Add CSV support to transform.Unmarshal

Fixes #5555

4 files changed, 75 insertions, 12 deletions

diff --git a/parser/metadecoders/decoder.go b/parser/metadecoders/decoder.go
index 6da791c73..0ca8575fe 100644
--- a/parser/metadecoders/decoder.go
+++ b/parser/metadecoders/decoder.go
@@ -14,6 +14,8 @@
 package metadecoders
 
 import (
+	"bytes"
+	"encoding/csv"
 	"encoding/json"
 	"fmt"
 
@@ -27,22 +29,37 @@ import (
 	yaml "gopkg.in/yaml.v2"
 )
 
+// Decoder provides some configuration options for the decoders.
+type Decoder struct {
+	// Comma is the field delimiter used in the CSV decoder. It defaults to ','.
+	Comma rune
+
+	// Comment, if not 0, is the comment character ued in the CSV decoder. Lines beginning with the
+	// Comment character without preceding whitespace are ignored.
+	Comment rune
+}
+
+// Default is a Decoder in its default configuration.
+var Default = Decoder{
+	Comma: ',',
+}
+
 // UnmarshalToMap will unmarshall data in format f into a new map. This is
 // what's needed for Hugo's front matter decoding.
-func UnmarshalToMap(data []byte, f Format) (map[string]interface{}, error) {
+func (d Decoder) UnmarshalToMap(data []byte, f Format) (map[string]interface{}, error) {
 	m := make(map[string]interface{})
 	if data == nil {
 		return m, nil
 	}
 
-	err := unmarshal(data, f, &m)
+	err := d.unmarshal(data, f, &m)
 
 	return m, err
 }
 
 // UnmarshalFileToMap is the same as UnmarshalToMap, but reads the data from
 // the given filename.
-func UnmarshalFileToMap(fs afero.Fs, filename string) (map[string]interface{}, error) {
+func (d Decoder) UnmarshalFileToMap(fs afero.Fs, filename string) (map[string]interface{}, error) {
 	format := FormatFromString(filename)
 	if format == "" {
 		return nil, errors.Errorf("%q is not a valid configuration format", filename)
@@ -52,23 +69,29 @@ func UnmarshalFileToMap(fs afero.Fs, filename string) (map[string]interface{}, e
 	if err != nil {
 		return nil, err
 	}
-	return UnmarshalToMap(data, format)
+	return d.UnmarshalToMap(data, format)
 }
 
 // Unmarshal will unmarshall data in format f into an interface{}.
 // This is what's needed for Hugo's /data handling.
-func Unmarshal(data []byte, f Format) (interface{}, error) {
+func (d Decoder) Unmarshal(data []byte, f Format) (interface{}, error) {
 	if data == nil {
-		return make(map[string]interface{}), nil
+		switch f {
+		case CSV:
+			return make([][]string, 0), nil
+		default:
+			return make(map[string]interface{}), nil
+		}
+
 	}
 	var v interface{}
-	err := unmarshal(data, f, &v)
+	err := d.unmarshal(data, f, &v)
 
 	return v, err
 }
 
 // unmarshal unmarshals data in format f into v.
-func unmarshal(data []byte, f Format, v interface{}) error {
+func (d Decoder) unmarshal(data []byte, f Format, v interface{}) error {
 
 	var err error
 
@@ -116,6 +139,9 @@ func unmarshal(data []byte, f Format, v interface{}) error {
 				*v.(*interface{}) = mm
 			}
 		}
+	case CSV:
+		return d.unmarshalCSV(data, v)
+
 	default:
 		return errors.Errorf("unmarshal of format %q is not supported", f)
 	}
@@ -128,6 +154,28 @@ func unmarshal(data []byte, f Format, v interface{}) error {
 
 }
 
+func (d Decoder) unmarshalCSV(data []byte, v interface{}) error {
+	r := csv.NewReader(bytes.NewReader(data))
+	r.Comma = d.Comma
+	r.Comment = d.Comment
+
+	records, err := r.ReadAll()
+	if err != nil {
+		return err
+	}
+
+	switch v.(type) {
+	case *interface{}:
+		*v.(*interface{}) = records
+	default:
+		return errors.Errorf("CSV cannot be unmarshaled into %T", v)
+
+	}
+
+	return nil
+
+}
+
 func toFileError(f Format, err error) error {
 	return herrors.ToFileError(string(f), err)
 }
diff --git a/parser/metadecoders/decoder_test.go b/parser/metadecoders/decoder_test.go
index 94cfd5a9a..38d002dd8 100644
--- a/parser/metadecoders/decoder_test.go
+++ b/parser/metadecoders/decoder_test.go
@@ -26,6 +26,8 @@ func TestUnmarshalToMap(t *testing.T) {
 
 	expect := map[string]interface{}{"a": "b"}
 
+	d := Default
+
 	for i, test := range []struct {
 		data   string
 		format Format
@@ -40,9 +42,10 @@ func TestUnmarshalToMap(t *testing.T) {
 		{`#+a: b`, ORG, expect},
 		// errors
 		{`a = b`, TOML, false},
+		{`a,b,c`, CSV, false}, // Use Unmarshal for CSV
 	} {
 		msg := fmt.Sprintf("%d: %s", i, test.format)
-		m, err := UnmarshalToMap([]byte(test.data), test.format)
+		m, err := d.UnmarshalToMap([]byte(test.data), test.format)
 		if b, ok := test.expect.(bool); ok && !b {
 			assert.Error(err, msg)
 		} else {
@@ -57,6 +60,8 @@ func TestUnmarshalToInterface(t *testing.T) {
 
 	expect := map[string]interface{}{"a": "b"}
 
+	d := Default
+
 	for i, test := range []struct {
 		data   string
 		format Format
@@ -67,12 +72,13 @@ func TestUnmarshalToInterface(t *testing.T) {
 		{`#+a: b`, ORG, expect},
 		{`a = "b"`, TOML, expect},
 		{`a: "b"`, YAML, expect},
+		{`a,b,c`, CSV, [][]string{[]string{"a", "b", "c"}}},
 		{"a: Easy!\nb:\n  c: 2\n  d: [3, 4]", YAML, map[string]interface{}{"a": "Easy!", "b": map[string]interface{}{"c": 2, "d": []interface{}{3, 4}}}},
 		// errors
 		{`a = "`, TOML, false},
 	} {
 		msg := fmt.Sprintf("%d: %s", i, test.format)
-		m, err := Unmarshal([]byte(test.data), test.format)
+		m, err := d.Unmarshal([]byte(test.data), test.format)
 		if b, ok := test.expect.(bool); ok && !b {
 			assert.Error(err, msg)
 		} else {
diff --git a/parser/metadecoders/format.go b/parser/metadecoders/format.go
index 4a30898fe..719fbf100 100644
--- a/parser/metadecoders/format.go
+++ b/parser/metadecoders/format.go
@@ -31,6 +31,7 @@ const (
 	JSON Format = "json"
 	TOML Format = "toml"
 	YAML Format = "yaml"
+	CSV  Format = "csv"
 )
 
 // FormatFromString turns formatStr, typically a file extension without any ".",
@@ -51,6 +52,8 @@ func FormatFromString(formatStr string) Format {
 		return TOML
 	case "org":
 		return ORG
+	case "csv":
+		return CSV
 	}
 
 	return ""
@@ -88,11 +91,16 @@ func FormatFromFrontMatterType(typ pageparser.ItemType) Format {
 // FormatFromContentString tries to detect the format (JSON, YAML or TOML)
 // in the given string.
 // It return an empty string if no format could be detected.
-func FormatFromContentString(data string) Format {
+func (d Decoder) FormatFromContentString(data string) Format {
+	csvIdx := strings.IndexRune(data, d.Comma)
 	jsonIdx := strings.Index(data, "{")
 	yamlIdx := strings.Index(data, ":")
 	tomlIdx := strings.Index(data, "=")
 
+	if isLowerIndexThan(csvIdx, jsonIdx, yamlIdx, tomlIdx) {
+		return CSV
+	}
+
 	if isLowerIndexThan(jsonIdx, yamlIdx, tomlIdx) {
 		return JSON
 	}
diff --git a/parser/metadecoders/format_test.go b/parser/metadecoders/format_test.go
index 6243b3f1e..7794843b1 100644
--- a/parser/metadecoders/format_test.go
+++ b/parser/metadecoders/format_test.go
@@ -88,12 +88,13 @@ func TestFormatFromContentString(t *testing.T) {
 		{`foo: "bar"`, YAML},
 		{`foo:"bar"`, YAML},
 		{`{ "foo": "bar"`, JSON},
+		{`a,b,c"`, CSV},
 		{`asdfasdf`, Format("")},
 		{``, Format("")},
 	} {
 		errMsg := fmt.Sprintf("[%d] %s", i, test.data)
 
-		result := FormatFromContentString(test.data)
+		result := Default.FormatFromContentString(test.data)
 
 		assert.Equal(test.expect, result, errMsg)
 	}