pavlo/heatit

package utils

import (
    "fmt"
    "log"
    "regexp"
    "strconv"
    "strings"
)

const (
    regularLineFormat = "%v:\t\t%v\n"
    errorLineFormat   = "%v: =>\t\t%v\n"
    newLine           = "\n"
)

var currentLineRegexp, _ = regexp.Compile("line (\\d+):")

// DescribeUnmarshalError pretty prints the error that occured when it attempted
// to convert the result to YAML.
//
// This means that it generated a content that can not be parsed into YAML. This certainly is
// developer's issue and our job now is to help the developer out as much as possible.
// The `yaml` library prints out a error message with the line number in the content
// that it thinks had the error. So we dump the content line by line with line numbers
// printed at the left for easier navigation.
// See https://github.com/pavlo/heatit/issues/7
func DescribeUnmarshalError(data string, err error) {
    // Message usually looks like this:
    // "yaml: line 1: mapping values are not allowed in this context"
    msg := err.Error()

    lineNum := -1
    matches := currentLineRegexp.FindStringSubmatch(msg)

    if len(matches) == 2 {
        lineNum, _ = strconv.Atoi(matches[1])
    }

    log.Println("Failed to Unmarshal resulting data to YAML!")
    log.Printf("%v\n", err)

    for ind, str := range strings.Split(data, newLine) {
        format := regularLineFormat
        if lineNum == ind {
            format = errorLineFormat
        }
        fmt.Printf(format, ind, str)
    }
}