pandoc.List.lua: make pandoc.List a callable constructor

It is now possible to construct a new List via `pandoc.List()` instead of
`pandoc.List:new()`.

data/pandoc.List.lua

@@ -1,28 +1,27 @@
 --[[
 List.lua
 
-Copyright © 2017–2018 Albert Krewinkel
+Copyright © 2017–2020 Albert Krewinkel
 
-Permission to use, copy, modify, and/or distribute this software for any purpose
+Permission to use, copy, modify, and/or distribute this software for any
-with or without fee is hereby granted, provided that the above copyright notice
+purpose with or without fee is hereby granted, provided that the above
-and this permission notice appear in all copies.
+copyright notice and this permission notice appear in all copies.
 
-THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
-FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
-TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-THIS SOFTWARE.
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. ]]
-]]
 
 --- Pandoc's List type and helper methods
 -- @classmod pandoc.List
 -- @author Albert Krewinkel
--- @copyright © 2017–2018 Albert Krewinkel
+-- @copyright © 2017–2020 Albert Krewinkel
 -- @license MIT
 local List = {
-  _VERSION = "0.1.0"
+  _VERSION = "1.0.0"
 }
 
 function List:new (o)
@@ -32,10 +31,6 @@ function List:new (o)
   return o
 end
 
-function List:__call (o)
-  return self:new(o)
-end
-
 --- Concatenates two lists.
 -- @param list second list concatenated to the first
 -- @return a new list containing all elements from list1 and list2
@@ -117,4 +112,11 @@ function List:filter (pred)
   return res
 end
 
+-- Set metatable with __call metamethod. This allows the use of `List`
+-- as a constructor function.
+local ListMT = {
+  __call = List.new
+}
+setmetatable(List, ListMT)
+
 return List

doc/lua-filters.md

@@ -2662,7 +2662,16 @@ Usage:
 
 # Module pandoc.List
 
-Pandoc\'s List type and helper methods
+The this module defines pandoc's list type. It comes with useful
+methods and convenience functions.
+
+## Constructor
+
+[`pandoc.List([table])`]{#pandoc.List}
+
+:   Create a new List. If the optional argument `table` is given,
+    set the metatable of that value to `pandoc.List`. This is an
+    alias for [`pandoc.List:new([table])`](#pandoc.list:new).
 
 ## Metamethods
 
@@ -2684,6 +2693,19 @@ Pandoc\'s List type and helper methods
 
 :   Returns a (shallow) copy of the list.
 
+[`pandoc.List:new([table])`]{#pandoc.List:new}
+
+:   Create a new List. If the optional argument `table` is given,
+    set the metatable of that value to `pandoc.List`.
+
+    Parameters:
+
+    `table`:
+    :   table which should be treatable as a list; defaults to an
+        empty table
+
+    Returns: the updated input value
+
 [`pandoc.List:includes (needle, init)`]{#pandoc.List:includes}
 
 :   Checks if the list has an item equal to the given needle.

test/lua/module/pandoc-list.lua

@@ -6,6 +6,15 @@ local test = tasty.test_case
 local group = tasty.test_group
 
 return {
+  group 'List as function' {
+    test('equivalent to List:new', function (x)
+      local new = List:new {'ramen'}
+      local list = List {'ramen'}
+      assert.are_same(new, list)
+      assert.are_equal(getmetatable(new), getmetatable(list))
+    end)
+  },
+
   group 'new' {
     test('make table usable as list', function ()
       local test = List:new{1, 1, 2, 3, 5}