add WriteMultiline to save to multiline json format

examples/14-tvtomultilinejson/exampletvtomultilinejson.go

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+
+// Example for: *tagvalue*, *json*
+
+// This example demonstrates loading an SPDX tag-value file from disk into memory,
+// and re-saving it to a different multiline json file on disk.
+// Run project: go run exampletvtomultilinejson.go ../sample-docs/tv/hello.spdx example.json
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spdx/tools-golang/json"
+	"github.com/spdx/tools-golang/tagvalue"
+)
+
+func main() {
+
+	// check that we've received the right number of arguments
+	args := os.Args
+	if len(args) != 3 {
+		fmt.Printf("Usage: %v <spdx-file-in> <json-file-out>\n", args[0])
+		fmt.Printf("  Load SPDX tag-value file <spdx-file-in>, and\n")
+		fmt.Printf("  save it out to multiline JSON <json-file-out>.\n")
+		return
+	}
+
+	// open the SPDX file
+	fileIn := args[1]
+	r, err := os.Open(fileIn)
+	if err != nil {
+		fmt.Printf("Error while opening %v for reading: %v", fileIn, err)
+		return
+	}
+	defer r.Close()
+
+	// try to load the SPDX file's contents as a tag-value file
+	doc, err := tagvalue.Read(r)
+	if err != nil {
+		fmt.Printf("Error while parsing %v: %v", args[1], err)
+		return
+	}
+
+	// if we got here, the file is now loaded into memory.
+	fmt.Printf("Successfully loaded %s\n", args[1])
+
+	// we can now save it back to disk, using jsonsaver.
+
+	// create a new file for writing
+	fileOut := args[2]
+	w, err := os.Create(fileOut)
+	if err != nil {
+		fmt.Printf("Error while opening %v for writing: %v", fileOut, err)
+		return
+	}
+	defer w.Close()
+
+	// try to save the document to disk as multiline JSON file
+	err = json.WriteMultiline(doc, w)
+	if err != nil {
+		fmt.Printf("Error while saving %v: %v", fileOut, err)
+		return
+	}
+
+	// it worked
+	fmt.Printf("Successfully saved %s\n", fileOut)
+}

json/writer.go

@@ -23,3 +23,18 @@ func Write(doc common.AnyDocument, w io.Writer) error {
 
 	return nil
 }
+
+// WriteMultiline takes an SPDX Document and an io.Writer, and writes the document to the writer in JSON format with indents (multiline format).
+func WriteMultiline(doc common.AnyDocument, w io.Writer) error {
+	buf, err := json.MarshalIndent(doc, "", "  ")
+	if err != nil {
+		return err
+	}
+
+	_, err = w.Write(buf)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}

spdx/v2/v2_2/json/json_test.go

@@ -92,6 +92,30 @@ func Test_Write(t *testing.T) {
 	}
 }
 
+func Test_MultilineWrite(t *testing.T) {
+	want := example.Copy()
+
+	w := &bytes.Buffer{}
+
+	if err := json.WriteMultiline(&want, w); err != nil {
+		t.Errorf("Write() error = %v", err.Error())
+		return
+	}
+
+	// we should be able to parse what the writer wrote, and it should be identical to the original struct we wrote
+	var got spdx.Document
+	err := json.ReadInto(bytes.NewReader(w.Bytes()), &got)
+	if err != nil {
+		t.Errorf("failed to parse written document: %v", err.Error())
+		return
+	}
+
+	if !cmp.Equal(want, got, cmpopts.IgnoreUnexported(spdx.Package{})) {
+		t.Errorf("got incorrect struct after writing and re-parsing JSON example: %s", cmp.Diff(want, got, cmpopts.IgnoreUnexported(spdx.Package{})))
+		return
+	}
+}
+
 func Test_ShorthandFields(t *testing.T) {
 	contents := `{
 		"spdxVersion": "SPDX-2.2",

spdx/v2/v2_3/json/json_test.go

@@ -81,6 +81,29 @@ func Test_Write(t *testing.T) {
 		return
 	}
 }
+func Test_MultilineWrite(t *testing.T) {
+	want := example.Copy()
+
+	w := &bytes.Buffer{}
+
+	if err := json.WriteMultiline(&want, w); err != nil {
+		t.Errorf("Write() error = %v", err.Error())
+		return
+	}
+
+	// we should be able to parse what the writer wrote, and it should be identical to the original struct we wrote
+	var got spdx.Document
+	err := json.ReadInto(bytes.NewReader(w.Bytes()), &got)
+	if err != nil {
+		t.Errorf("failed to parse written document: %v", err.Error())
+		return
+	}
+
+	if !cmp.Equal(want, got, cmpopts.IgnoreUnexported(spdx.Package{})) {
+		t.Errorf("got incorrect struct after writing and re-parsing JSON example: %s", cmp.Diff(want, got, cmpopts.IgnoreUnexported(spdx.Package{})))
+		return
+	}
+}
 
 func Test_ShorthandFields(t *testing.T) {
 	contents := `{