1 files changed, 68 insertions, 4 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 5fa555e..dd9360c 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2307,7 +2307,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             }
             else {
                 v = PyObject_GetItem(locals, name);
-                if (v == NULL && _PyErr_OCCURRED()) {
+                if (v == NULL) {
                     if (!PyErr_ExceptionMatches(PyExc_KeyError))
                         goto error;
                     PyErr_Clear();
@@ -2347,26 +2347,33 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             PyObject *name = GETITEM(names, oparg);
             PyObject *v;
             if (PyDict_CheckExact(f->f_globals)
-                && PyDict_CheckExact(f->f_builtins)) {
+                && PyDict_CheckExact(f->f_builtins))
+            {
                 v = _PyDict_LoadGlobal((PyDictObject *)f->f_globals,
                                        (PyDictObject *)f->f_builtins,
                                        name);
                 if (v == NULL) {
-                    if (!_PyErr_OCCURRED())
+                    if (!_PyErr_OCCURRED()) {
+                        /* _PyDict_LoadGlobal() returns NULL without raising
+                         * an exception if the key doesn't exist */
                         format_exc_check_arg(PyExc_NameError,
                                              NAME_ERROR_MSG, name);
+                    }
                     goto error;
                 }
                 Py_INCREF(v);
             }
             else {
                 /* Slow-path if globals or builtins is not a dict */
+
+                /* namespace 1: globals */
                 v = PyObject_GetItem(f->f_globals, name);
                 if (v == NULL) {
                     if (!PyErr_ExceptionMatches(PyExc_KeyError))
                         goto error;
                     PyErr_Clear();
 
+                    /* namespace 2: builtins */
                     v = PyObject_GetItem(f->f_builtins, name);
                     if (v == NULL) {
                         if (PyErr_ExceptionMatches(PyExc_KeyError))
@@ -2426,7 +2433,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             }
             else {
                 value = PyObject_GetItem(locals, name);
-                if (value == NULL && PyErr_Occurred()) {
+                if (value == NULL) {
                     if (!PyErr_ExceptionMatches(PyExc_KeyError))
                         goto error;
                     PyErr_Clear();
@@ -3366,6 +3373,63 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             DISPATCH();
         }
 
+        TARGET(FORMAT_VALUE) {
+            /* Handles f-string value formatting. */
+            PyObject *result;
+            PyObject *fmt_spec;
+            PyObject *value;
+            PyObject *(*conv_fn)(PyObject *);
+            int which_conversion = oparg & FVC_MASK;
+            int have_fmt_spec = (oparg & FVS_MASK) == FVS_HAVE_SPEC;
+
+            fmt_spec = have_fmt_spec ? POP() : NULL;
+            value = TOP();
+
+            /* See if any conversion is specified. */
+            switch (which_conversion) {
+            case FVC_STR:   conv_fn = PyObject_Str;   break;
+            case FVC_REPR:  conv_fn = PyObject_Repr;  break;
+            case FVC_ASCII: conv_fn = PyObject_ASCII; break;
+
+            /* Must be 0 (meaning no conversion), since only four
+               values are allowed by (oparg & FVC_MASK). */
+            default:        conv_fn = NULL;           break;
+            }
+
+            /* If there's a conversion function, call it and replace
+               value with that result. Otherwise, just use value,
+               without conversion. */
+            if (conv_fn) {
+                result = conv_fn(value);
+                Py_DECREF(value);
+                if (!result) {
+                    Py_XDECREF(fmt_spec);
+                    goto error;
+                }
+                value = result;
+            }
+
+            /* If value is a unicode object, and there's no fmt_spec,
+               then we know the result of format(value) is value
+               itself. In that case, skip calling format(). I plan to
+               move this optimization in to PyObject_Format()
+               itself. */
+            if (PyUnicode_CheckExact(value) && fmt_spec == NULL) {
+                /* Do nothing, just transfer ownership to result. */
+                result = value;
+            } else {
+                /* Actually call format(). */
+                result = PyObject_Format(value, fmt_spec);
+                Py_DECREF(value);
+                Py_XDECREF(fmt_spec);
+                if (!result)
+                    goto error;
+            }
+
+            SET_TOP(result);
+            DISPATCH();
+        }
+
         TARGET(EXTENDED_ARG) {
             opcode = NEXTOP();
             oparg = oparg<<16 | NEXTARG();