no-mutable-exports.js

import docsUrl from '../docsUrl';

module.exports = {
  meta: {
    type: 'suggestion',
    docs: {
      url: docsUrl('no-mutable-exports'),
    },
    schema: [],
  },

  create(context) {
    function checkDeclaration(node) {
      const { kind } = node;
      if (kind === 'var' || kind === 'let') {
        context.report(node, `Exporting mutable '${kind}' binding, use 'const' instead.`);
      }
    }

    function checkDeclarationsInScope({ variables }, name) {
      for (const variable of variables) {
        if (variable.name === name) {
          for (const def of variable.defs) {
            if (def.type === 'Variable' && def.parent) {
              checkDeclaration(def.parent);
            }
          }
        }
      }
    }

    function handleExportDefault(node) {
      const scope = context.getScope();

      if (node.declaration.name) {
        checkDeclarationsInScope(scope, node.declaration.name);
      }
    }

    function handleExportNamed(node) {
      const scope = context.getScope();

      if (node.declaration)  {
        checkDeclaration(node.declaration);
      } else if (!node.source) {
        for (const specifier of node.specifiers) {
          checkDeclarationsInScope(scope, specifier.local.name);
        }
      }
    }

    return {
      'ExportDefaultDeclaration': handleExportDefault,
      'ExportNamedDeclaration': handleExportNamed,
    };
  },
};