parser/gotest: Create JSONEventReader in internal reader package

The JSONEventReader implements reading lines with metadata and replaces
the gotest.jsonReader struct.

Author: jstemmer

parser/gotest/internal/reader/reader.go

@@ -3,7 +3,10 @@ package reader
 import (
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"io"
+	"strings"
+	"time"
 )
 
 // LineReader is an interface to read lines with optional Metadata.
@@ -68,3 +71,52 @@ func (r *LimitedLineReader) ReadLine() (string, *Metadata, error) {
 	}
 	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
+	}
+}

parser/gotest/internal/reader/reader_test.go

@@ -5,6 +5,8 @@ import (
 	"io"
 	"strings"
 	"testing"
+
+	"github.com/google/go-cmp/cmp"
 )
 
 const testingLimit = 4 * 1024 * 1024
@@ -66,3 +68,34 @@ func TestLimitedLineReader(t *testing.T) {
 		})
 	}
 }
+
+func TestJSONEventReader(t *testing.T) {
+	input := `some other output
+{"Time":"2019-10-09T00:00:00.708139047+00:00","Action":"output","Package":"package/name/ok","Test":"TestOK"}
+{"Time":"2019-10-09T00:00:00.708139047+00:00","Action":"output","Package":"package/name/ok","Test":"TestOK","Output":"=== RUN   TestOK\n"}
+`
+	want := []struct {
+		line     string
+		metadata *Metadata
+	}{
+		{"some other output", nil},
+		{"=== RUN   TestOK", &Metadata{Package: "package/name/ok"}},
+	}
+
+	r := NewJSONEventReader(strings.NewReader(input))
+	for i := 0; i < len(want); i++ {
+		line, metadata, err := r.ReadLine()
+		if err == io.EOF {
+			return
+		} else if err != nil {
+			t.Fatalf("ReadLine() returned error %v", err)
+		}
+
+		if diff := cmp.Diff(want[i].line, line); diff != "" {
+			t.Errorf("ReadLine() returned incorrect line, diff (-want, +got):\n%s\n", diff)
+		}
+		if diff := cmp.Diff(want[i].metadata, metadata); diff != "" {
+			t.Errorf("ReadLine() Returned incorrect metadata, diff (-want, +got):\n%s\n", diff)
+		}
+	}
+}

parser/gotest/json.go

@@ -1,12 +1,10 @@
 package gotest
 
 import (
-	"bufio"
-	"encoding/json"
 	"io"
-	"time"
 
 	"github.com/jstemmer/go-junit-report/v2/gtr"
+	"github.com/jstemmer/go-junit-report/v2/parser/gotest/internal/reader"
 )
 
 // NewJSONParser returns a new Go test json output parser.
@@ -22,56 +20,10 @@ type JSONParser struct {
 // Parse parses Go test json output from the given io.Reader r and returns
 // gtr.Report.
 func (p *JSONParser) Parse(r io.Reader) (gtr.Report, error) {
-	return p.gp.Parse(newJSONReader(r))
+	return p.gp.parse(reader.NewJSONEventReader(r))
 }
 
 // Events returns the events created by the parser.
 func (p *JSONParser) Events() []Event {
 	return p.gp.Events()
 }
-
-type jsonEvent struct {
-	Time    time.Time
-	Action  string
-	Package string
-	Test    string
-	Elapsed float64 // seconds
-	Output  string
-}
-
-type jsonReader struct {
-	r   *bufio.Reader
-	buf []byte
-}
-
-func newJSONReader(reader io.Reader) *jsonReader {
-	return &jsonReader{r: bufio.NewReader(reader)}
-}
-
-func (j *jsonReader) Read(p []byte) (int, error) {
-	var err error
-	for len(j.buf) == 0 {
-		j.buf, err = j.readNextLine()
-		if err != nil {
-			return 0, err
-		}
-	}
-	n := copy(p, j.buf)
-	j.buf = j.buf[n:]
-	return n, nil
-}
-
-func (j jsonReader) readNextLine() ([]byte, error) {
-	line, err := j.r.ReadBytes('\n')
-	if err != nil {
-		return nil, err
-	}
-	if len(line) == 0 || line[0] != '{' {
-		return line, nil
-	}
-	var event jsonEvent
-	if err := json.Unmarshal(line, &event); err != nil {
-		return nil, err
-	}
-	return []byte(event.Output), nil
-}