refactor(core)!: Move registerCommand() out of global to classes

BREAKING CHANGE: The role of document commands has always been tightly
scoped to classes. For example the *book* class has a `\footnote`
command while *plain* does not—unless you manually load the package and setup the
frames. In spite of this obvious functional scope, registering commands
has been a global operation that stored them in a global registry. In
order to allow SILE to be used more programmatically as a library with
potentially more than one document and class being processed at at once,
these need to be moved out of the global scope. This will also
facilitate things like being able *unload* packages and revert to
previous functionality for anything they over-rood on load. For now the
functionality is shimmed, but code using the `SILE.registerCommand()`
function should switch to the method of the same name on the current
class, i.e. `class:registerCommand()`.

classes/base.lua

@@ -181,6 +181,19 @@ function base:runHooks (category, args)
   end
 end
 
+function base.registerCommand (_, name, func, help, pack)
+  SILE.Commands[name] = func
+  if not pack then
+    local where = debug.getinfo(2).source
+    pack = where:match("(%w+).lua")
+  end
+  --if not help and not pack:match(".sil") then SU.error("Could not define command '"..name.."' (in package "..pack..") - no help text" ) end
+  SILE.Help[name] = {
+    description = help,
+    where = pack
+  }
+end
+
 function base:registerCommands ()
 
   local function replaceProcessBy(replacement, tree)

core/font.lua

@@ -57,7 +57,7 @@ SILE.registerCommand("font", function (options, content)
       lastshaper, SILE.shaper = nil, lastshaper
     end
   end
-end, "Set current font family, size, weight, style, variant, script, direction and language")
+end, "Set current font family, size, weight, style, variant, script, direction and language", nil, true)
 
 SILE.settings:declare({ parameter = "font.family", type = "string or nil", default = "Gentium Plus" })
 SILE.settings:declare({ parameter = "font.size", type = "number or integer", default = 10 })

core/hyphenator-liang.lua

@@ -164,4 +164,4 @@ SILE.registerCommand("hyphenator:add-exceptions", function (options, content)
       registerException(SILE._hyphenators[language], token.string)
     end
   end
-end)
+end, nil, nil, true)

core/languages.lua

@@ -47,7 +47,7 @@ SILE.registerCommand("language", function (options, content)
   else
     SILE.settings:set("document.language", main)
   end
-end)
+end, nil, nil, true)
 
 SILE.registerCommand("fluent", function (options, content)
   local key = content[1]
@@ -67,7 +67,7 @@ SILE.registerCommand("fluent", function (options, content)
     SU.warn(string.format("No localized message for %s found in locale %s", key, locale))
   end
   SILE.process({ message })
-end)
+end, nil, nil, true)
 
 SILE.registerCommand("ftl", function (options, content)
   local locale = options.locale or SILE.settings:get("document.language")
@@ -79,7 +79,7 @@ SILE.registerCommand("ftl", function (options, content)
     local input = content[1]
     fluent:add_messages(input, locale)
   end
-end)
+end, nil, nil, true)
 
 require("languages.unicode")
 

core/settings.lua

@@ -91,7 +91,7 @@ function settings:_init()
     else
       self:set(parameter, value, makedefault, reset)
     end
-  end, "Set a SILE parameter <parameter> to value <value> (restoring the value afterwards if <content> is provided)")
+  end, "Set a SILE parameter <parameter> to value <value> (restoring the value afterwards if <content> is provided)", nil, true)
 
 end
 

core/sile.lua

@@ -306,17 +306,17 @@ function SILE.call (command, options, content)
   return result
 end
 
-function SILE.registerCommand (name, func, help, pack)
-  SILE.Commands[name] = func
-  if not pack then
-    local where = debug.getinfo(2).source
-    pack = where:match("(%w+).lua")
+function SILE.registerCommand (name, func, help, pack, cheat)
+  if not cheat then
+    SU.deprecated("SILE.registerCommand", "class:registerCommand", "0.14.0", "0.16.0",
+    [[Commands are being scoped to the document classes they are loaded into rather than being globals.]])
+    local class = SILE.documentState.documentClass
+    if not class then SU.error("Can't register command "..name.." before a document class is loaded") end
+    class:registerCommand(name, func, help, pack)
+  else
+    -- Shimming until we have all scope cheating removed from core
+    SILE.classes.base.registerCommand(nil, name, func, help, pack)
   end
-  --if not help and not pack:match(".sil") then SU.error("Could not define command '"..name.."' (in package "..pack..") - no help text" ) end
-  SILE.Help[name] = {
-    description = help,
-    where = pack
-  }
 end
 
 function SILE.setCommandDefaults (command, defaults)