Add options component

Author: coatless

_extensions/options/_extension.yml

@@ -0,0 +1,8 @@
+name: options
+title: Developer extension to work with option data
+author: James Joseph Balamuta
+version: 0.0.0-dev.1
+quarto-required: ">=1.4.549"
+contributes:
+  filters:
+    - options.lua

_extensions/options/options.lua

@@ -0,0 +1,38 @@
+-- Check if variable missing or an empty string
+local function isVariableEmpty(s)
+  return s == nil or s == ''
+end
+
+-- Check if variable is present
+local function isVariablePopulated(s)
+  return not isVariableEmpty(s)
+end
+
+-- Check whether an argument is present in kwargs
+-- If it is, return the value
+local function tryOption(options, key)
+
+  -- Protect against an empty options
+  if not (options and options[key]) then
+      return nil
+  end
+
+  -- Retrieve the option
+  local option_value = pandoc.utils.stringify(options[key])
+  -- Verify the option's value exists, return value otherwise nil.
+  if isVariablePopulated(option_value) then
+      return option_value
+  else
+      return nil
+  end
+end
+
+-- Retrieve the option value or use the default value
+local function getOption(options, key, default)
+  return tryOption(options, key) or default
+end
+
+return {
+  ['tryOption'] = tryOption,
+  ['getOption'] = getOption
+}