feat: improve the regrading utilities

majorityjudgment.go

@@ -103,9 +103,9 @@ func (mj *MajorityJudgment) ComputeScore(tally *ProposalTally, favorContestation
 		score += fmt.Sprintf("%0"+fmt.Sprintf("%d", amountOfDigitsForGrade)+"d", analysis.MedianGrade)
 		// fixme: BAD → uint64 to int conversion — either move to int everywhere, or use whatever bigint Go has
 		score += fmt.Sprintf("%0"+fmt.Sprintf("%d", amountOfDigitsForAdhesionScore)+"d", int(amountOfJudgments)+int(analysis.SecondGroupSize)*analysis.SecondGroupSign)
-		err := mutatedTally.RegradeJudgments(analysis.MedianGrade, analysis.SecondMedianGrade)
-		if nil != err {
-			return "", err
+		regradingErr := mutatedTally.RegradeJudgments(analysis.MedianGrade, analysis.SecondMedianGrade)
+		if nil != regradingErr {
+			return "", regradingErr
 		}
 	}
 

tally.go

@@ -39,6 +39,10 @@ func (proposalTally *ProposalTally) CountAvailableGrades() (_ uint8) {
 
 // This mutates the proposalTally.
 func (proposalTally *ProposalTally) RegradeJudgments(fromGrade uint8, intoGrade uint8) (err error) {
+	if fromGrade == intoGrade {
+		return nil
+	}
+
 	amountOfGrades := proposalTally.CountAvailableGrades()
 	if fromGrade >= amountOfGrades {
 		return fmt.Errorf("RegradeJudgments() fromGrade is too high")

tally_test.go

@@ -18,6 +18,19 @@ func TestProposalTally_RegradeJudgments(t *testing.T) {
 	assert.Equal(t, uint64(8), proposalTally.Tally[6])
 }
 
+func TestProposalTally_RegradeJudgmentsIntoSelf(t *testing.T) {
+	proposalTally := ProposalTally{Tally: []uint64{1, 2, 3, 4, 5, 6, 7}}
+	err := proposalTally.RegradeJudgments(2, 2)
+	assert.NoError(t, err, "Regrading should succeed")
+	assert.Equal(t, uint64(1), proposalTally.Tally[0])
+	assert.Equal(t, uint64(2), proposalTally.Tally[1])
+	assert.Equal(t, uint64(3), proposalTally.Tally[2])
+	assert.Equal(t, uint64(4), proposalTally.Tally[3])
+	assert.Equal(t, uint64(5), proposalTally.Tally[4])
+	assert.Equal(t, uint64(6), proposalTally.Tally[5])
+	assert.Equal(t, uint64(7), proposalTally.Tally[6])
+}
+
 func TestProposalTally_RegradeJudgments_Failure1(t *testing.T) {
 	proposalTally := ProposalTally{Tally: []uint64{1, 2, 3, 4, 5, 6, 7}}
 	err := proposalTally.RegradeJudgments(0, 60)