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recma-mdx-change-imports

This package is a unified (recma) plugin that converts import declarations with relative path into variable declarations of string URLs for assets and media in the compiled MDX source.

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?

Use recma-mdx-change-imports to enable direct asset URL resolution in MDX documents.

recma-mdx-change-imports transforms relative paths into string URLs for asset/media imports, ensuring they are correctly resolved in the compiled MDX output.

It resolves asset relative paths using the provided pathname option.

Assume the option pathname is data/articles.

For example, it transforms:

import imgUrl from "./image.png";

into

const imgUrl = "/data/articles/image.png";

It supports ../ to resolve paths to parent and sibling directories. So it can transforms:

import imgUrl from "../blog-assets/image.png";

into

const imgUrl = "/data/blog-assets/image.png";

Using this plugin, you can write content in MDX like this:

import imgUrl from "./image.png";

<img src={imgUrl} alt="Example image" />

Otherwise, you probably get an error about unknown file extension .png.

[!WARNING]
@next/mdx users may not need to use recma-mdx-change-props since built-in bundler system in nextjs can resolve the assets properly.

Installation

This package is suitable for ESM only. In Node.js (version 18+), install with npm:

npm install recma-mdx-change-imports

or

yarn add recma-mdx-change-imports

Usage

Say we have the following file, example.mdx,

## Title

import imgUrl from "./image.png";

<img src={imgUrl} alt="Example image" />

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

import { read } from "to-vfile";
import { compile } from "@mdx-js/mdx";
import recmaMdxChangeImports from "recma-mdx-change-imports";

main();

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

  const compiledSource = await compile(source, {
    outputFormat: "function-body",
    recmaPlugins: [[recmaMdxChangeImports, {pathname: "data/articles"}]],
  });

  return String(compiledSource);
}

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

"use strict";
const {Fragment: _Fragment, jsx: _jsx, jsxs: _jsxs} = arguments[0];
const _importMetaUrl = arguments[0].baseUrl;
if (!_importMetaUrl) throw new Error("Unexpected missing \`options.baseUrl\` needed to support \`export … from\`, \`import\`, or \`import.meta.url\` when generating \`function-body\`");
- const {default: imgUrl} = await import(_resolveDynamicMdxSpecifier("./image.png"));
+ const imgUrl = "/data/articles/image.png";
function _createMdxContent(props) {
  const _components = {
    h2: "h2",
    ...props.components
  };
  return _jsxs(_Fragment, {
    children: [_jsx(_components.h2, {
      children: "Title"
    }), "\\n", "\\n", _jsx("img", {
      src: imgUrl,
      alt: "Example image"
    })]
  });
}
function MDXContent(props = {}) {
  const {wrapper: MDXLayout} = props.components || ({});
  return MDXLayout ? _jsx(MDXLayout, {
    ...props,
    children: _jsx(_createMdxContent, {
      ...props
    })
  }) : _createMdxContent(props);
}
return {
  default: MDXContent
};
function _resolveDynamicMdxSpecifier(d) {
  if (typeof d !== "string") return d;
  try {
    new URL(d);
    return d;
  } catch {}
  if (d.startsWith("/") || d.startsWith("./") || d.startsWith("../")) return new URL(d, _importMetaUrl).href;
  return d;
}

Options

All options are optional and have no default value which is undefined.

export type ChangeImportsOptions = {
  pathname?: string; // default is undefined
  baseUrl?: string; // default is undefined
};

pathname

It is a string option that serves as a base path for resolving relative paths, ultimately determining the final asset path as resolved path.

If no pathname is provided, the plugin simply removes ./ and ../ from the relative path without proper resolution. Therefore, it is recommended to always specify a pathname; otherwise, the plugin cannot determine the correct current, parent, or ancestor directories.

Similarly, if a pathname is provided but the resolved path exceeds the root, ./ and ../ are removed in the same way, preventing invalid path resolution.

use(recmaMdxChangeImports, {pathname: "data/articles"} as ChangeImportsOptions);

Let's assume we have the import statement import imgUrl from "./image.png" in an MDX file.

With the option pathname, now the statement in the compiled MDX source is going to be:

const imgUrl = "/data/articles/image.png";

baseUrl

It is a string option which is for resolving absolute path (file:///) produced by compilation of MDX.

recma-mdx-change-imports utilizes the baseUrl for deriving relative path from the absolute path, if necessary.

baseUrl should be the same with baseUrl in @mdx-js/mdx. In some cases, you may not need to provide a baseUrl, because the compile of @mdx-js/mdx may not produce absolute path according to the options provided. If you see the image doesn't display and the src property consists something ../file:///.. then you need to provide the same baseUrl (mostly import.meta.url) to the plugin.

use(recmaMdxChangeImports, {pathname: "data/articles", baseUrl: import.meta.url} as ChangeImportsOptions);

Syntax tree

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

Types

This package is fully typed with TypeScript. The plugin options is exported as ChangeImportsOptions.

Compatibility

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

Security

Use of recma-mdx-change-imports does not 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.

My Remark Plugins

• remark-flexible-code-titles – Remark plugin to add titles or/and containers for the code blocks with customizable properties
• remark-flexible-containers – Remark plugin to add custom containers with customizable properties in markdown
• remark-ins – Remark plugin to add ins element in markdown
• remark-flexible-paragraphs – Remark plugin to add custom paragraphs with customizable properties in markdown
• remark-flexible-markers – Remark plugin to add custom mark element with customizable properties in markdown
• remark-flexible-toc – Remark plugin to expose the table of contents via vfile.data or via an option reference
• remark-mdx-remove-esm – Remark plugin to remove import and/or export statements (mdxjsEsm)

My Rehype Plugins

• rehype-pre-language – Rehype plugin to add language information as a property to pre element
• rehype-highlight-code-lines – Rehype plugin to add line numbers to code blocks and allow highlighting of desired code lines
• rehype-code-meta – Rehype plugin to copy code.data.meta to code.properties.metastring
• rehype-image-toolkit – Rehype plugin to enhance Markdown image syntax ![]() and Markdown/MDX media elements (<img>, <audio>, <video>) by auto-linking bracketed or parenthesized image URLs, wrapping them in <figure> with optional captions, unwrapping images/videos/audio from paragraph, parsing directives in title for styling and adding attributes, and dynamically converting images into <video> or <audio> elements based on file extension.

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.
• recma-mdx-change-imports – Recma plugin to convert import declarations for assets and media with relative links into variable declarations with string URLs, enabling direct asset URL resolution in compiled MDX.
• recma-mdx-import-media – Recma plugin to turn media relative paths into import declarations for both markdown and html syntax in MDX.
• recma-mdx-import-react – Recma plugin to ensure getting React instance from the arguments and to make the runtime props {React, jsx, jsxs, jsxDev, Fragment} is available in the dynamically imported components in the compiled source of MDX.
• recma-mdx-html-override – Recma plugin to allow selected raw HTML elements to be overridden via MDX components.
• recma-mdx-interpolate – Recma plugin to enable interpolation of identifiers wrapped in curly braces within the alt, src, href, and title attributes of markdown link and image syntax in MDX.

License

MIT License © ipikuka