actual.js

const pure = () => <div />;
const pureProps = props => <div {...props} />;
const pureBlock = () => {
  return <div />;
};

const modulePatternClassic = () => ({
  render: function render() {
    return <div />; 
  }
});

const modulePatternModern = () => ({
  render() {
    return <div />;
    return;
  }
});

const arrowInObjectLiteral = () => ({
  render: () => <div />
});

const exportNamed = () => <div />;

export { exportNamed };

export default () => <div />;
export default () => {
  return <div />;
};

expected.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
var pure = "Direct JSX return statement";
var pureProps = "Direct JSX return statement";
var pureBlock = "Pure Block";

var modulePatternClassic = function modulePatternClassic() {
  return {
    render: function render() {
      return React.createElement("div", null);
    }
  };
};

var modulePatternModern = function modulePatternModern() {
  return {
    render: function render() {
      return React.createElement("div", null);
      return;
    }
  };
};

var arrowInObjectLiteral = function arrowInObjectLiteral() {
  return {
    render: function render() {
      return React.createElement("div", null);
    }
  };
};

var exportNamed = "Direct JSX return statement";

exports.exportNamed = exportNamed;
exports["default"] = "Export Default JSX Element";
exports["default"] = "Export Default Pure Block";

plugin.js

export default function ({Plugin, types: t}) {
  const formatters = new Map([
    ['VariableDeclarator', formatVariableDeclarator],
    ['ExportDefaultDeclaration', formatExportDefaultDeclaration]
  ]);
  
  function formatVariableDeclarator(node) {
    if (t.isJSXElement(node.body)) {
      return t.literal('Direct JSX return statement');
    }

    if (t.isBlockStatement(node.body)) {
      const [returnStatement] = node.body.body.filter(t.isReturnStatement);

      if (t.isJSXElement(returnStatement.argument)) {
        return t.literal('Pure Block'); 
      }
    }
  }
  
  function formatExportDefaultDeclaration(node) {
    if (t.isJSXElement(node.body)) {
      return t.literal('Export Default JSX Element'); 
    }

    if (t.isBlockStatement(node.body)) {
      const [returnStatement] = node.body.body.filter(t.isReturnStatement);

      if (t.isJSXElement(returnStatement.argument)) {
        return t.literal('Export Default Pure Block'); 
      }
    }
  }
  
  return new Plugin('ast-transform', {
    visitor: {
      ArrowFunctionExpression(node, parent) {
        if (formatters.has(parent.type)) {
          return formatters.get(parent.type)(node); 
        }
      }
    }
  });
}