Recma-mdx-escape-missing-components NPM

recma-mdx-escape-missing-components

This package is a unified (recma) plugin to provide an opportunity for escaping mdx components which are missing or not provided in a MDX document.

unified is a project that transforms content with abstract syntax trees (ASTs) using the new parser micromark. recma adds support for producing a javascript code by transforming esast which stands for Ecma Script Abstract Syntax Tree (AST) that is used in production of compiled source for the MDX.

When should I use this?

This plugin is useful if you want to escape mdx components you did not provide in MDX.

You are not going to receive an error for missing or not provided mdx components since the recma-mdx-escape-missing-components sets the default value () => null for the mdx components.

Installation

This package is suitable for ESM only. In Node.js (version 16+), install with npm:

npm install recma-mdx-escape-missing-components

yarn add recma-mdx-escape-missing-components

Usage

Say we have the following file, example.mdx, which consists some mdx components.

# Hi

<Component1 />

<Component2 />

And our module, example.js, looks as follows:

import { read } from "to-vfile";
import { compile } from "@mdx-js/mdx";
import recmaMdxEscapeMissingComponents from "recma-mdx-escape-missing-components";

main();

async function main() {
  const source = await read("example.mdx");

  const compiledSource = await compile(source, {
    recmaPlugins: [recmaMdxEscapeMissingComponents],
  });

  return String(compiledSource);
}

Now, running node example.js produces the compiled source which contains the statement below:

// ...
const _EmptyComponent = () => null;
function _createMdxContent(props) {
  // ...
  const {Component1 = _EmptyComponent, Component2 = _EmptyComponent} = _components;
  // ...
}

Without the recma-mdx-escape-missing-components, you’d not get any Empty Component definition and default value for the components:

// ...
function _createMdxContent(props) {
  // ...
  const {Component1, Component2} = _components;
  // ...
}

Basically, the recma-mdx-escape-missing-components;

🟩 inserts an Empty Component definition into the code above the function _createMdxContent(props){}

const _EmptyComponent = () => null;

🟩 looks for a declaration statement in an object pattern initiated by the _components

const {Component1, Component2} = _components;

🟩 converts it as the destructed components have a default value _EmptyComponent

const {Component1 = _EmptyComponent, Component2 = _EmptyComponent} = _components;

Options

type TestFunction = (componentName: string) => boolean | undefined | null;

function recmaMdxEscapeMissingComponents(test?: string | string[] | TestFunction)

`test`

if "undefined", all components pass the check.
if "string", check the component name matches with the string.
if "string[]", check the component name is included in the string array.
if "TestFunction", check the test function returns true.
if check is true/pass, set the default value () => null for that component.

Examples:

# Hi

<Component1 />

Wellcome

<Component2 />

Without the `test` option

use(recmaMdxEscapeMissingComponents);

is going to produce the compiled source has the statement for all components have the default value:

const {Component1 = _EmptyComponent, Component2 = _EmptyComponent} = _components;

With the `test` option (string)

use(recmaMdxEscapeMissingComponents, "Component1");

is going to produce the compiled source has the statement for only the Component1 has the default value:

const {Component1 = _EmptyComponent, Component2} = _components;

With the `test` option (string array)

use(recmaMdxEscapeMissingComponents, ["Component1"]);

is going to produce the compiled source has the statement for only the Component1 has the default value:

const {Component1 = _EmptyComponent, Component2} = _components;

With the `test` option (function)

use(recmaMdxEscapeMissingComponents, ((name) => name.endsWith("2")) as TestFunction);

is going to produce the compiled source has the statement for only the Component2 has the default value:

const {Component1, Component2 = _EmptyComponent} = _components;

Syntax tree

This plugin only modifies the ESAST (Ecma Script Abstract Syntax Tree) as explained.

Types

This package is fully typed with TypeScript. Test function in the option is exported as type TestFunction.

Compatibility

This plugin works with unified version 6+. It is compatible with mdx version 3+.

Security

Use of recma-mdx-escape-missing-components doesn't involve user content so there are no openings for cross-site scripting (XSS) attacks.

My Plugins

I like to contribute the Unified / Remark / MDX ecosystem, so I recommend you to have a look my plugins.

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My Rehype Plugins

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My Recma Plugins

recma-mdx-escape-missing-components – Recma plugin to set the default value () => null for the Components in MDX in case of missing or not provided so as not to throw an error
recma-mdx-change-props – Recma plugin to change the props parameter into the _props in the function _createMdxContent(props) {/* */} in the compiled source in order to be able to use {props.foo} like expressions. It is useful for the next-mdx-remote or next-mdx-remote-client users in nextjs applications.