Custom rules

You can define custom rules that can be enforced via the createRule function.

monoswan.config.ts

import { writeFile } from "node:fs/promises";
import { createRule, defineConfig } from "monoswan";

const requireDescription = createRule(() => ({
  name: "require-description",
  check: (context) =>
    context.packageJson.description == null
      ? [
          {
            message: "Expected a description",
            packageContext: context,
            filePath: `${context.packagePath}/package.json`,
            locator: { type: "json", locator: ["description"] },
            autofix: async ({ packageJson, packagePath }) => {
              const updated = { ...packageJson, description: "TODO" };
              await writeFile(
                `${packagePath}/package.json`,
                `${JSON.stringify(updated, null, "\t")}\n`,
              );
            },
          },
        ]
      : [],
}));

export default defineConfig({
  rules: [requireDescription()],
});

A rule receives packageName, packagePath, packageJson, and the resolved variant. Any other files may be loaded directly via node:fs APIs. Run monoswan lint --fix to apply returned autofixes.

Custom options

You can define custom options for consumers as part of the rule definition.

monoswan.config.ts

import { createRule, defineConfig } from "monoswan";

interface RequireFieldOptions {
  field: "description" | "license";
}

const requireField = createRule<RequireFieldOptions>(({ field }) => ({
  name: `require-${field}`,
  check: (context) =>
    context.packageJson[field] == null
      ? [
          {
            message: `Expected ${field}`,
            packageContext: context,
            filePath: `${context.packagePath}/package.json`,
            locator: { type: "json", locator: [field] },
          },
        ]
      : [],
}));

export default defineConfig({
  rules: [requireField({ field: "license" }, { ignore: { paths: ["examples/**"] } })],
});