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|
package reader
import (
"bufio"
"bytes"
"encoding/json"
"io"
"strings"
"time"
)
// LineReader is an interface to read lines with optional Metadata.
type LineReader interface {
ReadLine() (string, *Metadata, error)
}
// Metadata contains metadata that belongs to a line.
type Metadata struct {
Package string
}
// LimitedLineReader reads lines from an io.Reader object with a configurable
// line size limit. Lines exceeding the limit will be truncated, but read
// completely from the underlying io.Reader.
type LimitedLineReader struct {
r *bufio.Reader
limit int
}
var _ LineReader = &LimitedLineReader{}
// NewLimitedLineReader returns a LimitedLineReader to read lines from r with a
// maximum line size of limit.
func NewLimitedLineReader(r io.Reader, limit int) *LimitedLineReader {
return &LimitedLineReader{r: bufio.NewReader(r), limit: limit}
}
// ReadLine returns the next line from the underlying reader. The length of the
// line will not exceed the configured limit. ReadLine either returns a line or
// it returns an error, never both.
func (r *LimitedLineReader) ReadLine() (string, *Metadata, error) {
line, isPrefix, err := r.r.ReadLine()
if err != nil {
return "", nil, err
}
if !isPrefix {
return string(line), nil, nil
}
// Line is incomplete, keep reading until we reach the end of the line.
var buf bytes.Buffer
buf.Write(line) // ignore err, always nil
for isPrefix {
line, isPrefix, err = r.r.ReadLine()
if err != nil {
return "", nil, err
}
if buf.Len() >= r.limit {
// Stop writing to buf if we exceed the limit. We continue reading
// however to make sure we consume the entire line.
continue
}
buf.Write(line) // ignore err, always nil
}
if buf.Len() > r.limit {
buf.Truncate(r.limit)
}
return buf.String(), nil, nil
}
// Event represents a JSON event emitted by `go test -json`.
type Event struct {
Time time.Time
Action string
Package string
Test string
Elapsed float64 // seconds
Output string
}
// JSONEventReader reads JSON events from an io.Reader object.
type JSONEventReader struct {
r *LimitedLineReader
}
var _ LineReader = &JSONEventReader{}
// jsonLineLimit is the maximum size of a single JSON line emitted by `go test
// -json`.
const jsonLineLimit = 64 * 1024
// NewJSONEventReader returns a JSONEventReader to read the data in JSON
// events from r.
func NewJSONEventReader(r io.Reader) *JSONEventReader {
return &JSONEventReader{NewLimitedLineReader(r, jsonLineLimit)}
}
// ReadLine returns the next line from the underlying reader.
func (r *JSONEventReader) ReadLine() (string, *Metadata, error) {
for {
line, _, err := r.r.ReadLine()
if err != nil {
return "", nil, err
}
if len(line) == 0 || line[0] != '{' {
return line, nil, nil
}
event := &Event{}
if err := json.Unmarshal([]byte(line), event); err != nil {
return "", nil, err
}
if event.Output == "" {
// Skip events without output
continue
}
return strings.TrimSuffix(event.Output, "\n"), &Metadata{Package: event.Package}, nil
}
}
|
