feat(output)!: consolidate errors in the human output format (closes e…

…ditorconfig-checker#359)

This changes the human output format to collect multiple identical error
messages on consecutive lines into one error message that list both the
starting and ending line.

This is still missing a properly written testcase, I so far only tested
locally.

pkg/error/error.go

@@ -10,8 +10,9 @@ import (
 
 // ValidationError represents one validation error
 type ValidationError struct {
-	LineNumber int
-	Message    error
+	LineNumber        int
+	Message           error
+	ConsecuitiveCount int
 }
 
 // ValidationErrors represents which errors occurred in a file
@@ -31,6 +32,44 @@ func GetErrorCount(errors []ValidationErrors) int {
 	return errorCount
 }
 
+func ConsolidateErrors(errors []ValidationError, config config.Config) []ValidationError {
+	var lineLessErrors []ValidationError
+	var errorsWithLines []ValidationError
+
+	// filter the errors, so we do not need to care about LineNumber == -1 in the loop below
+	for _, singleError := range errors {
+		if singleError.LineNumber == -1 {
+			lineLessErrors = append(lineLessErrors, singleError)
+		} else {
+			errorsWithLines = append(errorsWithLines, singleError)
+		}
+	}
+
+	config.Logger.Debug("sorted errors: %d with line number -1, %d with a line number", len(lineLessErrors), len(errorsWithLines))
+
+	var consolidatedErrors []ValidationError
+
+	// scan through the errors
+	for i := 0; i < len(errorsWithLines); i++ {
+		thisError := errorsWithLines[i]
+		config.Logger.Debug("investigating error %d(%s)", i, thisError.Message)
+		// scan through the errors after the current one
+		for j, nextError := range errorsWithLines[i+1:] {
+			config.Logger.Debug("comparing against error %d(%s)", j, nextError.Message)
+			if nextError.Message.Error() == thisError.Message.Error() {
+				thisError.ConsecuitiveCount++ // keep track of how many consecutive lines we've seen
+				i = i + j + 1                 // make sure the outer loop jumps over the consecutive errors we just found
+			} else {
+				break // if they are different errors we can stop comparing messages
+			}
+		}
+
+		consolidatedErrors = append(consolidatedErrors, thisError)
+	}
+
+	return append(lineLessErrors, consolidatedErrors...)
+}
+
 // PrintErrors prints the errors to the console
 func PrintErrors(errors []ValidationErrors, config config.Config) {
 	for _, fileErrors := range errors {
@@ -54,9 +93,13 @@ func PrintErrors(errors []ValidationErrors, config config.Config) {
 			} else {
 				// default: A human readable text format.
 				config.Logger.Warning(fmt.Sprintf("%s:", relativeFilePath))
-				for _, singleError := range fileErrors.Errors {
+				for _, singleError := range ConsolidateErrors(fileErrors.Errors, config) {
 					if singleError.LineNumber != -1 {
-						config.Logger.Error(fmt.Sprintf("\t%d: %s", singleError.LineNumber, singleError.Message))
+						if singleError.ConsecuitiveCount != 0 {
+							config.Logger.Error(fmt.Sprintf("\t%d-%d: %s", singleError.LineNumber, singleError.LineNumber+singleError.ConsecuitiveCount, singleError.Message))
+						} else {
+							config.Logger.Error(fmt.Sprintf("\t%d: %s", singleError.LineNumber, singleError.Message))
+						}
 					} else {
 						config.Logger.Error(fmt.Sprintf("\t%s", singleError.Message))
 					}