Use select('#', ...) instead of ipairs on varargs

This means we don't discard any value after nil, meaning that
calls such as colors.combine(nil, 1, 2, 3) will error, rather
than returning 0.

src/main/resources/assets/computercraft/lua/rom/apis/colors.lua

@@ -20,8 +20,9 @@ black = 32768
 
 function combine( ... )
     local r = 0
-    for n,c in ipairs( { ... } ) do
-        expect(n, c, "number")
+    for i = 1, select('#', ...) do
+        local c = select(i, ...)
+        expect(i, c, "number")
         r = bit32.bor(r,c)
     end
     return r
@@ -30,8 +31,9 @@ end
 function subtract( colors, ... )
     expect(1, colors, "number")
     local r = colors
-    for n,c in ipairs( { ... } ) do
-        expect(n + 1, c, "number")
+    for i = 1, select('#', ...) do
+        local c = select(i, ...)
+        expect(i + 1, c, "number")
         r = bit32.band(r, bit32.bnot(c))
     end
     return r

src/main/resources/assets/computercraft/lua/rom/apis/textutils.lua

@@ -103,11 +103,9 @@ function pagedPrint( _sText, _nFreeLines )
 end
 
 local function tabulateCommon( bPaged, ... )
-    local tAll = { ... }
-    for k,v in ipairs( tAll ) do
-        if type( v ) ~= "number" and type( v ) ~= "table" then
-            error( "bad argument #"..k.." (expected number or table, got " .. type( v ) .. ")", 3 )
-        end
+    local tAll = table.pack(...)
+    for i = 1, tAll.n do
+        expect(i, tAll[i], "number", "table")
     end
 
     local w,h = term.getSize()
@@ -162,11 +160,11 @@ local function tabulateCommon( bPaged, ... )
 end
 
 function tabulate( ... )
-    tabulateCommon( false, ... )
+    return tabulateCommon( false, ... )
 end
 
 function pagedTabulate( ... )
-    tabulateCommon( true, ... )
+    return tabulateCommon( true, ... )
 end
 
 local g_tLuaKeywords = {

src/test/resources/test-rom/spec/apis/colors_spec.lua

@@ -1,9 +1,8 @@
 describe("The colors library", function()
     describe("colors.combine", function()
         it("validates arguments", function()
-            -- FIXME: Error when last argument is nil - use table.pack instead.
-            expect.error(colors.combine, 1, false):eq("bad argument #2 (expected number, got boolean)")
-            expect.error(colors.combine, 1, 1, false):eq("bad argument #3 (expected number, got boolean)")
+            expect.error(colors.combine, 1, nil):eq("bad argument #2 (expected number, got nil)")
+            expect.error(colors.combine, 1, 1, nil):eq("bad argument #3 (expected number, got nil)")
         end)
 
         it("combines colours", function()
@@ -15,8 +14,8 @@ describe("The colors library", function()
     describe("colors.subtract", function()
         it("validates arguments", function()
             expect.error(colors.subtract, nil):eq("bad argument #1 (expected number, got nil)")
-            expect.error(colors.subtract, 1, false):eq("bad argument #2 (expected number, got boolean)")
-            expect.error(colors.subtract, 1, 1, false):eq("bad argument #3 (expected number, got boolean)")
+            expect.error(colors.subtract, 1, nil):eq("bad argument #2 (expected number, got nil)")
+            expect.error(colors.subtract, 1, 1, nil):eq("bad argument #3 (expected number, got nil)")
         end)
 
         it("subtracts colours", function()

src/test/resources/test-rom/spec/apis/textutils_spec.lua

@@ -20,10 +20,36 @@ describe("The textutils library", function()
         end)
     end)
 
+    describe("textutils.tabulate", function()
+        it("validates arguments", function()
+            term.redirect(window.create(term.current(), 1, 1, 5, 5, false))
+
+            textutils.tabulate()
+            textutils.tabulate({ "test" })
+            textutils.tabulate(colors.white)
+
+            expect.error(textutils.tabulate, nil):eq("bad argument #1 (expected number or table, got nil)")
+            expect.error(textutils.tabulate, { "test" }, nil):eq("bad argument #2 (expected number or table, got nil)")
+        end)
+    end)
+
+    describe("textutils.pagedTabulate", function()
+        it("validates arguments", function()
+            term.redirect(window.create(term.current(), 1, 1, 5, 5, false))
+
+            textutils.pagedTabulate()
+            textutils.pagedTabulate({ "test" })
+            textutils.pagedTabulate(colors.white)
+
+            expect.error(textutils.pagedTabulate, nil):eq("bad argument #1 (expected number or table, got nil)")
+            expect.error(textutils.pagedTabulate, { "test" }, nil):eq("bad argument #2 (expected number or table, got nil)")
+        end)
+    end)
+
     describe("textutils.empty_json_array", function()
         it("is immutable", function()
             expect.error(function() textutils.empty_json_array[1] = true end)
-                :eq("textutils_spec.lua:25: attempt to mutate textutils.empty_json_array")
+                :eq("textutils_spec.lua:51: attempt to mutate textutils.empty_json_array")
         end)
     end)