This documentation language has been developed as part of LDT, its main goal is to describe the API supplied by a file. It is strongly inspired by LDoc. Information given with this language is parsed by LDT and supply advanced features such as code completion and documentation view. Before diving into syntax, it is time to enumerate the underlying concepts, knowing them will enable you to write documentation more efficiently.

Concepts

Our documentation language introduce some concepts which may not be described explicitly in Lua, but help to defined the contract between the library provider and the user.

Type

This is the most important one. A compound type is a set of values, accessible through fields. It is not a primitive type like string, number or nil. Theses fields can point to functions, primitive values or other compound types.

It is the way to explicitly ensure the structure of a Lua table.

Module

It is requireable entity - you can use the require function on it-
This concept allow you to express :

which type will be return by the require function for your module,
which new global variables will be available after your module was loaded.

Most of the time people refer to the returned type instance as module.

Field

It is always a field of a type. This is the way to ensure the presence of a value in a table which implement a type.

Function

It is a special kind of field which can have parameters and return values, just as Lua functions. Both parameters and returned values can be typed. This concept allow to express a contract about which parameters suit a function and expected outputs.

Global

When a module is required, it could modify the global environment. To handle those cases, the predefined type global is available. It is a reserved type which will be available everywhere, enabling you to attach field and function to it. This is a way to express the creation of new global variables when module is loaded.

global variable auto-completion behavior

To be aware of where a global variable is accessible is a real challenge for tooling. In fact, there two possibilities :

the global variable is preloaded by the interpreter (VM) at launch : in this case it's easy, the global variable is always accessible.
the global created dynamically at runtime : in this case, it's very difficult to know where the global variable must be available in autocompletion.

The first case (preloaded global var) is managed by the use of a global.lua file in execution environment which must contains all preloaded global variable. (those global vars will be always available in autocompletion)

The other case, LDT let you the choice between (togglable in Preference/Lua):

the default one, propose all global variables in project sourcepath/buildpath. (with the risk the global was not effectively available at runtime)
do not propose any global of this kind.

Type references

It is often needed to refer to a type. There is a notation for this. It is based on types. So if you want to type a field, a function parameter or returned value, they are several kinds of references available.

Primitive references

Refer to Lua primitive types, it is the type prefixed with #.

#boolean
#nil
#number
#string
#table

Internal references

Enables to refer to types defined in current module, it is type name prefixed with #.

#typename will refer to type typename defined in current module.

External references

Enables to refer to a type defined in another module, it is targeted module name followed by internal reference which could be used in targeted module.

modulename#typename will refer to type typename defined in module modulename.
modulename#modulename will refer to type modulename returned in module modulename.

Comments

You could describe explicitly all file API just with our documentation language. But LDT is able to guess quite a lot of this information from code. (see samples)

Special comments

First of all, only special comments are parsed as part of Lua documentation. To mark your comment as special, just start it with ---.

Special comments can contain a short and an long description. The short description start at the beginning of the comment and continue till . or ?. The long description is the text coming after. By the way, Markdown is supported in all descriptions.

Special comments are handled only if they describe a concept.

Note: All leading -'s in special comments are trimmed.

--------------------------------------------------------------------------------
-- Short description.
-- Long _markdown_ description

Special comment with trimmed first line

Note: _markdown_ is supposed to be interpreted by Markdown.

---
-- Short description.
-- Long description

Special comment composed of short comments format

--[[-
 Short description.
 Long description
]]

Special comment with long comment format

--- Short description. Long description

Special comment in one line

Type comment block

A type comment block is a special comment with a type declaration with @type key word followed by desired type name.

--------------------------------------------------------------------------------
-- Type short description.
-- Type long description
--
-- @type typename

Sample of type declaration

Module comment block

Denoted by @module keyword and followed by a module name, a module is the type described in a file. This is why there should be only one module declaration per file. Here is the simplest way to declare a module.

--------------------------------------------------------------------------------
-- Module short description.
-- Module long description
--
-- @module modulename

Sample of module declaration.

When a module is declared, a type with its name is automatically created and returned. So, the following is equivalent to first module sample.

--------------------------------------------------------------------------------
-- Module short description.
-- Module long description
--
-- @module modulename
-- @return #modulename
 
---@type modulename

Sample of verbose module declaration

Note: We used #modulename to refer to a declared type, if you want to know more about it refer to type reference section.

In previous sample, you may wonder in which case it could be of any use to return manually a type for a module. It is useful when you want to return a type different from the one automatically created.

--------------------------------------------------------------------------------
-- Module short description.
-- Module long description
--
-- @module modulename
-- @return #string

Sample of module returning custom type

Note: We used #string to refer to a primitive type.

Field comment block

The field block represents a field of a type. It is possible to declare one with @field keyword followed by optional type reference, field name and optional description.

There are two ways of defining a field, in its parent block type or in a separate documentation block where you have to mention field parent type.

--------------------------------------------------------------------------------
-- Type short description.
-- Type long description
--
-- @type typename
-- @field #string fieldname Field description

Sample of field declaration in parent type block

---
-- Type short description.
-- Type long description
--
-- @type typename
 
---
-- Field description
--
-- @field [parent=#typename] #string fieldname

Sample of field declaration in dedicated block

Function comment block

The function comment block has to be attached to a type. Its keyword is @function. A function can have several parameters denoted by keyword @param, they can be optionally typed with a type reference and have an optional descriptions. Several @return cases are also possible, but LDT inference -which is used for code assistance- only handles the first one. As Lua functions allow to return several values at once, it is possible to define several returned values per @return markup. Returned values can be optionally typed using a type reference.
Note: If the first @param is called self, LDT will show completion proposal without this parameter but using : invocation operator.

--------------------------------------------------------------------------------
-- Function short description.
-- Function long description
--
-- @function [parent=#typename] functionname
-- @param self Parameter description
-- @param #string parametername Parameter description
-- @return #number Typed return description
-- @return #nil, #string Traditional nil and error message
-- @return Untyped return description

Sample of function declaration

Note: It is also possible to document function for types which name contains ".".

--------------------------------------------------------------------------------
-- Function short description.
-- Function long description
--
-- @function [parent=#typeprefix.typename] functionname

Sample of function declaration related to a type which name contains "."

Global comment block

To declare a function or a field with a type reference as global, you just have to attach it to the global type.

--------------------------------------------------------------------------------
-- Field long description
--
-- @field [parent=#global] #string fieldname
 
--------------------------------------------------------------------------------
-- Function short description. Function long description
--
-- @function [parent=#global] functionname
-- @param self

Sample of global field and function

Samples

Simple module sample

---
-- Module short description.
-- Module _long description_
--
-- @module modulename
local M = {}
 
---
-- Field description
--
-- @field [parent=#modulename] #string fieldname 
M.fieldname = 'field value'
 
---
-- Function short description.
-- Function long description
--
-- @function [parent=#modulename] functionname
-- @param #number n Parameter description
-- @return #number Typed return description
-- @return #nil, #string Traditional nil and error message
function M.functionname(n)
  if n then return n else return nil, "error" end
end
return M

---
-- Module short description.
-- Module _long description_
local M = {}
 
---
-- Field description
M.fieldname = 'field value'
 
---
-- Function short description.
-- Function long description
-- @param #number n Parameter description
-- @return #number Typed return description
-- @return #nil, #string Traditional nil and error message
function M.functionname(n)
  if n then return n else return nil, "error" end
end
return M

---
-- Module short description.
-- Module _long description_
--
-- @module modulename
 
---
-- Field description
--
-- @field [parent=#modulename] #string fieldname 
 
---
-- Function short description.
-- Function long description
--
-- @function [parent=#modulename] functionname
-- @param #number n Parameter description
-- @return #number Typed return description
-- @return #nil, #string Traditional nil and error message
return nil

Full Documentation sample

Minimal Documentation

Documentation Only

Object-oriented sample

--- A module that allow to manage geometry shapes
-- @module geometry
local M = {}
 
--- A rectangle 
-- @type rectangle
-- @field #number x 
-- @field #number y 
-- @field #number width
-- @field #number height
local R = {x=0, y=0, width=100, height=100, }
 
--- Move the rectangle
-- @function [parent=#rectangle] move
-- @param self
-- @param x
-- @param y
function R.move(self,x,y)
  self.x = self.x + x
  self.y = self.y + y
end
 
--- Create a new rectangle
-- @function [parent=#geometry] newRectangle
-- @param x
-- @param y
-- @param width
-- @param height
-- @return #rectangle the created rectangle
function M.newRectangle(x,y,width,height)
  local newrectangle = {x=x,y=y,width=width,height=height}
 
  -- Set to new rectangle the properties of a rectangle
  setmetatable(newrectangle, {__index = R})
  return newrectangle
end
 
return M

--- A module that allow to manage geometry shapes
local M = {}
 
--- A rectangle 
-- @type rectangle
local R = {x=0, y=0, width=100, height=100, }
 
--- Move the rectangle
function R.move(self,x,y)
  self.x = self.x + x
  self.y = self.y + y
end
 
--- Create a new rectangle
-- @return #rectangle the created rectangle
function M.newRectangle(x,y,width,height)
  local newrectangle = {x=x,y=y,width=width,height=height}
 
  -- set to new rectangle the properties of a rectangle
  setmetatable(newrectangle, {__index = R})
  return newrectangle
end
 
return M

Full Documentation Sample

Minimal Documentation

Short references

It is way to reference a types and their fields in a textual description. You just have to surround a type reference with @{}. You can reference a types and their fields, functions are handled as a specific type of fields.

Reference to types
- @{#typename} will refer to type typename defined in current module.
- @{modulename} will refer to module named modulename.
- @{modulename#typename} will refer to type typename defined in module modulename.
Reference to fields
- @{#typename.fieldname} will refer to fieldname which could be a function or field attached to type typename defined in current module.
- @{modulename#typename.fieldname} will refer to fieldname which could be a function or field attached to type typename defined in modulename module.

Note: So far, there are no short references for globals.

--------------------------------------------------------------------------------
-- Short description. Long description with a reference to @{io#io.flush}.
--
-- @function [parent=#typename] functionname

Sample of type reference in a description

Ambiguity

It is possible to use dots in type names, but then it becomes hard to differentiate type name from field name. Let's explained the default behavior:

Everything before # is module name
Everything between # and last dot is type name.
Everything after last dot is field name

So in @{module.name#type.name.fieldname} will refer to field fieldname of type named type.name from module module.name. Well, but what happens when we simply want to reference a type name containing dots? It is possible to surround type name with parenthesis to remove ambiguity.

@{modulenamed#(type.name).fieldname} will refer to field named fieldname from type named type.name defined in module named modulename.
@{modulenamed#(type.name)} will refer to type named type.name from module named modulename
@{#(type.name)} will refer to type named type.name.

Limitations

Markdown

Markdown allows reusable element. As each description is parsed separately, you cannot reuse an element from another description.

Parsing

We use Metalua to parse comments, and it can't parse only comments. So if you write a documentation only file, ensure it contains a least a valid statement. Most of the time we use, return nil at end of file.

Tips

Usage

When you have a comment block related to a concept, you can give one or several samples of how it should be used by using the @usage keyword.

--------------------------------------------------------------------------------
-- Module short description.
-- Module long description
--
-- @module modulename
-- @usage local modulename = require 'modulename'
-- @usage require('modulename')

Sample of module declaration with usage markup.

LDT/User Area/Documentation Language

Contents

Concepts

Type

Module

Field

Function

Global

Type references

Primitive references

Internal references

External references

Comments

Special comments

Type comment block

Module comment block

Field comment block

Function comment block

Global comment block

Samples

Simple module sample

Object-oriented sample

Short references

Limitations

Markdown

Parsing

Tips

Usage

Breadcrumbs

LDT/User Area/Documentation Language

Contents

Concepts

Type

Module

Field

Function

Global

Type references

Primitive references

Internal references

External references

Comments

Special comments

Type comment block

Module comment block

Field comment block

Function comment block

Global comment block

Samples

Simple module sample

Object-oriented sample

Short references

Limitations

Markdown

Parsing

Tips

Usage