@transferwise/eslint-plugin/rules/get-server-side-props-is-in-pages-directory.js

TransferWise ESLint plugin

/**
 * @fileoverview Ensures getServerSideProps is within the pages directory
 * @author fergusjordantw
 */

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = {
  meta: {
    docs: {
      description:
        "Declaring & exporting getServerSideProps outside of the Next page itself impedes Next's ability to strip code that is only used on server side",
      category: 'Best Practices',
      recommended: false,
    },
    fixable: null,
    schema: [],
  },

  create(context) {
    const sourceCode = context.sourceCode ?? context.getSourceCode();
    const filename = context.filename ?? context.getFilename();

    function checkExportedName(node) {
      const name = node?.name;

      if (name !== 'getServerSideProps') {
        return;
      }

      const isInPagesDirectory = filename.includes('pages');

      if (!isInPagesDirectory) {
        context.report({
          node,
          message:
            'getServerSideProps can only be exported from the pages directory',
        });
      }
    }

    function checkExportedNameFromNode(node) {
      const declaration = node.declaration;

      if (declaration) {
        if (
          declaration.type === 'FunctionDeclaration' ||
          declaration.type === 'ClassDeclaration'
        ) {
          checkExportedName(declaration.id);
        } else if (declaration.type === 'VariableDeclaration') {
          (sourceCode.getDeclaredVariables ? sourceCode.getDeclaredVariables(declaration, context) : context.getDeclaredVariables())
            .map((v) => v.defs.find((d) => d.parent === declaration))
            .map((d) => d.name)
            .forEach(checkExportedName);
        }
      } else {
        node.specifiers.map((s) => s.exported).forEach(checkExportedName);
      }
    }

    return {
      ExportAllDeclaration(node) {
        if (node.exported) {
          checkExportedName(node.exported);
        }
      },
      ExportNamedDeclaration: checkExportedNameFromNode,
      ExportDefaultDeclaration: checkExportedNameFromNode,
    };
  },
};