Implement chained exceptions

locale/circuitpython.pot

@@ -106,7 +106,7 @@ msgstr ""
 msgid "%q in use"
 msgstr ""
 
-#: py/obj.c py/objstr.c py/objstrunicode.c
+#: py/objstr.c py/objstrunicode.c
 msgid "%q index out of range"
 msgstr ""
 
@@ -171,11 +171,11 @@ msgstr ""
 msgid "%q must be an int"
 msgstr ""
 
-#: py/argcheck.c
+#: py/argcheck.c py/obj.c
 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 ""
 
@@ -894,6 +894,10 @@ 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 ""
@@ -2007,6 +2011,10 @@ msgid ""
 "exit safe mode."
 msgstr ""
 
+#: py/obj.c
+msgid "The above exception was the direct cause of the following exception:"
+msgstr ""
+
 #: ports/espressif/boards/m5stack_atom_lite/mpconfigboard.h
 msgid "The central button was pressed at start up.\n"
 msgstr ""
@@ -3153,7 +3161,7 @@ msgid "index is out of bounds"
 msgstr ""
 
 #: extmod/ulab/code/numpy/numerical.c extmod/ulab/code/ulab_tools.c
-#: ports/espressif/common-hal/pulseio/PulseIn.c py/obj.c
+#: ports/espressif/common-hal/pulseio/PulseIn.c
 #: shared-bindings/bitmaptools/__init__.c
 msgid "index out of range"
 msgstr ""
@@ -3336,10 +3344,6 @@ 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 ""

ports/unix/variants/coverage/mpconfigvariant.h

@@ -65,6 +65,7 @@
 #define MICROPY_PY_UCRYPTOLIB          (1)
 #define MICROPY_PY_UCRYPTOLIB_CTR      (1)
 #define MICROPY_PY_MICROPYTHON_HEAP_LOCKED (1)
+#define MICROPY_CPYTHON_EXCEPTION_CHAIN (1)
 
 // use vfs's functions for import stat and builtin open
 #define mp_import_stat mp_vfs_import_stat

py/circuitpy_mpconfig.h

@@ -224,6 +224,9 @@ typedef long mp_off_t;
 #ifndef MICROPY_CPYTHON_COMPAT
 #define MICROPY_CPYTHON_COMPAT                (CIRCUITPY_FULL_BUILD)
 #endif
+#ifndef MICROPY_CPYTHON_EXCEPTION_CHAIN
+#define MICROPY_CPYTHON_EXCEPTION_CHAIN       (CIRCUITPY_FULL_BUILD)
+#endif
 #define MICROPY_PY_BUILTINS_POW3              (CIRCUITPY_BUILTINS_POW3)
 #define MICROPY_PY_FSTRINGS                   (1)
 #define MICROPY_MODULE_WEAK_LINKS             (0)

py/mpconfig.h

@@ -773,6 +773,16 @@ typedef long long mp_longint_impl_t;
 #define MICROPY_WARNINGS (0)
 #endif
 
+// Whether to support chained exceptions
+#ifndef MICROPY_CPYTHON_EXCEPTION_CHAIN
+#define MICROPY_CPYTHON_EXCEPTION_CHAIN (0)
+#endif
+
+// Whether the statically allocated GeneratorExit exception may be const
+#ifndef MICROPY_CONST_GENERATOREXIT_OBJ
+#define MICROPY_CONST_GENERATOREXIT_OBJ (!MICROPY_CPYTHON_EXCEPTION_CHAIN)
+#endif
+
 // Whether to support warning categories
 #ifndef MICROPY_WARNINGS_CATEGORY
 #define MICROPY_WARNINGS_CATEGORY (0)

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/obj.h

@@ -791,7 +791,9 @@ extern const struct _mp_obj_dict_t mp_const_empty_dict_obj;
 extern const struct _mp_obj_traceback_t mp_const_empty_traceback_obj;
 extern const struct _mp_obj_singleton_t mp_const_ellipsis_obj;
 extern const struct _mp_obj_singleton_t mp_const_notimplemented_obj;
-extern const struct _mp_obj_exception_t mp_const_GeneratorExit_obj;
+#if MICROPY_CONST_GENERATOREXIT_OBJ
+extern const struct _mp_obj_exception_t mp_static_GeneratorExit_obj;
+#endif
 
 // Fixed empty map. Useful when calling keyword-receiving functions
 // without any keywords from C, etc.

py/objexcept.c

@@ -218,19 +218,45 @@ void mp_obj_exception_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
     mp_obj_exception_t *self = MP_OBJ_TO_PTR(self_in);
     if (dest[0] != MP_OBJ_NULL) {
         // store/delete attribute
-        if (self == &mp_const_GeneratorExit_obj) {
+        #if MICROPY_CONST_GENERATOREXIT_OBJ
+        if (self == &mp_static_GeneratorExit_obj) {
             mp_raise_AttributeError(MP_ERROR_TEXT("can't set attribute"));
         }
+        #endif
         if (attr == MP_QSTR___traceback__) {
             if (dest[1] == mp_const_none) {
                 self->traceback = (mp_obj_traceback_t *)&mp_const_empty_traceback_obj;
             } else {
                 if (!mp_obj_is_type(dest[1], &mp_type_traceback)) {
-                    mp_raise_TypeError(MP_ERROR_TEXT("invalid traceback"));
+                    mp_raise_TypeError_varg(MP_ERROR_TEXT("%q must be of type %q or None"), MP_QSTR___context__, MP_QSTR_traceback);
                 }
                 self->traceback = MP_OBJ_TO_PTR(dest[1]);
             }
             dest[0] = MP_OBJ_NULL; // indicate success
+        #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+        } else if (attr == MP_QSTR___cause__) {
+            if (dest[1] == mp_const_none) {
+                self->cause = NULL;
+            } else if (!mp_obj_is_type(dest[1], &mp_type_BaseException)) {
+                self->cause = dest[1];
+            } else {
+                mp_raise_TypeError_varg(MP_ERROR_TEXT("%q must be of type %q or None"), attr, MP_QSTR_BaseException);
+            }
+            self->suppress_context = true;
+            dest[0] = MP_OBJ_NULL; // indicate success
+        } else if (attr == MP_QSTR___context__) {
+            if (dest[1] == mp_const_none) {
+                self->context = NULL;
+            } else if (!mp_obj_is_type(dest[1], &mp_type_BaseException)) {
+                self->context = dest[1];
+            } else {
+                mp_raise_TypeError_varg(MP_ERROR_TEXT("%q must be of type %q or None"), attr, MP_QSTR_BaseException);
+            }
+            dest[0] = MP_OBJ_NULL; // indicate success
+        } else if (attr == MP_QSTR___suppress_context__) {
+            self->suppress_context = mp_obj_is_true(dest[1]);
+            dest[0] = MP_OBJ_NULL; // indicate success
+        #endif
         }
         return;
     }
@@ -240,6 +266,14 @@ void mp_obj_exception_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
         dest[0] = mp_obj_exception_get_value(self_in);
     } else if (attr == MP_QSTR___traceback__) {
         dest[0] = (self->traceback) ? MP_OBJ_FROM_PTR(self->traceback) : mp_const_none;
+    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+    } else if (attr == MP_QSTR___cause__) {
+        dest[0] = (self->cause) ? MP_OBJ_FROM_PTR(self->cause) : mp_const_none;
+    } else if (attr == MP_QSTR___context__) {
+        dest[0] = (self->context) ? MP_OBJ_FROM_PTR(self->context) : mp_const_none;
+    } else if (attr == MP_QSTR___suppress_context__) {
+        dest[0] = mp_obj_new_bool(self->suppress_context);
+    #endif
     #if MICROPY_CPYTHON_COMPAT
     } else if (mp_obj_is_subclass_fast(MP_OBJ_FROM_PTR(self->base.type), MP_OBJ_FROM_PTR(&mp_type_OSError))) {
         if (attr == MP_QSTR_errno) {

py/objexcept.h

@@ -34,6 +34,11 @@ typedef struct _mp_obj_exception_t {
     mp_obj_base_t base;
     mp_obj_tuple_t *args;
     mp_obj_traceback_t *traceback;
+    #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);

py/objgenerator.c

@@ -38,7 +38,12 @@
 #include "supervisor/shared/translate/translate.h"
 
 // Instance of GeneratorExit exception - needed by generator.close()
-const mp_obj_exception_t mp_const_GeneratorExit_obj = {{&mp_type_GeneratorExit}, (mp_obj_tuple_t *)&mp_const_empty_tuple_obj, (mp_obj_traceback_t *)&mp_const_empty_traceback_obj};
+#if MICROPY_CONST_GENERATOREXIT_OBJ
+const
+#else
+static
+#endif
+mp_obj_exception_t mp_static_GeneratorExit_obj = {{&mp_type_GeneratorExit}, (mp_obj_tuple_t *)&mp_const_empty_tuple_obj, (mp_obj_traceback_t *)&mp_const_empty_traceback_obj};
 
 /******************************************************************************/
 /* generator wrapper                                                          */
@@ -362,9 +367,19 @@ STATIC mp_obj_t gen_instance_throw(size_t n_args, const mp_obj_t *args) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(gen_instance_throw_obj, 2, 4, gen_instance_throw);
 
+static mp_obj_t generatorexit(void) {
+    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+    MP_STATIC_ASSERT(!MICROPY_CONST_GENERATOREXIT_OBJ);
+    mp_static_GeneratorExit_obj.context = NULL;
+    mp_static_GeneratorExit_obj.cause = NULL;
+    mp_static_GeneratorExit_obj.suppress_context = false;
+    #endif
+    return MP_OBJ_FROM_PTR(&mp_static_GeneratorExit_obj);
+}
+
 STATIC mp_obj_t gen_instance_close(mp_obj_t self_in) {
     mp_obj_t ret;
-    switch (mp_obj_gen_resume(self_in, mp_const_none, MP_OBJ_FROM_PTR(&mp_const_GeneratorExit_obj), &ret)) {
+    switch (mp_obj_gen_resume(self_in, mp_const_none, generatorexit(), &ret)) {
         case MP_VM_RETURN_YIELD:
             mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("generator ignored GeneratorExit"));
 

py/vm.c

@@ -183,6 +183,15 @@
 #define TRACE_TICK(current_ip, current_sp, is_exception)
 #endif // MICROPY_PY_SYS_SETTRACE
 
+STATIC mp_obj_t get_active_exception(mp_exc_stack_t *exc_sp, mp_exc_stack_t *exc_stack) {
+    for (mp_exc_stack_t *e = exc_sp; e >= exc_stack; --e) {
+        if (e->prev_exc != NULL) {
+            return MP_OBJ_FROM_PTR(e->prev_exc);
+        }
+    }
+    return MP_OBJ_NULL;
+}
+
 // fastn has items in reverse order (fastn[0] is local[0], fastn[-1] is local[1], etc)
 // sp points to bottom of stack which grows up
 // returns:
@@ -1129,13 +1138,7 @@ unwind_jump:;
                 ENTRY(MP_BC_RAISE_LAST): {
                     MARK_EXC_IP_SELECTIVE();
                     // search for the inner-most previous exception, to reraise it
-                    mp_obj_t obj = MP_OBJ_NULL;
-                    for (mp_exc_stack_t *e = exc_sp; e >= exc_stack; --e) {
-                        if (e->prev_exc != NULL) {
-                            obj = MP_OBJ_FROM_PTR(e->prev_exc);
-                            break;
-                        }
-                    }
+                    mp_obj_t obj = get_active_exception(exc_sp, exc_stack);
                     if (obj == MP_OBJ_NULL) {
                         obj = mp_obj_new_exception_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("no active exception to reraise"));
                     }
@@ -1145,14 +1148,30 @@ unwind_jump:;
                 ENTRY(MP_BC_RAISE_OBJ): {
                     MARK_EXC_IP_SELECTIVE();
                     mp_obj_t obj = mp_make_raise_obj(TOP());
+                    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                    mp_obj_t active_exception = get_active_exception(exc_sp, exc_stack);
+                    if (active_exception != MP_OBJ_NULL) {
+                        mp_store_attr(obj, MP_QSTR___context__, active_exception);
+                    }
+                    #endif
                     RAISE(obj);
                 }
 
                 ENTRY(MP_BC_RAISE_FROM): {
                     MARK_EXC_IP_SELECTIVE();
-                    mp_warning(NULL, "exception chaining not supported");
-                    sp--; // ignore (pop) "from" argument
+                    mp_obj_t cause = POP();
                     mp_obj_t obj = mp_make_raise_obj(TOP());
+                    #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                    // search for the inner-most previous exception, to chain it
+                    mp_obj_t active_exception = get_active_exception(exc_sp, exc_stack);
+                    if (active_exception != MP_OBJ_NULL) {
+                        mp_store_attr(obj, MP_QSTR___context__, active_exception);
+                    }
+                    mp_store_attr(obj, MP_QSTR___cause__, cause);
+                    #else
+                    (void)cause;
+                    mp_warning(NULL, "exception chaining not supported");
+                    #endif
                     RAISE(obj);
                 }
 
@@ -1391,7 +1410,10 @@ unwind_jump:;
             // - constant GeneratorExit object, because it's const
             // - exceptions re-raised by END_FINALLY
             // - exceptions re-raised explicitly by "raise"
-            if (nlr.ret_val != &mp_const_GeneratorExit_obj
+            if ( true
+                #if MICROPY_CONST_GENERATOREXIT_OBJ
+                && nlr.ret_val != &mp_static_GeneratorExit_obj
+                #endif
                 && *code_state->ip != MP_BC_END_FINALLY
                 && *code_state->ip != MP_BC_RAISE_LAST) {
                 const byte *ip = code_state->fun_bc->bytecode;
@@ -1434,10 +1456,19 @@ unwind_jump:;
                 // catch exception and pass to byte code
                 code_state->ip = exc_sp->handler;
                 mp_obj_t *sp = MP_TAGPTR_PTR(exc_sp->val_sp);
+                #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                mp_obj_t active_exception = get_active_exception(exc_sp, exc_stack);
+                #endif
                 // save this exception in the stack so it can be used in a reraise, if needed
                 exc_sp->prev_exc = nlr.ret_val;
+                mp_obj_t obj = MP_OBJ_FROM_PTR(nlr.ret_val);
+                #if MICROPY_CPYTHON_EXCEPTION_CHAIN
+                if (active_exception != MP_OBJ_NULL) {
+                    mp_store_attr(obj, MP_QSTR___context__, active_exception);
+                }
+                #endif
                 // push exception object so it can be handled by bytecode
-                PUSH(MP_OBJ_FROM_PTR(nlr.ret_val));
+                PUSH(obj);
                 code_state->sp = sp;
 
             #if MICROPY_STACKLESS