Recursively print chained exceptions

Author: jepler

locale/circuitpython.pot

@@ -178,7 +178,7 @@ msgstr ""
 msgid "%q must be of type %q"
 msgstr ""
 
-#: shared-bindings/digitalio/Pull.c
+#: py/objexcept.c shared-bindings/digitalio/Pull.c
 msgid "%q must be of type %q or None"
 msgstr ""
 
@@ -882,6 +882,10 @@ msgstr ""
 msgid "Drive mode not used when direction is input."
 msgstr ""
 
+#: py/obj.c
+msgid "During handling of the above exception, another exception occurred:"
+msgstr ""
+
 #: shared-bindings/aesio/aes.c
 msgid "ECB only operates on 16 bytes at a time"
 msgstr ""
@@ -1979,6 +1983,10 @@ msgid ""
 "exit safe mode."
 msgstr ""
 
+#: py/obj.c
+msgid "The above exception was the direct cause of the following exception:"
+msgstr ""
+
 #: shared-bindings/rgbmatrix/RGBMatrix.c
 msgid "The length of rgb_pins must be 6, 12, 18, 24, or 30"
 msgstr ""
@@ -3308,10 +3316,6 @@ msgstr ""
 msgid "invalid syntax for number"
 msgstr ""
 
-#: py/objexcept.c
-msgid "invalid traceback"
-msgstr ""
-
 #: py/objtype.c
 msgid "issubclass() arg 1 must be a class"
 msgstr ""

py/obj.c

@@ -142,9 +142,33 @@ void mp_obj_print(mp_obj_t o_in, mp_print_kind_t kind) {
     mp_obj_print_helper(MP_PYTHON_PRINTER, o_in, kind);
 }
 
+static void mp_obj_print_inner_exception(const mp_print_t *print, mp_obj_t self_in, mp_int_t limit) {
+    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+    mp_obj_exception_t *self = mp_obj_exception_get_native(self_in);
+    const compressed_string_t *msg = MP_ERROR_TEXT("During handling of the above exception, another exception occurred:");
+    mp_obj_exception_t *inner = NULL;
+    if (self->cause) {
+        msg = MP_ERROR_TEXT("The above exception was the direct cause of the following exception:");
+        inner = self->cause;
+    } else if (!self->suppress_context) {
+        inner = self->context;
+    }
+    if (inner && !inner->marked) {
+        inner->marked = true;
+        mp_obj_print_exception_with_limit(print, MP_OBJ_FROM_PTR(inner), limit);
+        inner->marked = false;
+        mp_printf(print, "\n");
+        mp_cprintf(print, msg);
+        mp_printf(print, "\n\n");
+    }
+    #endif
+}
+
 // helper function to print an exception with traceback
 void mp_obj_print_exception_with_limit(const mp_print_t *print, mp_obj_t exc, mp_int_t limit) {
     if (mp_obj_is_exception_instance(exc) && stack_ok()) {
+        mp_obj_print_inner_exception(print, exc, limit);
+
         size_t n, *values;
         mp_obj_exception_get_traceback(exc, &n, &values);
         if (n > 0) {

py/objexcept.h

@@ -34,8 +34,11 @@ typedef struct _mp_obj_exception_t {
     mp_obj_base_t base;
     mp_obj_tuple_t *args;
     mp_obj_traceback_t *traceback;
-    mp_obj_t cause, context;
+    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+    struct _mp_obj_exception_t *cause, *context;
     bool suppress_context;
+    bool marked;
+    #endif
 } mp_obj_exception_t;
 
 void mp_obj_exception_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t kind);

tests/circuitpython/traceback_test_chained.py

@@ -0,0 +1,55 @@
+try:
+    Exception().__cause__
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+try:
+    import traceback
+except:
+    print("SKIP")
+    raise SystemExit
+
+
+def print_exc_info(e):
+    print("-" * 72)
+    traceback.print_exception(None, e, e.__traceback__)
+    print("-" * 72)
+    print()
+
+
+try:
+    try:
+        1 / 0
+    except Exception as inner:
+        raise RuntimeError() from inner
+except Exception as e:
+    print_exc_info(e)
+print()
+
+try:
+    try:
+        1 / 0
+    except Exception as inner:
+        raise RuntimeError() from OSError()
+except Exception as e:
+    print_exc_info(e)
+print()
+
+
+try:
+    try:
+        1 / 0
+    except Exception as inner:
+        raise RuntimeError()
+except Exception as e:
+    print_exc_info(e)
+print()
+
+try:
+    try:
+        1 / 0
+    except Exception as inner:
+        raise RuntimeError() from None
+except Exception as e:
+    print_exc_info(e)

tests/circuitpython/traceback_test_chained.py.exp

@@ -0,0 +1,43 @@
+------------------------------------------------------------------------
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 23, in <module>
+ZeroDivisionError: division by zero
+
+The above exception was the direct cause of the following exception:
+
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 25, in <module>
+RuntimeError: 
+------------------------------------------------------------------------
+
+
+------------------------------------------------------------------------
+OSError: 
+
+The above exception was the direct cause of the following exception:
+
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 34, in <module>
+RuntimeError: 
+------------------------------------------------------------------------
+
+
+------------------------------------------------------------------------
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 42, in <module>
+ZeroDivisionError: division by zero
+
+During handling of the above exception, another exception occurred:
+
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 44, in <module>
+RuntimeError: 
+------------------------------------------------------------------------
+
+
+------------------------------------------------------------------------
+Traceback (most recent call last):
+  File "circuitpython/traceback_test_chained.py", line 53, in <module>
+RuntimeError: 
+------------------------------------------------------------------------
+