}

const cache = new Map();
function checkExists(path) {
  if (cache.has(path)) {
    return cache.get(path);
  }

  const exists = fs.existsSync(path);
  cache.set(path, exists);
  return exists;
}