SoMsg proof of concept.

Adds a variant of So() that allows you to specify a message that is
reported on error.

convey/context.go

@@ -177,6 +177,17 @@ func (ctx *context) So(actual interface{}, assert assertion, expected ...interfa
 	}
 }
 
+func (ctx *context) SoMsg(msg string, actual interface{}, assert assertion, expected ...interface{}) {
+	if result := assert(actual, expected...); result == assertionSuccess {
+		ctx.assertionReport(reporting.NewSuccessReport())
+		return
+	} else {
+		ctx.reporter.Enter(reporting.NewScopeReport(msg))
+		defer ctx.reporter.Exit()
+		ctx.assertionReport(reporting.NewFailureReport(result))
+	}
+}
+
 func (ctx *context) Reset(action func()) {
 	/* TODO: Failure mode configuration */
 	ctx.resets = append(ctx.resets, action)

convey/doc.go

@@ -125,6 +125,10 @@ func So(actual interface{}, assert assertion, expected ...interface{}) {
 	mustGetCurrentContext().So(actual, assert, expected...)
 }
 
+func SoMsg(msg string, actual interface{}, assert assertion, expected ...interface{}) {
+	mustGetCurrentContext().SoMsg(msg, actual, assert, expected...)
+}
+
 // SkipSo is analogous to So except that the assertion that would have been passed
 // to So is not executed and the reporter is notified that the assertion was skipped.
 func SkipSo(stuff ...interface{}) {