inancgumus/learngo · error

missing fields: %v

Error message

missing fields: %v

What it means

parse splits a log line with strings.Fields and requires exactly 3 fields: domain, visits, and time spent. Any other count returns this error listing the fields actually found, signaling the line doesn't match the expected 'domain visits timespent' format.

Source

Thrown at logparser/testing/report/result.go:42

	Visits    int    `json:"visits"`
	TimeSpent int    `json:"time_spent"`
	// add more metrics if needed
}

// add adds the metrics of another Result to itself and returns a new Result
func (r Result) add(other Result) Result {
	return Result{
		Domain:    r.Domain,
		Visits:    r.Visits + other.Visits,
		TimeSpent: r.TimeSpent + other.TimeSpent,
	}
}

// parse parses a single log line
func parse(line string) (r Result, err error) {
	fields := strings.Fields(line)
	if len(fields) != 3 {
		return r, fmt.Errorf("missing fields: %v", fields)
	}

	f := new(field)
	r.Domain = fields[0]
	r.Visits = f.atoi("visits", fields[1])
	r.TimeSpent = f.atoi("time spent", fields[2])
	return r, f.err
}

// field helps for field parsing
type field struct{ err error }

func (f *field) atoi(name, val string) int {
	n, err := strconv.Atoi(val)
	if n < 0 || err != nil {
		f.err = fmt.Errorf("incorrect %s: %q", name, val)
	}
	return n

View on GitHub (pinned to 3c475a78e5)

Solutions

1. Normalize the input so every line has exactly: domain visits timeSpent
2. Skip empty/whitespace-only lines before calling parse
3. Give a clearer message, e.g. expected 3 fields, got N, with the raw line

Example fix

// before
if len(fields) != 3 {
    return r, fmt.Errorf("missing fields: %v", fields)
}
// after
if len(fields) != 3 {
    return r, fmt.Errorf("expected 3 fields (domain visits timeSpent), got %d: %q", len(fields), line)
}

func validResultLine(line string) bool {
    fs := strings.Fields(line)
    return len(fs) == 3
}
// call before parse: if !validResultLine(line) { skip }

func hasThreeFields(line string) bool {
    return len(strings.Fields(line)) == 3
}

r, err := parse(line)
if err != nil {
    if strings.HasPrefix(err.Error(), "missing fields") {
        log.Printf("skipping malformed line %q: %v", line, err)
        continue
    }
    return err
}

When it happens

Trigger: Calling parse (from main, via the report parser) with a line containing 0, 1, 2, or 4+ whitespace-separated tokens, e.g. a blank line or a line missing the time-spent value.

Common situations: Hand-edited log files, CSV/TSV lines pasted into a space-separated log, trailing multi-space entries that Fields collapses, or header/footer lines in exported logs.

Related errors

• invalid number
• Please provide a valid number
• line %d: %v
• line #%d: %s
• incorrect %s: %q

AI-assisted analysis of inancgumus/learngo@3c475a78e5 (2026-09-02). Data as JSON: /api/errors/6abb053d1d165cad. Report an issue: GitHub.