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Add PyExc_ImportCycleError and raise it when a cycle is detected

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This commit is contained in:
Dino Viehland 2025-09-29 10:19:34 -07:00
parent 00e7800e4c
commit 781eedb9d4
9 changed files with 57 additions and 15 deletions
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45
Python/import.c
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@ -3710,6 +3710,33 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
PyLazyImportObject *lz = (PyLazyImportObject *)lazy_import;
// Check if we are already importing this module, if so, then we want to return an error
// that indicates we've hit a cycle which will indicate the value isn't yet available.
PyInterpreterState *interp = tstate->interp;
PyObject *importing = interp->imports.lazy_importing_modules;
if (importing == NULL) {
importing = interp->imports.lazy_importing_modules = PySet_New(NULL);
if (importing == NULL) {
return NULL;
}
}
int is_loading = PySet_Contains(importing, lazy_import);
if (is_loading < 0 ) {
return NULL;
} else if (is_loading == 1) {
PyObject *name = _PyLazyImport_GetName(lazy_import);
PyObject *errmsg = PyUnicode_FromFormat("cannot import name %R "
"(most likely due to a circular import)",
name);
PyErr_SetImportErrorSubclass(PyExc_ImportCycleError, errmsg, lz->lz_from, NULL);
Py_XDECREF(errmsg);
Py_XDECREF(name);
return NULL;
} else if (PySet_Add(importing, lazy_import) < 0) {
goto error;
}
Py_ssize_t dot = -1;
int full = 0;
if (lz->lz_attr != NULL) {
@ -3738,10 +3765,6 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
PyObject *globals = PyEval_GetGlobals();
// Increment counter to prevent recursive lazy import creation
PyInterpreterState *interp = tstate->interp;
interp->imports.lazy_import_resolution_depth++;
if (full) {
obj = _PyEval_ImportNameWithImport(tstate,
lz->lz_import_func,
@ -3753,7 +3776,6 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
} else {
PyObject *name = PyUnicode_Substring(lz->lz_from, 0, dot);
if (name == NULL) {
interp->imports.lazy_import_resolution_depth--;
goto error;
}
obj = _PyEval_ImportNameWithImport(tstate,
@ -3766,9 +3788,6 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
Py_DECREF(name);
}
// Decrement counter
interp->imports.lazy_import_resolution_depth--;
if (obj == NULL) {
goto error;
}
@ -3860,6 +3879,11 @@ _PyImport_LoadLazyImportTstate(PyThreadState *tstate, PyObject *lazy_import)
}
ok:
if (PySet_Discard(importing, lazy_import) < 0) {
Py_DECREF(obj);
obj = NULL;
}
Py_XDECREF(fromlist);
return obj;
}
@ -3950,8 +3974,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
goto error;
}
// Only check __lazy_modules__ if we're not already resolving a lazy import
if (interp->imports.lazy_import_resolution_depth == 0 && globals != NULL &&
if (globals != NULL &&
PyMapping_GetOptionalItem(globals, &_Py_ID(__lazy_modules__), &lazy_modules) < 0) {
goto error;
}
@ -3974,7 +3997,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *globals,
goto error;
}
if (interp->imports.lazy_import_resolution_depth == 0 && lazy_modules != NULL) {
if (lazy_modules != NULL) {
// Check and see if the module is opting in w/o syntax for backwards compatibility
// with older Python versions.
int contains = PySequence_Contains(lazy_modules, name);