Delay instantiating all the formatter function classes

src/calibre/utils/formatter_functions.py

@@ -10,6 +10,7 @@ __docformat__ = 'restructuredtext en'
 
 import inspect, re, traceback
 from math import trunc
+from threading import RLock
 
 from calibre import human_readable
 from calibre.constants import DEBUG
@@ -25,6 +26,15 @@ class FormatterFunctions(object):
     def __init__(self):
         self._builtins = {}
         self._functions = {}
+        self._lock = RLock()
+        self._loaded = False
+
+    def load_builtins(self):
+        with self._lock:
+            if not self._loaded:
+                self._loaded = True
+                for c in _formatter_builtins:
+                    c()
 
     def register_builtin(self, func_class):
         if not isinstance(func_class, FormatterFunction):
@@ -39,6 +49,7 @@ class FormatterFunctions(object):
             self._functions[a] = func_class
 
     def register_function(self, func_class):
+        self.load_builtins()
         if not isinstance(func_class, FormatterFunction):
             raise ValueError('Class %s is not an instance of FormatterFunction'%(
                                     func_class.__class__.__name__))
@@ -48,9 +59,11 @@ class FormatterFunctions(object):
         self._functions[name] = func_class
 
     def get_builtins(self):
+        self.load_builtins()
         return self._builtins
 
     def get_builtins_and_aliases(self):
+        self.load_builtins()
         res = {}
         for f in self._builtins.itervalues():
             res[f.name] = f
@@ -59,10 +72,12 @@ class FormatterFunctions(object):
         return res
 
     def get_functions(self):
+        self.load_builtins()
         return self._functions
 
     def reset_to_builtins(self):
         self._functions = {}
+        self.load_builtins()
         for n,c in self._builtins.items():
             self._functions[n] = c
             for a in c.aliases:
@@ -1210,27 +1225,27 @@ class BuiltinFinishFormatting(BuiltinFormatterFunction):
         return prefix + formatter._do_format(val, fmt) + suffix
 
 _formatter_builtins = [
-    BuiltinAdd(), BuiltinAnd(), BuiltinApproximateFormats(),
-    BuiltinAssign(), BuiltinBooksize(),
-    BuiltinCapitalize(), BuiltinCmp(), BuiltinContains(), BuiltinCount(),
-    BuiltinCurrentLibraryName(), BuiltinCurrentLibraryPath(),
-    BuiltinDaysBetween(), BuiltinDivide(), BuiltinEval(), BuiltinFirstNonEmpty(),
-    BuiltinField(), BuiltinFinishFormatting(), BuiltinFormatDate(),
-    BuiltinFormatNumber(), BuiltinFormatsModtimes(), BuiltinFormatsPaths(),
-    BuiltinFormatsSizes(),
-    BuiltinHasCover(), BuiltinHumanReadable(), BuiltinIdentifierInList(),
-    BuiltinIfempty(), BuiltinLanguageCodes(), BuiltinLanguageStrings(),
-    BuiltinInList(), BuiltinListDifference(), BuiltinListEquals(),
-    BuiltinListIntersection(), BuiltinListitem(), BuiltinListRe(),
-    BuiltinListSort(), BuiltinListUnion(), BuiltinLookup(),
-    BuiltinLowercase(), BuiltinMultiply(), BuiltinNot(),
-    BuiltinOndevice(), BuiltinOr(), BuiltinPrint(), BuiltinRawField(),
-    BuiltinRe(), BuiltinSelect(), BuiltinSeriesSort(), BuiltinShorten(),
-    BuiltinStrcat(), BuiltinStrcatMax(),
-    BuiltinStrcmp(), BuiltinStrInList(), BuiltinStrlen(), BuiltinSubitems(),
-    BuiltinSublist(),BuiltinSubstr(), BuiltinSubtract(), BuiltinSwapAroundComma(),
-    BuiltinSwitch(), BuiltinTemplate(), BuiltinTest(), BuiltinTitlecase(),
-    BuiltinToday(), BuiltinUppercase(),
+    BuiltinAdd, BuiltinAnd, BuiltinApproximateFormats,
+    BuiltinAssign, BuiltinBooksize,
+    BuiltinCapitalize, BuiltinCmp, BuiltinContains, BuiltinCount,
+    BuiltinCurrentLibraryName, BuiltinCurrentLibraryPath,
+    BuiltinDaysBetween, BuiltinDivide, BuiltinEval, BuiltinFirstNonEmpty,
+    BuiltinField, BuiltinFinishFormatting, BuiltinFormatDate,
+    BuiltinFormatNumber, BuiltinFormatsModtimes, BuiltinFormatsPaths,
+    BuiltinFormatsSizes,
+    BuiltinHasCover, BuiltinHumanReadable, BuiltinIdentifierInList,
+    BuiltinIfempty, BuiltinLanguageCodes, BuiltinLanguageStrings,
+    BuiltinInList, BuiltinListDifference, BuiltinListEquals,
+    BuiltinListIntersection, BuiltinListitem, BuiltinListRe,
+    BuiltinListSort, BuiltinListUnion, BuiltinLookup,
+    BuiltinLowercase, BuiltinMultiply, BuiltinNot,
+    BuiltinOndevice, BuiltinOr, BuiltinPrint, BuiltinRawField,
+    BuiltinRe, BuiltinSelect, BuiltinSeriesSort, BuiltinShorten,
+    BuiltinStrcat, BuiltinStrcatMax,
+    BuiltinStrcmp, BuiltinStrInList, BuiltinStrlen, BuiltinSubitems,
+    BuiltinSublist,BuiltinSubstr, BuiltinSubtract, BuiltinSwapAroundComma,
+    BuiltinSwitch, BuiltinTemplate, BuiltinTest, BuiltinTitlecase,
+    BuiltinToday, BuiltinUppercase,
 ]
 
 class FormatterUserFunction(FormatterFunction):
@@ -1260,10 +1275,11 @@ class UserFunction(FormatterUserFunction):
     return cls
 
 def load_user_template_functions(funcs):
-    formatter_functions().reset_to_builtins()
-    for func in funcs:
-        try:
-            cls = compile_user_function(*func)
-            formatter_functions().register_function(cls)
-        except:
-            traceback.print_exc()
+    if funcs:
+        formatter_functions().reset_to_builtins()
+        for func in funcs:
+            try:
+                cls = compile_user_function(*func)
+                formatter_functions().register_function(cls)
+            except:
+                traceback.print_exc()