add event name to watcher callback error message

Author: carljm

Include/cpython/code.h

@@ -224,9 +224,14 @@ PyAPI_FUNC(int) PyCode_Addr2Line(PyCodeObject *, int);
 
 PyAPI_FUNC(int) PyCode_Addr2Location(PyCodeObject *, int, int *, int *, int *, int *);
 
-typedef enum PyCodeEvent {
-  PY_CODE_EVENT_CREATE,
-  PY_CODE_EVENT_DESTROY
+#define FOREACH_CODE_EVENT(V) \
+    V(CREATE)                 \
+    V(DESTROY)
+
+typedef enum {
+    #define DEF_EVENT(op) PY_CODE_EVENT_##op,
+    FOREACH_CODE_EVENT(DEF_EVENT)
+    #undef DEF_EVENT
 } PyCodeEvent;
 
 
@@ -236,7 +241,7 @@ typedef enum PyCodeEvent {
  * The callback is invoked with a borrowed reference to co, after it is
  * created and before it is destroyed.
  *
- * If the callback returns with an exception set, it must return -1. Otherwise
+ * If the callback sets an exception, it must return -1. Otherwise
  * it should return 0.
  */
 typedef int (*PyCode_WatchCallback)(

Include/cpython/dictobject.h

@@ -16,11 +16,11 @@ typedef struct {
 
     /* Dictionary version: globally unique, value change each time
        the dictionary is modified */
-#ifdef Py_BUILD_CORE       
+#ifdef Py_BUILD_CORE
     uint64_t ma_version_tag;
 #else
     Py_DEPRECATED(3.12) uint64_t ma_version_tag;
-#endif        
+#endif
 
     PyDictKeysObject *ma_keys;
 
@@ -90,13 +90,18 @@ PyAPI_FUNC(PyObject *) _PyDictView_Intersect(PyObject* self, PyObject *other);
 
 /* Dictionary watchers */
 
+#define FOREACH_DICT_EVENT(V) \
+    V(ADDED)                  \
+    V(MODIFIED)               \
+    V(DELETED)                \
+    V(CLONED)                 \
+    V(CLEARED)                \
+    V(DEALLOCATED)
+
 typedef enum {
-    PyDict_EVENT_ADDED,
-    PyDict_EVENT_MODIFIED,
-    PyDict_EVENT_DELETED,
-    PyDict_EVENT_CLONED,
-    PyDict_EVENT_CLEARED,
-    PyDict_EVENT_DEALLOCATED,
+    #define DEF_EVENT(EVENT) PyDict_EVENT_##EVENT,
+    FOREACH_DICT_EVENT(DEF_EVENT)
+    #undef DEF_EVENT
 } PyDict_WatchEvent;
 
 // Callback to be invoked when a watched dict is cleared, dealloced, or modified.

Lib/test/test_capi/test_watchers.py

@@ -110,7 +110,7 @@ def test_error(self):
             with catch_unraisable_exception() as cm:
                 d["foo"] = "bar"
                 self.assertIn(
-                    "watcher callback for <dict at",
+                    "PyDict_EVENT_ADDED watcher callback for <dict at",
                     cm.unraisable.object
                 )
                 self.assertEqual(str(cm.unraisable.exc_value), "boom!")
@@ -405,7 +405,10 @@ def test_error(self):
             with catch_unraisable_exception() as cm:
                 co = _testcapi.code_newempty("test_watchers", "dummy0", 0)
 
-                self.assertEqual(cm.unraisable.object, f"watcher callback for {co!r}")
+                self.assertEqual(
+                    cm.unraisable.object,
+                    f"PY_CODE_EVENT_CREATE watcher callback for {co!r}"
+                )
                 self.assertEqual(str(cm.unraisable.exc_value), "boom!")
 
     def test_dealloc_error(self):
@@ -508,7 +511,7 @@ def myfunc():
 
                 self.assertEqual(
                     cm.unraisable.object,
-                    f"watcher callback for {myfunc!r}"
+                    f"PyFunction_EVENT_CREATE watcher callback for {myfunc!r}"
                 )
 
     def test_dealloc_watcher_raises_error(self):

Objects/codeobject.c

@@ -13,6 +13,17 @@
 
 static PyObject* code_repr(PyCodeObject *co);
 
+static const char *
+code_event_name(PyCodeEvent event) {
+    switch (event) {
+        #define CASE(op)                \
+        case PY_CODE_EVENT_##op:         \
+            return "PY_CODE_EVENT_" #op;
+        FOREACH_CODE_EVENT(CASE)
+        #undef CASE
+    }
+}
+
 static void
 notify_code_watchers(PyCodeEvent event, PyCodeObject *co)
 {
@@ -33,7 +44,9 @@ notify_code_watchers(PyCodeEvent event, PyCodeObject *co)
                 PyObject *context = NULL;
                 PyObject *repr = code_repr(co);
                 if (repr) {
-                    context = PyUnicode_FromFormat("watcher callback for %U", repr);
+                    context = PyUnicode_FromFormat(
+                        "%s watcher callback for %U",
+                        code_event_name(event), repr);
                     Py_DECREF(repr);
                 }
                 if (context == NULL) {

Objects/dictobject.c

@@ -5739,6 +5739,17 @@ PyDict_ClearWatcher(int watcher_id)
     return 0;
 }
 
+static const char *
+dict_event_name(PyDict_WatchEvent event) {
+    switch (event) {
+        #define CASE(op)                \
+        case PyDict_EVENT_##op:         \
+            return "PyDict_EVENT_" #op;
+        FOREACH_DICT_EVENT(CASE)
+        #undef CASE
+    }
+}
+
 void
 _PyDict_SendEvent(int watcher_bits,
                   PyDict_WatchEvent event,
@@ -5756,7 +5767,8 @@ _PyDict_SendEvent(int watcher_bits,
                 // dict as context, just an informative string message.  Dict
                 // repr can call arbitrary code, so we invent a simpler version.
                 PyObject *context = PyUnicode_FromFormat(
-                    "watcher callback for <dict at %p>", mp);
+                    "%s watcher callback for <dict at %p>",
+                    dict_event_name(event), mp);
                 if (context == NULL) {
                     context = Py_NewRef(Py_None);
                 }

Objects/funcobject.c

@@ -10,6 +10,17 @@
 
 static PyObject* func_repr(PyFunctionObject *op);
 
+static const char *
+func_event_name(PyFunction_WatchEvent event) {
+    switch (event) {
+        #define CASE(op)                \
+        case PyFunction_EVENT_##op:         \
+            return "PyFunction_EVENT_" #op;
+        FOREACH_FUNC_EVENT(CASE)
+        #undef CASE
+    }
+}
+
 static void
 notify_func_watchers(PyInterpreterState *interp, PyFunction_WatchEvent event,
                      PyFunctionObject *func, PyObject *new_value)
@@ -28,7 +39,9 @@ notify_func_watchers(PyInterpreterState *interp, PyFunction_WatchEvent event,
                 PyObject *context = NULL;
                 PyObject *repr = func_repr(func);
                 if (repr != NULL) {
-                    context = PyUnicode_FromFormat("watcher callback for %U", repr);
+                    context = PyUnicode_FromFormat(
+                        "%s watcher callback for %U",
+                        func_event_name(event), repr);
                     Py_DECREF(repr);
                 }
                 if (context == NULL) {