exc += XRun() - utility to run a function which returns regular error, and...

exc += XRun() - utility to run a function which returns regular error, and raise exception if error is not nil

This might be frequently needed in tests, possibly with some kind of
"apply" syntatic sugar.

Complements 486ede30 (exc += Runx() - utility to run a function and
translate caught exception to regular error)

exc/error.go

@@ -190,3 +190,9 @@ func Runx(xf func()) (err error) {
 	xf()
 	return
 }
+
+// run a function which returns regular error, and raise exception if error is not nil.
+func XRun(f func() error) {
+	err := f()
+	Raiseif(err)
+}

exc/error_test.go

@@ -167,3 +167,24 @@ func TestRunx(t *testing.T) {
 		}
 	}
 }
+
+func TestXRun(t *testing.T) {
+	var tests = []struct { f func() error; wanterr string } {
+		{func() error { return nil },			""},
+		{func() error { return errors.New("abc") },	"X abc"},
+	}
+
+	for _, tt := range tests {
+		errStr := ""
+		func() {
+			defer Catch(func(e *Error) {
+				errStr = "X " + e.Error()
+			})
+			XRun(tt.f)
+		}()
+
+		if errStr != tt.wanterr {
+			t.Errorf("xrun(%v) -> %q  ; want %q", funcname(tt.f), errStr, tt.wanterr)
+		}
+	}
+}