Implement `mrb_protect`, `mrb_ensure`, `mrb_rescue`, `mrb_rescue_exceptions`.

(`mrb_rescue_exceptions` is mruby implementation of `rb_rescue2`.)
Closes #2844, closes #2837.

include/mruby/error.h

@@ -29,6 +29,14 @@ MRB_API mrb_noreturn void mrb_no_method_error(mrb_state *mrb, mrb_sym id, mrb_va
 /* declaration for fail method */
 MRB_API mrb_value mrb_f_raise(mrb_state*, mrb_value);
 
+MRB_API mrb_value mrb_protect(mrb_state *mrb, mrb_func_t body, mrb_value data, mrb_bool *state);
+MRB_API mrb_value mrb_ensure(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
+                             mrb_func_t ensure, mrb_value e_data);
+MRB_API mrb_value mrb_rescue(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
+                             mrb_func_t rescue, mrb_value r_data);
+MRB_API mrb_value mrb_rescue_exceptions(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
+                                        mrb_func_t rescue, mrb_value r_data, ...);
+
 #if defined(__cplusplus)
 }  /* extern "C" { */
 #endif

mrbgems/mruby-error/mrbgem.rake

+MRuby::Gem::Specification.new('mruby-error') do |spec|
+  spec.license = 'MIT'
+  spec.author  = 'mruby developers'
+  spec.summary = 'extensional error handling'
+
+  if build.cxx_abi_enabled?
+    @objs << build.compile_as_cxx("#{spec.dir}/src/exception.c", "#{spec.build_dir}/src/exception.cxx")
+    @objs.delete_if { |v| v == objfile("#{spec.build_dir}/src/exception") }
+  end
+end

mrbgems/mruby-error/src/exception.c

+#include <stdarg.h>
+#include "mruby.h"
+#include "mruby/throw.h"
+#include "mruby/error.h"
+
+MRB_API mrb_value
+mrb_protect(mrb_state *mrb, mrb_func_t body, mrb_value data, mrb_bool *state)
+{
+  struct mrb_jmpbuf *prev_jmp = mrb->jmp;
+  struct mrb_jmpbuf c_jmp;
+  mrb_value result = mrb_nil_value();
+
+  if (state) { *state = FALSE; }
+
+  MRB_TRY(&c_jmp) {
+    mrb->jmp = &c_jmp;
+    result = body(mrb, data);
+    mrb->jmp = prev_jmp;
+  } MRB_CATCH(&c_jmp) {
+    mrb->jmp = prev_jmp;
+    mrb->exc = NULL;
+    if (state) { *state = TRUE; }
+  } MRB_END_EXC(&c_jmp);
+
+  mrb_gc_protect(mrb, result);
+  return result;
+}
+
+MRB_API mrb_value
+mrb_ensure(mrb_state *mrb, mrb_func_t body, mrb_value b_data, mrb_func_t ensure, mrb_value e_data)
+{
+  struct mrb_jmpbuf *prev_jmp = mrb->jmp;
+  struct mrb_jmpbuf c_jmp;
+  mrb_value result;
+
+  MRB_TRY(&c_jmp) {
+    mrb->jmp = &c_jmp;
+    result = body(mrb, b_data);
+    mrb->jmp = prev_jmp;
+  } MRB_CATCH(&c_jmp) {
+    mrb->jmp = prev_jmp;
+    ensure(mrb, e_data);
+    MRB_THROW(mrb->jmp); /* rethrow catched exceptions */
+  } MRB_END_EXC(&c_jmp);
+
+  ensure(mrb, e_data);
+  mrb_gc_protect(mrb, result);
+  return result;
+}
+
+MRB_API mrb_value
+mrb_rescue(mrb_state *mrb, mrb_func_t body, mrb_value b_data,
+           mrb_func_t rescue, mrb_value r_data)
+{
+  return mrb_rescue_exceptions(mrb, body, b_data, rescue, r_data, mrb->eStandardError_class, NULL);
+}
+
+MRB_API mrb_value
+mrb_rescue_exceptions(mrb_state *mrb, mrb_func_t body, mrb_value b_data, mrb_func_t rescue, mrb_value r_data, ...)
+{
+  struct mrb_jmpbuf *prev_jmp = mrb->jmp;
+  struct mrb_jmpbuf c_jmp;
+  mrb_value result;
+  va_list excs;
+  struct RClass *cls;
+  mrb_bool error_matched = FALSE;
+
+  MRB_TRY(&c_jmp) {
+    mrb->jmp = &c_jmp;
+    result = body(mrb, b_data);
+    mrb->jmp = prev_jmp;
+  } MRB_CATCH(&c_jmp) {
+    mrb->jmp = prev_jmp;
+
+    va_start(excs, r_data);
+    while((cls = va_arg(excs, struct RClass*))) {
+      if (mrb_obj_is_kind_of(mrb, mrb_obj_value(mrb->exc), cls)) {
+        error_matched = TRUE;
+        break;
+      }
+    }
+    va_end(excs);
+
+    if (!error_matched) { MRB_THROW(mrb->jmp); }
+
+    mrb->exc = NULL;
+    result = rescue(mrb, r_data);
+  } MRB_END_EXC(&c_jmp);
+
+  mrb_gc_protect(mrb, result);
+  return result;
+}
+
+void
+mrb_mruby_error_gem_init(mrb_state *mrb)
+{
+}
+
+void
+mrb_mruby_error_gem_final(mrb_state *mrb)
+{
+}

mrbgems/mruby-error/test/exception.c

+#include "mruby.h"
+#include "mruby/error.h"
+#include "mruby/array.h"
+
+static mrb_value
+protect_cb(mrb_state *mrb, mrb_value b)
+{
+  return mrb_yield_argv(mrb, b, 0, NULL);
+}
+
+static mrb_value
+run_protect(mrb_state *mrb, mrb_value self)
+{
+  mrb_value b;
+  mrb_value ret[2];
+  mrb_bool state;
+  mrb_get_args(mrb, "&", &b);
+  ret[0] = mrb_protect(mrb, protect_cb, b, &state);
+  ret[1] = mrb_bool_value(state);
+  return mrb_ary_new_from_values(mrb, 2, ret);
+}
+
+static mrb_value
+run_ensure(mrb_state *mrb, mrb_value self)
+{
+  mrb_value b, e;
+  mrb_get_args(mrb, "oo", &b, &e);
+  return mrb_ensure(mrb, protect_cb, b, protect_cb, e);
+}
+
+static mrb_value
+run_rescue(mrb_state *mrb, mrb_value self)
+{
+  mrb_value b, r;
+  mrb_get_args(mrb, "oo", &b, &r);
+  return mrb_rescue(mrb, protect_cb, b, protect_cb, r);
+}
+
+static mrb_value
+run_rescue_exceptions(mrb_state *mrb, mrb_value self)
+{
+  mrb_value b, r;
+  mrb_get_args(mrb, "oo", &b, &r);
+  return mrb_rescue_exceptions(mrb, protect_cb, b, protect_cb, r, E_TYPE_ERROR, NULL);
+}
+
+void
+mrb_mruby_error_gem_test(mrb_state *mrb)
+{
+  struct RClass *cls;
+
+  cls = mrb_define_class(mrb, "ExceptionTest", mrb->object_class);
+  mrb_define_module_function(mrb, cls, "mrb_protect", run_protect, MRB_ARGS_NONE() | MRB_ARGS_BLOCK());
+  mrb_define_module_function(mrb, cls, "mrb_ensure", run_ensure, MRB_ARGS_REQ(2));
+  mrb_define_module_function(mrb, cls, "mrb_rescue", run_rescue, MRB_ARGS_REQ(2));
+  mrb_define_module_function(mrb, cls, "mrb_rescue_exceptions", run_rescue_exceptions, MRB_ARGS_REQ(2));
+}

mrbgems/mruby-error/test/exception.rb

+assert 'mrb_protect' do
+  assert_equal ['test', false] do
+    ExceptionTest.mrb_protect { 'test' }
+  end
+  assert_equal [nil, true] do
+    ExceptionTest.mrb_protect { raise 'test' }
+  end
+end
+
+assert 'mrb_ensure' do
+  a = false
+  assert_equal 'test' do
+    ExceptionTest.mrb_ensure Proc.new { 'test' }, Proc.new { a = true }
+  end
+  assert_true a
+
+  a = false
+  assert_raise RuntimeError do
+    ExceptionTest.mrb_ensure Proc.new { raise 'test' }, Proc.new { a = true }
+  end
+  assert_true a
+end
+
+assert 'mrb_rescue' do
+  assert_equal 'test' do
+    ExceptionTest.mrb_rescue Proc.new { 'test' }, Proc.new {}
+  end
+
+  class CustomExp < Exception
+  end
+
+  assert_raise CustomExp do
+    ExceptionTest.mrb_rescue Proc.new { raise CustomExp.new 'test' }, Proc.new { 'rescue' }
+  end
+
+  assert_equal 'rescue' do
+    ExceptionTest.mrb_rescue Proc.new { raise 'test' }, Proc.new { 'rescue' }
+  end
+end
+
+assert 'mrb_rescue_exceptions' do
+  assert_equal 'test' do
+    ExceptionTest.mrb_rescue_exceptions Proc.new { 'test' }, Proc.new {}
+  end
+
+  assert_raise RangeError do
+    ExceptionTest.mrb_rescue_exceptions Proc.new { raise RangeError.new 'test' }, Proc.new { 'rescue' }
+  end
+
+  assert_equal 'rescue' do
+    ExceptionTest.mrb_rescue_exceptions Proc.new { raise TypeError.new 'test' }, Proc.new { 'rescue' }
+  end
+end