Avoid spurious [] on JSON output in some cases (#1528)

* JSON empty vs `[]` handling [WIP]

* unit-test mods

pkg/input/record_reader_json.go

@@ -17,6 +17,8 @@ import (
 type RecordReaderJSON struct {
 	readerOptions   *cli.TReaderOptions
 	recordsPerBatch int64 // distinct from readerOptions.RecordsPerBatch for join/repl
+	// XXX 1513
+	sawBrackets bool
 }
 
 func NewRecordReaderJSON(
@@ -65,6 +67,7 @@ func (reader *RecordReaderJSON) Read(
 			}
 		}
 	}
+	context.JSONHadBrackets = reader.sawBrackets
 	readerChannel <- types.NewEndOfStreamMarkerList(&context)
 }
 
@@ -137,6 +140,9 @@ func (reader *RecordReaderJSON) processHandle(
 			}
 
 		} else if mlrval.IsArray() {
+
+			reader.sawBrackets = true
+
 			records := mlrval.GetArray()
 			if records == nil {
 				errorChannel <- fmt.Errorf("internal coding error detected in JSON record-reader")

pkg/output/channel_writer.go

@@ -66,6 +66,7 @@ func channelWriterHandleBatch(
 
 		if !recordAndContext.EndOfStream {
 			record := recordAndContext.Record
+			context := &recordAndContext.Context
 
 			// XXX more
 			// XXX also make sure this results in exit 1 & goroutine cleanup
@@ -94,7 +95,7 @@ func channelWriterHandleBatch(
 			}
 
 			if record != nil {
-				err := recordWriter.Write(record, bufferedOutputStream, outputIsStdout)
+				err := recordWriter.Write(record, context, bufferedOutputStream, outputIsStdout)
 				if err != nil {
 					fmt.Fprintf(os.Stderr, "mlr: %v\n", err)
 					return true, true
@@ -115,7 +116,8 @@ func channelWriterHandleBatch(
 			// queued up. For example, PPRINT needs to see all same-schema
 			// records before printing any, since it needs to compute max width
 			// down columns.
-			err := recordWriter.Write(nil, bufferedOutputStream, outputIsStdout)
+			context := &recordAndContext.Context
+			err := recordWriter.Write(nil, context, bufferedOutputStream, outputIsStdout)
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "mlr: %v\n", err)
 				return true, true

pkg/output/record_writer.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 // IRecordWriter is the abstract interface for all record-writers.  They are
@@ -18,6 +19,7 @@ import (
 type IRecordWriter interface {
 	Write(
 		outrec *mlrval.Mlrmap,
+		context *types.Context,
 		bufferedOutputStream *bufio.Writer,
 		outputIsStdout bool,
 	) error

pkg/output/record_writer_csv.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterCSV struct {
@@ -41,6 +42,7 @@ func NewRecordWriterCSV(writerOptions *cli.TWriterOptions) (*RecordWriterCSV, er
 
 func (writer *RecordWriterCSV) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_csvlite.go

@@ -7,6 +7,7 @@ import (
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterCSVLite struct {
@@ -27,6 +28,7 @@ func NewRecordWriterCSVLite(writerOptions *cli.TWriterOptions) (*RecordWriterCSV
 
 func (writer *RecordWriterCSVLite) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_dkvp.go

@@ -6,6 +6,7 @@ import (
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterDKVP struct {
@@ -20,6 +21,7 @@ func NewRecordWriterDKVP(writerOptions *cli.TWriterOptions) (*RecordWriterDKVP,
 
 func (writer *RecordWriterDKVP) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_json.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 // ----------------------------------------------------------------
@@ -17,7 +18,7 @@ type RecordWriterJSON struct {
 	jvQuoteAll     bool
 
 	// State:
-	onFirst bool
+	wroteAnyRecords bool
 }
 
 // ----------------------------------------------------------------
@@ -27,16 +28,17 @@ func NewRecordWriterJSON(writerOptions *cli.TWriterOptions) (*RecordWriterJSON,
 		jsonFormatting = mlrval.JSON_MULTILINE
 	}
 	return &RecordWriterJSON{
-		writerOptions:  writerOptions,
-		jsonFormatting: jsonFormatting,
-		jvQuoteAll:     writerOptions.JVQuoteAll,
-		onFirst:        true,
+		writerOptions:   writerOptions,
+		jsonFormatting:  jsonFormatting,
+		jvQuoteAll:      writerOptions.JVQuoteAll,
+		wroteAnyRecords: false,
 	}, nil
 }
 
 // ----------------------------------------------------------------
 func (writer *RecordWriterJSON) Write(
 	outrec *mlrval.Mlrmap,
+	context *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {
@@ -45,9 +47,9 @@ func (writer *RecordWriterJSON) Write(
 	}
 
 	if writer.writerOptions.WrapJSONOutputInOuterList {
-		writer.writeWithListWrap(outrec, bufferedOutputStream, outputIsStdout)
+		writer.writeWithListWrap(outrec, context, bufferedOutputStream, outputIsStdout)
 	} else {
-		writer.writeWithoutListWrap(outrec, bufferedOutputStream, outputIsStdout)
+		writer.writeWithoutListWrap(outrec, context, bufferedOutputStream, outputIsStdout)
 	}
 	return nil
 }
@@ -55,11 +57,12 @@ func (writer *RecordWriterJSON) Write(
 // ----------------------------------------------------------------
 func (writer *RecordWriterJSON) writeWithListWrap(
 	outrec *mlrval.Mlrmap,
+	context *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) {
 	if outrec != nil { // Not end of record stream
-		if writer.onFirst {
+		if !writer.wroteAnyRecords {
 			bufferedOutputStream.WriteString("[\n")
 		}
 
@@ -71,25 +74,32 @@ func (writer *RecordWriterJSON) writeWithListWrap(
 			os.Exit(1)
 		}
 
-		if !writer.onFirst {
+		if writer.wroteAnyRecords {
 			bufferedOutputStream.WriteString(",\n")
 		}
 
 		bufferedOutputStream.WriteString(s)
 
-		writer.onFirst = false
+		writer.wroteAnyRecords = true
 
 	} else { // End of record stream
-		if writer.onFirst { // zero records in the entire output stream
-			bufferedOutputStream.WriteString("[")
+
+		if !writer.wroteAnyRecords {
+			if context.JSONHadBrackets {
+				bufferedOutputStream.WriteString("[")
+				bufferedOutputStream.WriteString("\n]\n")
+			}
+		} else {
+			bufferedOutputStream.WriteString("\n]\n")
 		}
-		bufferedOutputStream.WriteString("\n]\n")
+
 	}
 }
 
 // ----------------------------------------------------------------
 func (writer *RecordWriterJSON) writeWithoutListWrap(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) {

pkg/output/record_writer_markdown.go

@@ -7,6 +7,7 @@ import (
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterMarkdown struct {
@@ -29,6 +30,7 @@ func NewRecordWriterMarkdown(writerOptions *cli.TWriterOptions) (*RecordWriterMa
 // ----------------------------------------------------------------
 func (writer *RecordWriterMarkdown) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_nidx.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterNIDX struct {
@@ -19,6 +20,7 @@ func NewRecordWriterNIDX(writerOptions *cli.TWriterOptions) (*RecordWriterNIDX,
 
 func (writer *RecordWriterNIDX) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_pprint.go

@@ -10,6 +10,7 @@ import (
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterPPRINT struct {
@@ -35,6 +36,7 @@ func NewRecordWriterPPRINT(writerOptions *cli.TWriterOptions) (*RecordWriterPPRI
 // ----------------------------------------------------------------
 func (writer *RecordWriterPPRINT) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_tsv.go

@@ -9,6 +9,7 @@ import (
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/lib"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 type RecordWriterTSV struct {
@@ -35,6 +36,7 @@ func NewRecordWriterTSV(writerOptions *cli.TWriterOptions) (*RecordWriterTSV, er
 
 func (writer *RecordWriterTSV) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/output/record_writer_xtab.go

@@ -8,6 +8,7 @@ import (
 	"github.com/johnkerl/miller/pkg/cli"
 	"github.com/johnkerl/miller/pkg/colorizer"
 	"github.com/johnkerl/miller/pkg/mlrval"
+	"github.com/johnkerl/miller/pkg/types"
 )
 
 // ----------------------------------------------------------------
@@ -43,6 +44,7 @@ func NewRecordWriterXTAB(writerOptions *cli.TWriterOptions) (*RecordWriterXTAB,
 
 func (writer *RecordWriterXTAB) Write(
 	outrec *mlrval.Mlrmap,
+	_ *types.Context,
 	bufferedOutputStream *bufio.Writer,
 	outputIsStdout bool,
 ) error {

pkg/terminals/repl/verbs.go

@@ -639,7 +639,8 @@ func writeRecord(repl *Repl, outrec *mlrval.Mlrmap) {
 			outrec.Unflatten(repl.options.WriterOptions.FLATSEP)
 		}
 	}
-	repl.recordWriter.Write(outrec, repl.bufferedRecordOutputStream, true /*outputIsStdout*/)
+	// XXX TEMP
+	repl.recordWriter.Write(outrec, nil, repl.bufferedRecordOutputStream, true /*outputIsStdout*/)
 	repl.bufferedRecordOutputStream.Flush()
 }
 

pkg/types/context.go

@@ -99,6 +99,9 @@ type Context struct {
 	// NF int
 	NR  int64
 	FNR int64
+
+	// XXX 1513
+	JSONHadBrackets bool
 }
 
 // TODO: comment: Remember command-line values to pass along to CST evaluators.

test/cases/dsl-functional-tests/0051/expout

@@ -60,5 +60,3 @@
     "zsgnt": "int"
   }
 ]
-[
-]

test/cases/dsl-output-redirects/0071/expout

@@ -9,5 +9,3 @@ x
 8
 9
 10
-[
-]

test/cases/dsl-sorts/sorta-natural/expout

@@ -2,5 +2,3 @@
 ["X200", "X20", "X2", "X100", "X10", "X1"]
 ["X1", "X2", "X10", "X20", "X100", "X200"]
 ["X200", "X100", "X20", "X10", "X2", "X1"]
-[
-]

test/cases/dsl-sorts/sortmf-within/expout

@@ -18,5 +18,3 @@
   "b": 2,
   "c": 1
 }
-[
-]

test/cases/io-multi/0053/expout

@@ -1,2 +0,0 @@
-[
-]

test/cases/io-multi/0057/expout

@@ -1,2 +0,0 @@
-[
-]