PEP 750 bug and spec fix (python#58)

davepeck · lysnikolaou · web-flow · commit 6a7b4488f962 · 2025-04-09T18:29:29.000+02:00
* Bugfix: increment `interpolationsidx` in `template_new()`
* Spec fix: don't return empty strings from `templateiter_next()`
---------

Co-authored-by: Lysandros Nikolaou &lt;lisandrosnik@gmail.com&gt;
diff --git a/Objects/templateobject.c b/Objects/templateobject.c
@@ -22,10 +22,15 @@ templateiter_next(templateiterobject *self)
     PyObject *item;
     if (self->from_strings) {
         item = PyIter_Next(self->stringsiter);
+        self->from_strings = 0;
+        if (PyUnicode_GET_LENGTH(item) == 0) {
+            Py_SETREF(item, PyIter_Next(self->interpolationsiter));
+            self->from_strings = 1;
+        }
     } else {
         item = PyIter_Next(self->interpolationsiter);
+        self->from_strings = 1;
     }
-    self->from_strings = !self->from_strings;
     return item;
 }
 
@@ -133,7 +138,7 @@ template_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
             if (!last_was_str) {
                 PyTuple_SET_ITEM(strings, stringsidx++, &_Py_STR(empty));
             }
-            PyTuple_SET_ITEM(interpolations, interpolationsidx, Py_NewRef(item));
+            PyTuple_SET_ITEM(interpolations, interpolationsidx++, Py_NewRef(item));
             last_was_str = 0;
         }
     }

Original file line number	Diff line number	Diff line change
`@@ -22,10 +22,15 @@ templateiter_next(templateiterobject *self)`
`22`	`22`	`PyObject *item;`
`23`	`23`	`if (self->from_strings) {`
`24`	`24`	`item = PyIter_Next(self->stringsiter);`
	`25`	`+ self->from_strings = 0;`
	`26`	`+ if (PyUnicode_GET_LENGTH(item) == 0) {`
	`27`	`+ Py_SETREF(item, PyIter_Next(self->interpolationsiter));`
	`28`	`+ self->from_strings = 1;`
	`29`	`+ }`
`25`	`30`	`} else {`
`26`	`31`	`item = PyIter_Next(self->interpolationsiter);`
	`32`	`+ self->from_strings = 1;`
`27`	`33`	`}`
`28`		`- self->from_strings = !self->from_strings;`
`29`	`34`	`return item;`
`30`	`35`	`}`
`31`	`36`
`@@ -133,7 +138,7 @@ template_new(PyTypeObject type, PyObject args, PyObject *kwds)`
`133`	`138`	`if (!last_was_str) {`
`134`	`139`	`PyTuple_SET_ITEM(strings, stringsidx++, &_Py_STR(empty));`
`135`	`140`	`}`
`136`		`- PyTuple_SET_ITEM(interpolations, interpolationsidx, Py_NewRef(item));`
	`141`	`+ PyTuple_SET_ITEM(interpolations, interpolationsidx++, Py_NewRef(item));`
`137`	`142`	`last_was_str = 0;`
`138`	`143`	`}`
`139`	`144`	`}`