simplify code generated for f-string formatting using simple utility functions

Cython/Compiler/ExprNodes.py

@@ -3029,40 +3029,28 @@ class FormattedValueNode(ExprNode):
         return self
 
     def generate_result_code(self, code):
-        conversion_result = value_result = self.value.py_result()
+        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.conversion_char:
             fn = self.find_conversion_func(self.conversion_char)
-            if fn is None:
-                assert False, "invalid conversion character found: '%s'" % self.conversion_char
-
-            code.putln('{')
-            conversion_result = Naming.quick_temp_cname
-            code.putln('PyObject *%s = %s(%s); %s' % (
-                conversion_result,
-                fn,
-                value_result,
-                code.error_goto_if_null(conversion_result, self.pos)
-            ))
-            code.put_gotref(conversion_result)
-
-        if isinstance(self.format_spec, UnicodeNode) and not self.format_spec.value:
-            # common case: no format spec => expect Unicode pass-through
+            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:
+            code.globalstate.use_utility_code(UtilityCode.load_cached("PyObjectFormatSimple", "StringTools.c"))
             format_func = '__Pyx_PyObject_FormatSimple'
         else:
             format_func = 'PyObject_Format'
 
-        code.put("%s = %s(%s, %s); " % (
+        code.putln("%s = %s(%s, %s); %s" % (
             self.result(),
             format_func,
-            conversion_result,
-            self.format_spec.py_result()))
-
-        if self.conversion_char:
-            code.put_decref(conversion_result, py_object_type)
-            code.putln('}')
-
-        code.putln(code.error_goto_if_null(self.result(), self.pos))
+            value_result,
+            self.format_spec.py_result(),
+            code.error_goto_if_null(self.result(), self.pos)))
         code.put_gotref(self.py_result())
 
 

Cython/Utility/ModuleSetupCode.c

@@ -123,7 +123,6 @@
   #define PyObject_Realloc(p)  PyMem_Realloc(p)
 #endif
 
-#define __Pyx_PyObject_FormatSimple(s, f) (likely(PyUnicode_CheckExact(s)) ? (Py_INCREF(s), s) : PyObject_Format(s, f))
 #define __Pyx_PyString_FormatSafe(a, b)   ((unlikely((a) == Py_None)) ? PyNumber_Remainder(a, b) : __Pyx_PyString_Format(a, b))
 #define __Pyx_PyUnicode_FormatSafe(a, b)  ((unlikely((a) == Py_None)) ? PyNumber_Remainder(a, b) : PyUnicode_Format(a, b))
 

Cython/Utility/StringTools.c

@@ -811,3 +811,23 @@ static CYTHON_INLINE int __Pyx_PyByteArray_Append(PyObject* bytearray, int value
     Py_DECREF(retval);
     return 0;
 }
+
+
+//////////////////// PyObjectFormatSimple.proto ////////////////////
+
+#define __Pyx_PyObject_FormatSimple(s, f) (likely(PyUnicode_CheckExact(s)) ? (Py_INCREF(s), s) : PyObject_Format(s, f))
+
+
+//////////////////// PyObjectFormatAndDecref.proto ////////////////////
+
+#define __Pyx_PyObject_FormatSimpleAndDecref(s, f) \
+    ((unlikely(!s) || likely(PyUnicode_CheckExact(s))) ? s : __Pyx_PyObject_FormatAndDecref(s, f))
+static CYTHON_INLINE PyObject* __Pyx_PyObject_FormatAndDecref(PyObject* s, PyObject* f);
+
+//////////////////// PyObjectFormatAndDecref ////////////////////
+
+static CYTHON_INLINE PyObject* __Pyx_PyObject_FormatAndDecref(PyObject* s, PyObject* f) {
+    PyObject *result = PyObject_Format(s, f);
+    Py_DECREF(s);
+    return result;
+}