Create Plugin

Overview

Use this skill for build-time Markdown and MDX transformations in this repo. Existing local plugins under gatsby/plugin/ show the expected pattern: transform markdownAST nodes, emit JSX when needed, then register the plugin in gatsby-config.js inside the gatsby-plugin-mdx pipeline.

Workflow

1) Confirm the task belongs in a Gatsby plugin

Use this skill when the request is about:

• Converting Markdown syntax into JSX or component tags
• Rewriting links, blockquotes, or code fences at build time
• Adding a local remark-like plugin under gatsby/plugin/

Prefer other skills when:

• Authors can already write <Component /> directly in MDX
• The change is only a React component or template change
• The change belongs in URL resolution or page creation

2) Pick the transformation layer

Inspect the current plugin chain in gatsby-config.js.

Current local MDX plugins:

• gatsby/plugin/mermaid
• gatsby/plugin/syntax-diagram
• gatsby/plugin/content

Decision rule:

• Transform Markdown AST nodes in gatsby/plugin/*/index.ts when source syntax should compile into JSX
• Update src/components/MDXComponents/* when the JSX tag already exists but the UI must change
• Touch both when the plugin emits a new custom tag like <Mermaid /> or <Note />

3) Implement the plugin

Create or update gatsby/plugin/<plugin-name>/index.ts.

Follow repo patterns:

• Use unist-util-visit for AST traversal
• Accept Gatsby MDX plugin input such as { markdownAST, markdownNode }
• Replace target nodes with { type: "jsx", value: "..." } when emitting component tags
• Use repo helpers instead of duplicating URL logic, for example:
  • gatsby/url-resolver
  • gatsby/link-resolver

If the plugin is new, also add gatsby/plugin/<plugin-name>/package.json matching the existing local plugin layout.

4) Register in Gatsby

Update gatsby-config.js.

For MDX pipeline work, register the plugin under gatsby-plugin-mdx -> gatsbyRemarkPlugins. Use require.resolve("./gatsby/plugin/<plugin-name>") to match current conventions.

Check whether plugin order matters:

• Link or content rewrites usually need deterministic ordering
• A later plugin will only see the AST shape produced by earlier plugins

5) Wire emitted JSX to runtime components when needed

If the plugin emits custom JSX tags, ensure the component exists in:

• src/components/MDXComponents/
• src/components/MDXComponents/index.tsx

In this repo, src/components/MDXContent.tsx already spreads ...MDXComponents into MDXProvider, so runtime registration is usually just the export in index.tsx.

6) Validate against representative content

At minimum:

• Verify the transformed node type and JSX string are valid
• Confirm any emitted component tag exists as a named export
• Review one representative Markdown or MDX example that exercises the plugin
• Run yarn build when feasible

Useful reference files:

• gatsby/plugin/content/index.ts
• gatsby/plugin/mermaid/index.ts
• gatsby/plugin/syntax-diagram/index.ts
• gatsby-config.js

Output Checklist

Report:

• Which plugin files changed or were added
• Where the plugin was registered in gatsby-config.js
• Whether a runtime MDX component was added or reused
• What sample Markdown syntax now works
• Whether yarn build was run