set FormattedValueNode.format_spec field to None for empty format specs to...

set FormattedValueNode.format_spec field to None for empty format specs to simplify later "empty" tests

Cython/Compiler/ExprNodes.py

@@ -3025,23 +3025,28 @@ class FormattedValueNode(ExprNode):
 
     def analyse_types(self, env):
         self.value = self.value.analyse_types(env).coerce_to_pyobject(env)
-        self.format_spec = self.format_spec.analyse_types(env).coerce_to_pyobject(env)
+        if self.format_spec:
+            self.format_spec = self.format_spec.analyse_types(env).coerce_to_pyobject(env)
         return self
 
     def generate_result_code(self, code):
         value_result = self.value.py_result()
-        # common case: expect Unicode pass-through if no format spec
-        no_format_spec = isinstance(self.format_spec, UnicodeNode) and not self.format_spec.value.strip()
+        if self.format_spec:
+            format_func = '__Pyx_PyObject_Format'
+            format_spec = self.format_spec.py_result()
+        else:
+            # common case: expect simple Unicode pass-through if no format spec
+            format_func = '__Pyx_PyObject_FormatSimple'
+            format_spec = Naming.empty_unicode
 
         if self.conversion_char:
             fn = self.find_conversion_func(self.conversion_char)
             assert fn is not None, "invalid conversion character found: '%s'" % self.conversion_char
             value_result = '%s(%s)' % (fn, value_result)
             code.globalstate.use_utility_code(UtilityCode.load_cached("PyObjectFormatAndDecref", "StringTools.c"))
-            format_func = '__Pyx_PyObject_FormatSimpleAndDecref' if no_format_spec else '__Pyx_PyObject_FormatAndDecref'
-        elif no_format_spec:
+            format_func += 'AndDecref'
+        elif not self.format_spec:
             code.globalstate.use_utility_code(UtilityCode.load_cached("PyObjectFormatSimple", "StringTools.c"))
-            format_func = '__Pyx_PyObject_FormatSimple'
         else:
             format_func = 'PyObject_Format'
 
@@ -3049,7 +3054,7 @@ class FormattedValueNode(ExprNode):
             self.result(),
             format_func,
             value_result,
-            self.format_spec.py_result(),
+            format_spec,
             code.error_goto_if_null(self.result(), self.pos)))
         code.put_gotref(self.py_result())
 

Cython/Compiler/Optimize.py

@@ -3960,18 +3960,24 @@ class ConstantFolding(Visitor.VisitorTransform, SkipDeclarations):
         """
         self.visitchildren(node)
         unicode_node = ExprNodes.UnicodeNode
+        format_node = ExprNodes.FormattedValueNode
+
         values = []
         for is_unode_group, substrings in itertools.groupby(node.values, lambda v: isinstance(v, unicode_node)):
             if is_unode_group:
                 substrings = list(substrings)
                 unode = substrings[0]
                 if len(substrings) > 1:
-                    unode.value = EncodedString(u''.join(node.value for node in substrings))
+                    unode.value = EncodedString(u''.join(value.value for value in substrings))
                 # ignore empty Unicode strings
                 if unode.value:
                     values.append(unode)
             else:
-                values.extend(substrings)
+                for value in substrings:
+                    if isinstance(value, format_node):
+                        if isinstance(value.format_spec, unicode_node) and not value.format_spec.value:
+                            value.format_spec = None
+                    values.append(value)
 
         if not values:
             node = ExprNodes.UnicodeNode(node.pos, value=EncodedString(''))

Cython/Compiler/Parsing.py

@@ -1031,7 +1031,7 @@ def p_f_string_expr(s, unicode_value, pos, starting_index):
     i = starting_index
     size = len(unicode_value)
     conversion_char = terminal_char = format_spec = None
-    format_spec_str = u''
+    format_spec_str = None
     NO_CHAR = 2**30
 
     nested_depth = 0
@@ -1133,7 +1133,7 @@ def p_f_string_expr(s, unicode_value, pos, starting_index):
         s.error("invalid conversion character '%s'" % conversion_char)
 
     # the format spec is itself treated like an f-string
-    if format_spec_str is not None:
+    if format_spec_str:
         format_spec = ExprNodes.JoinedStrNode(pos, values=p_f_string(s, format_spec_str, pos))
 
     return i + 1, ExprNodes.FormattedValueNode(