feat(quarto): add quarto-lua skill for Lua shortcodes and filters

.claude-plugin/marketplace.json

@@ -74,7 +74,8 @@
       "skills": [
         "./brand-yml",
         "./quarto/quarto-authoring",
-        "./quarto/quarto-alt-text"
+        "./quarto/quarto-alt-text",
+        "./quarto/quarto-lua"
       ]
     }
   ]

README.md

@@ -54,6 +54,7 @@ Skills for Quarto document creation and publishing.
 - **[brand-yml](./brand-yml/)** - Create and apply brand.yml files for consistent styling across Quarto projects, supporting HTML documents, dashboards, RevealJS presentations, Typst PDFs, and websites with automatic brand discovery and theme layering
 - **[authoring](quarto/README.md#quarto-authoring-skill)** - Comprehensive guidance for Quarto document authoring and R Markdown migration. Write new Quarto documents with best practices, convert R Markdown files, migrate bookdown/blogdown/xaringan/distill projects, and use Quarto-specific features like hashpipe syntax, cross-references, callouts, and extensions
 - **[quarto-alt-text](./quarto/quarto-alt-text/)** - Generate accessible alt text for figures in Quarto documents using Amy Cesal's three-part formula (chart type, data description, key insight). Supports code-generated plots and static images
+- **[quarto-lua](./quarto/quarto-lua/)** - Write Lua shortcodes and filters for Quarto, with runtime access to Quarto's LLM-optimised API documentation
 
 ## Installation
 

quarto/README.md

@@ -76,10 +76,11 @@ Comprehensive guidance for Quarto document authoring and R Markdown migration. W
 Create and use `_brand.yml` files for consistent branding across Quarto documents and Shiny applications. Use when working with brand styling, corporate identity, colors, fonts, or logos in Quarto projects.
 
 **Organization**: Main skill file includes workflows and decision tree. Reference files provide framework-specific integration guides:
-- `brand-yml-spec.md` - Complete brand.yml specification
-- `shiny-r.md` - Shiny for R integration with bslib
-- `shiny-python.md` - Shiny for Python integration with ui.Theme
-- `quarto.md` - Quarto integration for all formats (HTML, dashboards, RevealJS presentations, Typst PDFs, websites)
+
+- `brand-yml-spec.md` - Complete brand.yml specification.
+- `shiny-r.md` - Shiny for R integration with bslib.
+- `shiny-python.md` - Shiny for Python integration with ui.Theme.
+- `quarto.md` - Quarto integration for all formats (HTML, dashboards, RevealJS presentations, Typst PDFs, websites).
 
 **Note**: This skill is also registered in the shiny category since brand.yml works across both Shiny and Quarto projects.
 
@@ -92,6 +93,16 @@ Create and use `_brand.yml` files for consistent branding across Quarto document
 
 ---
 
+### `lua`
+
+Write Lua shortcodes and filters for Quarto. Covers shortcode handlers, Pandoc AST filters, Lua coding conventions, Quarto-specific Lua APIs, and common patterns. Includes runtime access to Quarto's LLM-optimised documentation (`.llms.md` pages) for detailed API reference.
+
+#### Authors
+
+- [Mickaël CANOUIL](https://github.com/mcanouil)
+
+---
+
 ### `quarto-alt-text`
 
 Generate accessible alt text for data visualizations in Quarto documents. Use when adding, improving, or reviewing `fig-alt` for figures in `.qmd` files, or when making documents more accessible for screen readers.
@@ -106,13 +117,12 @@ Generate accessible alt text for data visualizations in Quarto documents. Use wh
 
 This category could include skills for:
 
-- Publishing workflows
-- Extension development
-- Template creation
-- Multi-format output
-- Parameterized reports
-- Website and book publishing
-- Presentation design
+- Publishing workflows.
+- Template creation.
+- Multi-format output.
+- Parameterized reports.
+- Website and book publishing.
+- Presentation design.
 
 ## Contributing
 

quarto/quarto-lua/SKILL.md

@@ -0,0 +1,181 @@
+---
+name: quarto-lua
+description: >
+  Write Lua shortcodes and filters for Quarto.
+  Use when creating, debugging, or modifying Lua code that runs inside
+  Quarto, including shortcode handlers, Quarto Lua filters, and
+  Quarto-specific Lua APIs.
+metadata:
+  author: Mickaël Canouil (@mcanouil)
+  version: "1.0"
+license: MIT
+---
+
+# Quarto Lua
+
+Write Lua shortcodes and filters for Quarto.
+
+> This skill is based on Quarto CLI v1.9.30 (2026-03-09).
+
+## When to Use What
+
+Task: Write a shortcode -> "Writing a Shortcode" below
+Task: Write a filter -> "Writing a Filter" below
+Task: Pandoc Lua API (constructors, types, methods) -> WebFetch `https://quarto.org/docs/extensions/lua-api.llms.md`
+Task: Debug Lua / tooling -> WebFetch `https://quarto.org/docs/extensions/lua.llms.md`
+Task: Shortcode details (args, raw output) -> WebFetch `https://quarto.org/docs/extensions/shortcodes.llms.md`
+Task: Filter details (AST traversal, multi-pass) -> WebFetch `https://quarto.org/docs/extensions/filters.llms.md`
+Task: Metadata / project filters -> WebFetch `https://quarto.org/docs/extensions/metadata.llms.md`
+Task: Custom AST nodes / filter timing -> Read `references/custom-ast-nodes.md` in this skill directory
+
+Fetch only pages relevant to the current task.
+
+## Writing a Shortcode
+
+A shortcode exports a function called whenever `{{< name ... >}}` appears in `.qmd`.
+Register under `shortcodes:` in `_extension.yml` or document YAML.
+Add a file header (see "Lua File Header Convention"), then:
+
+```lua
+return function(args, kwargs, meta, raw_args)
+  local name = pandoc.utils.stringify(args[1] or "world")
+  return pandoc.Str("Hello, " .. name .. "!")
+end
+```
+
+Parameters: `args` (positional, 1-indexed), `kwargs` (named), `meta` (document metadata), `raw_args` (unparsed strings).
+Both `args` and `kwargs` contain `pandoc.Inlines`; use `pandoc.utils.stringify()` to get strings.
+Return `pandoc.Inlines` or `pandoc.Blocks`. Use `pandoc.RawInline`/`pandoc.RawBlock` for format-specific output.
+Verify the exact handler signature against the shortcodes `.llms.md` page when targeting a specific Quarto version.
+
+## Writing a Filter
+
+A filter returns a list of handler tables mapping AST element types to transform functions.
+Register under `filters:` in `_extension.yml` or document YAML.
+Add a file header (see "Lua File Header Convention"), then:
+
+```lua
+local function convert_emph(el)
+  return pandoc.SmallCaps(el.content)
+end
+
+return {
+  { Emph = convert_emph }
+}
+```
+
+Each table is a separate traversal pass. Handlers return a replacement element, a list, or `nil` (or nothing) to skip.
+Use a `Pandoc(doc)` handler to process the entire document, or `Meta(meta)` to read/modify metadata.
+Multiple passes: `return { { Header = fix_headers }, { Link = fix_links } }`.
+
+## Lua File Header Convention
+
+Every `.lua` file must start with:
+
+```lua
+--- name - Short description
+--- @module name.lua
+--- @license MIT
+--- @copyright 2026 Author Name
+--- @author Author Name
+--- @version 0.1.0
+--- @brief One-line summary.
+--- @description Longer explanation of purpose and behaviour.
+---   Wrap at ~72 chars, indent continuation with two spaces.
+```
+
+Fields: `@module` (filename), `@license`, `@copyright`, `@author`, `@version` (semver), `@brief` (one-liner), `@description` (multi-line).
+Always generate for new files. Update `@version`/`@description` when modifying.
+
+## Lua Style and Conventions
+
+- **Naming**: `snake_case` for variables/functions, `PascalCase` for module-level tables only.
+- **Indentation**: 2 spaces.
+- **Strings**: double quotes for user-facing text, single quotes for identifiers/keys.
+- **Scoping**: always `local` unless intentionally global.
+- **Errors**: fail fast with `error("context: what went wrong")`.
+- **Docs**: `---` comment blocks above functions (LDoc-compatible):
+
+```lua
+--- Convert a Pandoc inline element to plain text.
+--- @param el pandoc.Inline The inline element to convert.
+--- @return string The plain text representation.
+local function stringify_inline(el)
+  return pandoc.utils.stringify(el)
+end
+```
+
+## Common Patterns
+
+### `pandoc.utils.stringify()`
+
+Converts any AST element to plain text. Use for shortcode arguments and metadata fields.
+
+### Format Detection
+
+Check the output format before emitting format-specific content:
+
+```lua
+if quarto.doc.is_format("html") then
+  -- HTML-only logic
+end
+```
+
+### Quarto Document APIs
+
+```lua
+-- HTML only; no-op for PDF/Typst
+quarto.doc.add_html_dependency({
+  name = "my-dep", version = "0.1.0",
+  stylesheets = { "style.css" }, scripts = { "script.js" }
+})
+
+-- Works for all formats (HTML, LaTeX/PDF, Typst)
+quarto.doc.include_text("in-header", "...")
+-- Positions: "in-header", "before-body", "after-body"
+```
+
+### Debugging
+
+```lua
+quarto.log.output("my-var:", my_var)
+```
+
+### Multi-file Modules
+
+```lua
+local utils = require("utils")
+```
+
+Quarto resolves `require` paths relative to the calling script's directory.
+
+### Testing
+
+```bash
+quarto render example.qmd
+```
+
+## Custom AST Nodes
+
+Quarto extends Pandoc's AST with custom node types that filters can match by name.
+
+**Block-level:** Callout, ConditionalBlock, Tabset, PanelLayout, FloatRefTarget, DecoratedCodeBlock, Theorem, Proof.
+
+**Inline-level:** Shortcode.
+
+**Other:** LatexEnvironment, LatexInlineCommand, HtmlTag.
+
+Constructors exist for: `quarto.Callout(tbl)`, `quarto.ConditionalBlock(tbl)`, `quarto.Tabset(tbl)`, `quarto.Tab(tbl)`.
+
+Cross-referenceable elements (figures, tables, listings) are represented as `FloatRefTarget` nodes.
+
+Filter timing supports eight phases (`pre-ast` through `post-finalize`) via the `at` property in `_extension.yml`.
+
+For full constructor signatures and filter timing details, read `references/custom-ast-nodes.md`.
+
+## Resources
+
+- [Quarto Lua API](https://quarto.org/docs/extensions/lua-api.html)
+- [Pandoc Lua Filters reference](https://pandoc.org/lua-filters.html)
+- [Pandoc community Lua filters](https://github.com/pandoc/lua-filters)
+- [LuaRocks style guide](https://github.com/luarocks/lua-style-guide)

quarto/quarto-lua/references/custom-ast-nodes.md

@@ -0,0 +1,84 @@
+# Custom AST Nodes
+
+Quarto extends Pandoc's AST with custom node types.
+Filters match these by name in handler tables (e.g., `{ Callout = handle_callout }`).
+
+## Available Node Types
+
+**Block-level:** Callout, ConditionalBlock, Tabset, PanelLayout, FloatRefTarget, DecoratedCodeBlock, Theorem, Proof.
+
+**Inline-level:** Shortcode.
+
+**Other:** LatexEnvironment, LatexInlineCommand, HtmlTag.
+
+Note: `_quarto.ast.add_handler()` is internal to Quarto.
+Extension authors interact via standard filter handlers.
+
+## Constructor Signatures
+
+### `quarto.Callout(tbl)`
+
+- `type`: `string` - callout type (note, caution, warning, tip, important).
+- `title`: `pandoc.Inlines` or `string` (optional).
+- `icon`: `boolean` or `string` (optional, defaults based on type).
+- `appearance`: `string` - "minimal", "simple", or "default" (optional).
+- `collapse`: collapse state (optional).
+- `content`: `pandoc.Blocks` or list (optional, defaults to empty Blocks).
+- `attr`: `pandoc.Attr` (optional, defaults to empty Attr).
+
+### `quarto.ConditionalBlock(tbl)`
+
+- `node`: `pandoc.Div` - the div holding the content.
+- `behavior`: `string` - "content-visible" or "content-hidden".
+- `condition`: list of 2-element lists (optional, defaults to `{}`).
+  Each sublist: `{"when-format"|"unless-format"|"when-profile"|"unless-profile", value}`.
+
+### `quarto.Tabset(tbl)`
+
+- `tabs`: list of `quarto.Tab` objects (optional, defaults to empty list).
+- `level`: `number` - heading level for tabs (optional, default `2`).
+- `attr`: `pandoc.Attr` (optional, defaults to `pandoc.Attr("", {"panel-tabset"})`).
+
+### `quarto.Tab(tbl)`
+
+- `title`: `pandoc.Inlines` or `string` (required).
+- `content`: `pandoc.Blocks` or `string` (optional, string parsed as markdown).
+- `active`: `boolean` (optional, default `false`).
+
+## Filter Timing
+
+Eight phases available via the `at` property in `_extension.yml` or document YAML:
+
+1. `pre-ast`
+2. `post-ast`
+3. `pre-quarto`
+4. `post-quarto`
+5. `pre-render`
+6. `post-render`
+7. `pre-finalize`
+8. `post-finalize`
+
+Syntax in `_extension.yml` or document YAML:
+
+```yaml
+filters:
+  - path: my-filter.lua
+    at: pre-quarto
+```
+
+Default (no `at`): filters listed before a "quarto" marker get `pre-quarto`, filters listed after get `post-render`.
+
+## FloatRefTarget
+
+Cross-referenceable elements (figures, tables, listings) are represented as `FloatRefTarget` custom AST nodes.
+Filters operating on these should use the `FloatRefTarget` handler:
+
+```lua
+return {
+  { FloatRefTarget = function(el)
+      -- el.caption, el.content, el.identifier, etc.
+      return el
+    end
+  }
+}
+```