41 lines
1.0 KiB
Go
41 lines
1.0 KiB
Go
package json
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import (
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"bytes"
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"encoding/json"
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"fmt"
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)
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// Unmarshal is wrapper around json.Unmarshal that returns user-friendly
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// errors when there are syntax errors.
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func Unmarshal(data []byte, i interface{}) error {
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err := json.Unmarshal(data, i)
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if err != nil {
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syntaxErr, ok := err.(*json.SyntaxError)
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if !ok {
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return err
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}
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// We have a syntax error. Extract out the line number and friends.
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// https://groups.google.com/forum/#!topic/golang-nuts/fizimmXtVfc
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newline := []byte{'\x0a'}
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// Calculate the start/end position of the line where the error is
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start := bytes.LastIndex(data[:syntaxErr.Offset], newline) + 1
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end := len(data)
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if idx := bytes.Index(data[start:], newline); idx >= 0 {
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end = start + idx
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}
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// Count the line number we're on plus the offset in the line
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line := bytes.Count(data[:start], newline) + 1
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pos := int(syntaxErr.Offset) - start - 1
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err = fmt.Errorf("Error in line %d, char %d: %s\n%s",
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line, pos, syntaxErr, data[start:end])
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return err
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}
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return nil
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}
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