distributor/docs/integrations/markdown.md

# Markdown Integration

Audience: operators and maintainers who rely on generated HTML outputs from Markdown source files.

Markdown-to-HTML is an implemented file-format integration used by destination transform policy.

## Dependency

Rendering uses `github.com/yuin/goldmark`. The exact version is pinned in `go.mod`.

## Renderer Behavior

The transformer constructs `goldmark.New()` with no project-specific extensions, parser options, renderer options, templates, or source manifest metadata injection.

Supported output modes:

- `sidecar`: renders each source manifest file ending in `.md` and writes a generated output beside it with the `.md` suffix replaced by `.html`.
- `index`: renders one Markdown source file to `index.html` at the destination bundle path.

In `index` mode, `transform.markdown_to_html.input` may name the source manifest path to render. If `input` is omitted, the source manifest must list exactly one `.md` file. The selected input must be a clean relative source path, must be listed in the source manifest, and must end in `.md`.

When `transform.markdown_to_html.css_href` is set, generated HTML includes a stylesheet link in the document head. The href may be an absolute HTTP(S) URL, a root-relative path, or a relative URL path. Distributor treats this as a link reference only; it does not copy, publish, verify, or manage the CSS file solely because `css_href` is configured.

Raw HTML embedded in Markdown is not passed through by the current renderer behavior. Tests allow Goldmark's disabled-or-escaped raw HTML output forms and reject literal script tags in generated HTML.

## HTML Wrapper

Rendered Markdown body HTML is wrapped in a fixed document shell:

- `<!doctype html>`
- `<html lang="en">`
- UTF-8 `<meta charset>`
- optional `<link rel="stylesheet" href="...">` when `css_href` is configured
- empty `<title>`
- `<body>` containing the rendered Markdown body

The wrapper is deterministic. When `css_href` is omitted, the generated wrapper is unchanged from the unstyled output. When `css_href` is configured, its escaped link element is part of the generated output bytes.

## Output Metadata

Generated outputs record:

- destination path;
- source path;
- transform id `markdown_to_html`;
- SHA-256 digest of the wrapped HTML bytes;
- byte size of the wrapped HTML bytes.

Destination state stores generated outputs with `kind: generated`, `source_path`, `transform`, `sha256`, `size`, and optional `url`.

## Boundaries

Markdown rendering does not mutate source bundles, publish files, write `.distributor.json`, select destination actions, or choose catalog workflow behavior. Publish planning decides whether generated HTML is selected for a destination and destination state records the generated output metadata.

## Tests

Before changing Markdown renderer behavior, inspect and run:

```sh
go test ./internal/transform/markdown
```