Honor --ors crlf for CSV output (#1810) (#2150)

* Honor --ors CRLF for CSV output (#1810)

The full-CSV record writer validated ORS as newline or
carriage-return/newline, but never propagated the choice to the forked
Go CSV writer's UseCRLF field, so `--ors '\r\n'` (or `--ors crlf`)
silently produced LF line endings. Set UseCRLF from the writer options
so CRLF output is honored. Default behavior (LF) is unchanged, and
other ORS values are still rejected. The CSV-lite and TSV writers
already honored CRLF ORS.

Also: fix a copy-paste "for CSV" in the TSV writer's ORS-validation
message, add unit tests asserting byte-exact line endings (the regtest
harness normalizes CR/LF, so this can't be asserted in test/cases), add
CLI-level regression cases, and update the separators documentation.

This substantially addresses #1722 as well: RFC-4180-style CRLF output
can now be requested on any platform.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Fix errcheck lint: check Flush() error in CSV writer test

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

docs/src/manpage.md

@@ -840,6 +840,9 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        * Default line endings (`--irs` and `--ors`) are newline
          which is interpreted to accept carriage-return/newline files (e.g. on Windows)
          for input, and to produce platform-appropriate line endings on output.
+       * For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+         default) or carriage-return/newline: e.g. `--ors crlf` or `--ors '\r\n'`
+         for RFC-4180-style line endings on any platform.
 
        Notes about all other separators:
 
@@ -4045,5 +4048,5 @@ This is simply a copy of what you should see on running `man mlr` at a command p
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-07-05                         4mMILLER24m(1)
+                                  2026-07-06                         4mMILLER24m(1)
 </pre>

docs/src/manpage.txt

@@ -819,6 +819,9 @@
        * Default line endings (`--irs` and `--ors`) are newline
          which is interpreted to accept carriage-return/newline files (e.g. on Windows)
          for input, and to produce platform-appropriate line endings on output.
+       * For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+         default) or carriage-return/newline: e.g. `--ors crlf` or `--ors '\r\n'`
+         for RFC-4180-style line endings on any platform.
 
        Notes about all other separators:
 
@@ -4024,4 +4027,4 @@
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-07-05                         4mMILLER24m(1)
+                                  2026-07-06                         4mMILLER24m(1)

docs/src/reference-main-flag-list.md

@@ -451,6 +451,9 @@ Notes about line endings:
 * Default line endings (`--irs` and `--ors`) are newline
   which is interpreted to accept carriage-return/newline files (e.g. on Windows)
   for input, and to produce platform-appropriate line endings on output.
+* For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+  default) or carriage-return/newline: e.g. `--ors crlf` or `--ors '\r\n'`
+  for RFC-4180-style line endings on any platform.
 
 Notes about all other separators:
 

docs/src/reference-main-separators.md

@@ -261,8 +261,8 @@ a:4;b:5;c:6;d:>>>,|||;<<<
 
 Notes:
 
-* CSV IRS and ORS must be newline, and CSV IFS must be a single character. (CSV-lite does not have these restrictions.)
-* TSV IRS and ORS must be newline, and TSV IFS must be a tab. (TSV-lite does not have these restrictions.)
+* CSV IRS must be newline -- CR/LF line endings are accepted on input. CSV ORS must be either newline (the default) or carriage-return/newline -- e.g. `--ors crlf` or `--ors '\r\n'` for RFC-4180-style line endings on any platform. CSV IFS must be a single character. (CSV-lite does not have these restrictions.)
+* TSV IRS must be newline -- CR/LF line endings are accepted on input. TSV ORS must be either newline (the default) or carriage-return/newline. TSV IFS must be a tab. (TSV-lite does not have these restrictions.)
 * See the [CSV section](file-formats.md#csvtsvasvusvetc) for information about ASV and USV.
 * JSON and YAML: ignore separator flags from the command line.
 * Headerless CSV overlaps quite a bit with NIDX format using comma for IFS. See also the page on [CSV with and without headers](csv-with-and-without-headers.md).
@@ -270,8 +270,8 @@ Notes:
 
 |            | **RS**  | **FS**  | **PS**   |
 |------------|---------|---------|----------|
-| [**CSV**](file-formats.md#csvtsvasvusvetc)    | Always `\n`; not alterable * | Default `,`; must be single-character    | None     |
-| [**TSV**](file-formats.md#csvtsvasvusvetc)    | Always `\n`; not alterable * |  Default `\t`; must be single-character   | None     |
+| [**CSV**](file-formats.md#csvtsvasvusvetc)    | Default `\n`; may be set to `\r\n` * | Default `,`; must be single-character    | None     |
+| [**TSV**](file-formats.md#csvtsvasvusvetc)    | Default `\n`; may be set to `\r\n` * |  Default `\t`; must be single-character   | None     |
 | [**CSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *   | Default `,`    | None     |
 | [**TSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *  |  Default `\t`   | None     |
 | [**JSON**](file-formats.md#json)   | N/A; records are between `{` and `}` | Always `,`; not alterable    | Always `:`; not alterable |

docs/src/reference-main-separators.md.in

@@ -151,8 +151,8 @@ GENMD-EOF
 
 Notes:
 
-* CSV IRS and ORS must be newline, and CSV IFS must be a single character. (CSV-lite does not have these restrictions.)
-* TSV IRS and ORS must be newline, and TSV IFS must be a tab. (TSV-lite does not have these restrictions.)
+* CSV IRS must be newline -- CR/LF line endings are accepted on input. CSV ORS must be either newline (the default) or carriage-return/newline -- e.g. `--ors crlf` or `--ors '\r\n'` for RFC-4180-style line endings on any platform. CSV IFS must be a single character. (CSV-lite does not have these restrictions.)
+* TSV IRS must be newline -- CR/LF line endings are accepted on input. TSV ORS must be either newline (the default) or carriage-return/newline. TSV IFS must be a tab. (TSV-lite does not have these restrictions.)
 * See the [CSV section](file-formats.md#csvtsvasvusvetc) for information about ASV and USV.
 * JSON and YAML: ignore separator flags from the command line.
 * Headerless CSV overlaps quite a bit with NIDX format using comma for IFS. See also the page on [CSV with and without headers](csv-with-and-without-headers.md).
@@ -160,8 +160,8 @@ Notes:
 
 |            | **RS**  | **FS**  | **PS**   |
 |------------|---------|---------|----------|
-| [**CSV**](file-formats.md#csvtsvasvusvetc)    | Always `\n`; not alterable * | Default `,`; must be single-character    | None     |
-| [**TSV**](file-formats.md#csvtsvasvusvetc)    | Always `\n`; not alterable * |  Default `\t`; must be single-character   | None     |
+| [**CSV**](file-formats.md#csvtsvasvusvetc)    | Default `\n`; may be set to `\r\n` * | Default `,`; must be single-character    | None     |
+| [**TSV**](file-formats.md#csvtsvasvusvetc)    | Default `\n`; may be set to `\r\n` * |  Default `\t`; must be single-character   | None     |
 | [**CSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *   | Default `,`    | None     |
 | [**TSV-lite**](file-formats.md#csvtsvasvusvetc)    | Default `\n` *  |  Default `\t`   | None     |
 | [**JSON**](file-formats.md#json)   | N/A; records are between `{` and `}` | Always `,`; not alterable    | Always `:`; not alterable |

man/manpage.txt

@@ -819,6 +819,9 @@
        * Default line endings (`--irs` and `--ors`) are newline
          which is interpreted to accept carriage-return/newline files (e.g. on Windows)
          for input, and to produce platform-appropriate line endings on output.
+       * For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+         default) or carriage-return/newline: e.g. `--ors crlf` or `--ors '\r\n'`
+         for RFC-4180-style line endings on any platform.
 
        Notes about all other separators:
 
@@ -4024,4 +4027,4 @@
        MIME Type for Comma-Separated Values (CSV) Files, the Miller docsite
        https://miller.readthedocs.io
 
-                                  2026-07-05                         4mMILLER24m(1)
+                                  2026-07-06                         4mMILLER24m(1)

man/mlr.1

@@ -2,12 +2,12 @@
 .\"     Title: mlr
 .\"    Author: [see the "AUTHOR" section]
 .\" Generator: ./mkman.rb
-.\"      Date: 2026-07-05
+.\"      Date: 2026-07-06
 .\"    Manual: \ \&
 .\"    Source: \ \&
 .\"  Language: English
 .\"
-.TH "MILLER" "1" "2026-07-05" "\ \&" "\ \&"
+.TH "MILLER" "1" "2026-07-06" "\ \&" "\ \&"
 .\" -----------------------------------------------------------------
 .\" * Portability definitions
 .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -987,6 +987,9 @@ Notes about line endings:
 * Default line endings (`--irs` and `--ors`) are newline
   which is interpreted to accept carriage-return/newline files (e.g. on Windows)
   for input, and to produce platform-appropriate line endings on output.
+* For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+  default) or carriage-return/newline: e.g. `--ors crlf` or `--ors '\er\en'`
+  for RFC-4180-style line endings on any platform.
 
 Notes about all other separators:
 

pkg/cli/option_parse.go

@@ -158,6 +158,9 @@ Notes about line endings:
 * Default line endings (` + "`--irs`" + ` and ` + "`--ors`" + `) are newline
   which is interpreted to accept carriage-return/newline files (e.g. on Windows)
   for input, and to produce platform-appropriate line endings on output.
+* For CSV, CSV-lite, TSV, and TSV-lite output, ORS may be either newline (the
+  default) or carriage-return/newline: e.g. ` + "`--ors crlf`" + ` or ` + "`--ors '\\r\\n'`" + `
+  for RFC-4180-style line endings on any platform.
 
 Notes about all other separators:
 

pkg/output/record_writer_csv.go

@@ -32,7 +32,7 @@ func NewRecordWriterCSV(writerOptions *cli.TWriterOptions) (*RecordWriterCSV, er
 		return nil, fmt.Errorf("for CSV, OFS can only be a single character")
 	}
 	if writerOptions.ORS != "\n" && writerOptions.ORS != "\r\n" {
-		return nil, fmt.Errorf("for CSV, ORS cannot be altered")
+		return nil, fmt.Errorf("for CSV, ORS must be newline or carriage-return/newline")
 	}
 	writer := &RecordWriterCSV{
 		writerOptions:     writerOptions,
@@ -59,6 +59,9 @@ func (writer *RecordWriterCSV) Write(
 	if writer.csvWriter == nil {
 		writer.csvWriter = csv.NewWriter(bufferedOutputStream)
 		writer.csvWriter.Comma = rune(writer.writerOptions.OFS[0]) // xxx temp -- needs length-1 OFS
+		// Issues #1810 and #1722: honor `--ors '\r\n'` (or `--ors crlf`) for
+		// CSV output. The default remains "\n".
+		writer.csvWriter.UseCRLF = writer.writerOptions.ORS == "\r\n"
 	}
 
 	if writer.firstRecordKeys == nil {

pkg/output/record_writer_csv_test.go

@@ -0,0 +1,99 @@
+// Tests for https://github.com/johnkerl/miller/issues/1810 and
+// https://github.com/johnkerl/miller/issues/1722: `--ors '\r\n'` (or `--ors
+// crlf`) should be honored for CSV/CSV-lite/TSV output. These are unit tests
+// rather than regression-test cases since the regression-test harness
+// normalizes CR/LF to LF before comparing outputs, and so cannot assert
+// byte-exact line endings.
+
+package output
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+
+	"github.com/johnkerl/miller/v6/pkg/cli"
+	"github.com/johnkerl/miller/v6/pkg/mlrval"
+)
+
+func makeTestRecord() *mlrval.Mlrmap {
+	record := mlrval.NewMlrmap()
+	record.PutReference("a", mlrval.FromString("1"))
+	record.PutReference("b", mlrval.FromString("2"))
+	return record
+}
+
+// runWriter drives a record-writer with a single a=1,b=2 record and returns
+// the output bytes.
+func runWriter(t *testing.T, writer IRecordWriter) string {
+	t.Helper()
+	var buffer bytes.Buffer
+	bufferedOutputStream := bufio.NewWriter(&buffer)
+	err := writer.Write(makeTestRecord(), nil, bufferedOutputStream, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = writer.Write(nil, nil, bufferedOutputStream, false) // end of stream
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := bufferedOutputStream.Flush(); err != nil {
+		t.Fatal(err)
+	}
+	return buffer.String()
+}
+
+func TestCSVWriterLFDefault(t *testing.T) {
+	writer, err := NewRecordWriterCSV(&cli.TWriterOptions{OFS: ",", ORS: "\n"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := runWriter(t, writer)
+	expected := "a,b\n1,2\n"
+	if output != expected {
+		t.Fatalf("expected %q, got %q", expected, output)
+	}
+}
+
+func TestCSVWriterCRLF(t *testing.T) {
+	writer, err := NewRecordWriterCSV(&cli.TWriterOptions{OFS: ",", ORS: "\r\n"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := runWriter(t, writer)
+	expected := "a,b\r\n1,2\r\n"
+	if output != expected {
+		t.Fatalf("expected %q, got %q", expected, output)
+	}
+}
+
+func TestCSVWriterRejectsOtherORS(t *testing.T) {
+	_, err := NewRecordWriterCSV(&cli.TWriterOptions{OFS: ",", ORS: ";"})
+	if err == nil {
+		t.Fatal("expected error for ORS \";\" but got none")
+	}
+}
+
+func TestCSVLiteWriterCRLF(t *testing.T) {
+	writer, err := NewRecordWriterCSVLite(&cli.TWriterOptions{OFS: ",", ORS: "\r\n"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := runWriter(t, writer)
+	expected := "a,b\r\n1,2\r\n"
+	if output != expected {
+		t.Fatalf("expected %q, got %q", expected, output)
+	}
+}
+
+func TestTSVWriterCRLF(t *testing.T) {
+	writer, err := NewRecordWriterTSV(&cli.TWriterOptions{OFS: "\t", ORS: "\r\n"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	output := runWriter(t, writer)
+	expected := "a\tb\r\n1\t2\r\n"
+	if output != expected {
+		t.Fatalf("expected %q, got %q", expected, output)
+	}
+}

pkg/output/record_writer_tsv.go

@@ -24,7 +24,7 @@ func NewRecordWriterTSV(writerOptions *cli.TWriterOptions) (*RecordWriterTSV, er
 		return nil, fmt.Errorf("for TSV, OFS cannot be altered")
 	}
 	if writerOptions.ORS != "\n" && writerOptions.ORS != "\r\n" {
-		return nil, fmt.Errorf("for CSV, ORS cannot be altered")
+		return nil, fmt.Errorf("for TSV, ORS must be newline or carriage-return/newline")
 	}
 	return &RecordWriterTSV{
 		writerOptions:     writerOptions,

test/cases/io-csv-ors-crlf/0001/cmd

@@ -0,0 +1 @@
+mlr --icsv --ocsv --ors crlf cat test/input/line-term-lf.csv

test/cases/io-csv-ors-crlf/0001/expout

@@ -0,0 +1,11 @@
+a,b,i,x,y
+pan,pan,1,0.34679014,0.72680286
+eks,pan,2,0.75867996,0.52215111
+wye,wye,3,0.20460331,0.33831853
+eks,wye,4,0.38139939,0.13418874
+wye,pan,5,0.57328892,0.86362447
+zee,pan,6,0.52712616,0.49322129
+eks,zee,7,0.61178406,0.18788492
+zee,wye,8,0.59855401,0.97618139
+hat,wye,9,0.03144188,0.74955076
+pan,wye,10,0.50262601,0.95261836

test/cases/io-csv-ors-crlf/0002/cmd

@@ -0,0 +1 @@
+mlr --icsv --ocsv --ors crlf cat test/input/line-term-crlf.csv

test/cases/io-csv-ors-crlf/0002/expout

@@ -0,0 +1,11 @@
+a,b,i,x,y
+pan,pan,1,0.34679014,0.72680286
+eks,pan,2,0.75867996,0.52215111
+wye,wye,3,0.20460331,0.33831853
+eks,wye,4,0.38139939,0.13418874
+wye,pan,5,0.57328892,0.86362447
+zee,pan,6,0.52712616,0.49322129
+eks,zee,7,0.61178406,0.18788492
+zee,wye,8,0.59855401,0.97618139
+hat,wye,9,0.03144188,0.74955076
+pan,wye,10,0.50262601,0.95261836

test/cases/io-csv-ors-crlf/0003/cmd

@@ -0,0 +1 @@
+mlr --icsv --ocsv --ors lf cat test/input/line-term-crlf.csv

test/cases/io-csv-ors-crlf/0003/expout

@@ -0,0 +1,11 @@
+a,b,i,x,y
+pan,pan,1,0.34679014,0.72680286
+eks,pan,2,0.75867996,0.52215111
+wye,wye,3,0.20460331,0.33831853
+eks,wye,4,0.38139939,0.13418874
+wye,pan,5,0.57328892,0.86362447
+zee,pan,6,0.52712616,0.49322129
+eks,zee,7,0.61178406,0.18788492
+zee,wye,8,0.59855401,0.97618139
+hat,wye,9,0.03144188,0.74955076
+pan,wye,10,0.50262601,0.95261836

test/cases/io-csv-ors-crlf/0004/cmd

@@ -0,0 +1 @@
+mlr --icsv --otsv --ors crlf cat test/input/line-term-lf.csv

test/cases/io-csv-ors-crlf/0004/expout

@@ -0,0 +1,11 @@
+a	b	i	x	y
+pan	pan	1	0.34679014	0.72680286
+eks	pan	2	0.75867996	0.52215111
+wye	wye	3	0.20460331	0.33831853
+eks	wye	4	0.38139939	0.13418874
+wye	pan	5	0.57328892	0.86362447
+zee	pan	6	0.52712616	0.49322129
+eks	zee	7	0.61178406	0.18788492
+zee	wye	8	0.59855401	0.97618139
+hat	wye	9	0.03144188	0.74955076
+pan	wye	10	0.50262601	0.95261836

test/cases/io-csv-ors-crlf/0005/cmd

@@ -0,0 +1 @@
+mlr --icsv --ocsv --ors semicolon cat test/input/line-term-lf.csv

test/cases/io-csv-ors-crlf/0005/experr

@@ -0,0 +1 @@
+mlr: for CSV, ORS must be newline or carriage-return/newline