Type annotations for Pandoc Lua filters and custom writers/readers with Lua Language Server - LuaLS (VS code extension).

Just copy the pandoc-types-annotations.lua file among your sources, and write the following lines in your code:

---@module "pandoc-types-annotations"
local pandoc = pandoc ---@type pandoc

pandoc-types-annotations.lua contains no lua code, just comments used by LuaLS to provide you information about pandoc types.

The second line creates a local variable pointing to the global pandoc object.

The ---@type pandoc annotation is important to get help by LuaLS on pandoc modules and methods.

Creating a local variable has also the side effect of speeding up your code a bit, especially when you make frequent calls to pandoc. methods.

Some examples of annotations:

---@type Div
local div

local inline ---@type Inline

---A function to check if a Pandoc AST element has a class.
---@param element WithAttr An element with an Attr.
---@return boolean
local function hasClass(element)
  ...
end

LuaLS does not know about global data structures provided by pandoc.

So it complains with warnings like this:

Undefined global `pandoc`. Lua Diagnostics. (undefined-global)
(global) pandoc: unknown

The quick solutions LuaLS suggests is to add some configurations in the .vscode folder in the root of your project, or to add a line like these:

---@diagnostic disable: undefined-global
---@diagnostic disable-next-line: undefined-global

in your source file, whether you want to disable all the diagnostic warnings about undefined globals or just in the next line.

There's a better solution for globals provided by pandoc: just put the .luarc.json you find in this repo in the root directory of your project to prevent those LuaLS warnings, without the need to annotate your code with ---@diagnostic ... lines.

Here's its contents:

{
  "diagnostics.globals": [
    "FORMAT",
    "PANDOC_READER_OPTIONS",
    "PANDOC_WRITER_OPTIONS",
    "PANDOC_VERSION",
    "PANDOC_API_VERSION",
    "PANDOC_SCRIPT_FILE",
    "PANDOC_STATE",
    "pandoc",
    "lpeg",
    "re"
  ]
}