refactor(core): Promote Lua input detection to first class

core/sile.lua

@@ -105,6 +105,8 @@ SILE.baseClass = setmetatable({}, {
     __index = nobaseclass
   })
 
+local defaultinputters = { "xml", "lua", "sil" }
+
 SILE.init = function ()
   -- Set by def
   if not SILE.backend then
@@ -134,10 +136,6 @@ SILE.init = function ()
     local _, err = pcall(func)
     if err then error(err) end
   end
-  -- Preload default reader types so content detection has something to work with
-  for _, inputter in ipairs({ "sil", "xml" }) do
-    local _ = SILE.inputters[inputter]
-  end
 end
 
 SILE.require = function (dependency, pathprefix, deprecation_ack)
@@ -196,6 +194,10 @@ SILE.process = function (input)
 end
 
 function SILE.readFile (filename)
+  -- Preload default reader types so content detection has something to work with
+  for _, inputter in ipairs(defaultinputters) do
+    local _ = SILE.inputters[inputter]
+  end
   SILE.currentlyProcessingFile = filename
   local doc
   if filename == "-" then
@@ -218,25 +220,27 @@ function SILE.readFile (filename)
       print("Could not open "..filename..": "..err)
       return
     end
-    io.stderr:write("<"..filename..">\n")
+    io.stderr:write("<"..filename..">")
     doc = file:read("*a")
   end
-  local sniff = doc:sub(1, 100):gsub("begin.*", "") or ""
   local contentDetectionOrder = {}
   for _, inputter in pairs(SILE.inputters) do
     if inputter.order then table.insert(contentDetectionOrder, inputter) end
   end
   table.sort(contentDetectionOrder, function (a, b) return a.order < b.order end)
   for _, inputter in ipairs(contentDetectionOrder) do
-    if inputter.appropriate(filename, sniff) then
-      SILE.inputter = inputter()
-      local pId = SILE.traceStack:pushDocument(filename, sniff, doc)
-      SILE.inputter:process(doc)
-      SILE.traceStack:pop(pId)
-      return
+    for round = 1, 3 do
+      if inputter.appropriate(round, filename, doc) then
+        io.stderr:write(" as " .. inputter._name .. "\n")
+        SILE.inputter = inputter()
+        local pId = SILE.traceStack:pushDocument(filename, doc)
+        SILE.inputter:process(doc)
+        SILE.traceStack:pop(pId)
+        return
+      end
     end
   end
-  SU.error("No input processor available for "..filename.." (should never happen)", true)
+  SU.error(("Unable to pick inputter to process input from '%s'"):format(filename))
 end
 
 -- Sort through possible places files could be

core/tracestack.lua

@@ -38,14 +38,14 @@ traceStack.defaultFrame = pl.class({
 
 traceStack.documentFrame = pl.class(traceStack.defaultFrame)
 
-function traceStack.documentFrame:_init (file, sniff)
+function traceStack.documentFrame:_init (file, snippet)
   self.command = "document"
   self.file = file
-  self.sniff = sniff
+  self.snippet = snippet
 end
 
 function traceStack.documentFrame:__tostring ()
-  return "<file> (" .. self.sniff .. ")"
+  return "<file> (" .. self.snippet .. ")"
 end
 
 traceStack.commandFrame = pl.class(traceStack.defaultFrame)
@@ -89,8 +89,9 @@ local function formatTraceLine (string)
 end
 
 -- Push a document processing run (input method) onto the stack
-function traceStack:pushDocument(file, sniff, _)
-  local frame = traceStack.documentFrame(file, sniff)
+function traceStack:pushDocument(file, doc)
+  local snippet = doc:sub(1, 100)
+  local frame = traceStack.documentFrame(file, snippet)
   return self:pushFrame(frame)
 end
 

inputters/lua.lua

@@ -0,0 +1,26 @@
+local base = require("inputters.base")
+
+local lua = pl.class(base)
+lua._name = "lua"
+
+lua.order = 99
+
+function lua.appropriate (round, filename, doc)
+  if round == 1 then
+    return filename:match("lua$")
+  elseif round == 2 then
+    local sniff = doc:sub(1, 100)
+    return sniff:match("^--") or sniff:match("^local") or sniff:match("^return")
+  elseif round == 3 then
+    local _, err = pcall(function () assert(load(doc)) end)
+    return not err
+  end
+end
+
+function lua:process (doc)
+  local root = SILE.documentState.documentClass == nil
+  local tree = load(doc)()
+  if root then self:classInit(tree) end
+end
+
+return lua

inputters/sil.lua

@@ -1,12 +1,25 @@
+local base = require("inputters.base")
+
 local lpeg = require("lpeg")
 local epnf = require("epnf")
 
-local base = require("inputters.base")
 local sil = pl.class(base)
 sil._name = "sil"
 
-sil.order = 99
-sil.appropriate = function () return true end
+sil.order = 50
+
+sil.appropriate = function (round, filename, doc)
+  if round == 1 then
+    return filename:match("sil$")
+  elseif round == 2 then
+    local sniff = doc:sub(1, 100)
+    return sniff:match("\\begin") or sniff:match("\\document")
+  elseif round == 3 then
+    local _parser = sil:rebuildParser()
+    local _, err = pcall(function () assert(epnf.parsestring(_parser, doc)) end)
+    return not err
+  end
+end
 
 local ID = lpeg.C(SILE.parserBits.letter * (SILE.parserBits.letter + SILE.parserBits.digit)^0)
 sil.identifier = (ID + lpeg.S":-")^1
@@ -189,8 +202,6 @@ function sil:process (doc)
       self:classInit(tree)
     end
     SILE.process(tree)
-  elseif not pcall(function () assert(load(doc))() end) then
-    SU.error("Input not recognized as Lua or SILE content")
   end
   if root and not SILE.preamble then
     SILE.documentState.documentClass:finish()

inputters/xml.lua

@@ -1,15 +1,25 @@
 local base = require("inputters.base")
+
+local lom = require("lomwithpos")
+
 local xml = pl.class(base)
 xml._name = "xml"
 
-xml.order = 1
+xml.order = 2
 
-function xml.appropriate (filename, sniff)
-  return filename:match("xml$") or sniff:match("<")
+function xml.appropriate (round, filename, doc)
+  if round == 1 then
+    return filename:match("xml$")
+  elseif round == 2 then
+    local sniff = doc:sub(1, 100):gsub("begin.*", "") or ""
+    return sniff:match("<")
+  elseif round == 3 then
+    local _, err = lom.parse(doc)
+    return not err
+  end
 end
 
 function xml:process (doc)
-  local lom = require("lomwithpos")
   local content, err = lom.parse(doc)
   if content == nil then
     error(err)