tomljson: port to v2 (#725)

README.md

@@ -207,6 +207,17 @@ In case of trouble: [Go Modules FAQ][mod-faq].
 
 [mod-faq]: https://github.com/golang/go/wiki/Modules#why-does-installing-a-tool-via-go-get-fail-with-error-cannot-find-main-module
 
+## Tools
+
+Go-toml provides one handy command line tool:
+
+ * `tomljson`: Reads a TOML file and outputs its JSON representation.
+
+    ```
+    $ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
+    $ tomljson --help
+    ```
+
 ## Migrating from v1
 
 This section describes the differences between v1 and v2, with some pointers on

cmd/tomljson/main.go

@@ -0,0 +1,79 @@
+// Tomljson reads TOML and converts to JSON.
+//
+// Usage:
+//   cat file.toml | tomljson > file.json
+//   tomljson file1.toml > file.json
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+func usage() {
+	fmt.Fprint(os.Stderr, `tomljson can be used in two ways:
+Reading from stdin:
+  cat file.toml | tomljson > file.json
+
+Reading from a file:
+  tomljson file.toml > file.json
+`)
+}
+
+func init() {
+	flag.Usage = usage
+}
+
+func main() {
+	flag.Parse()
+	os.Exit(processMain(flag.Args(), os.Stdin, os.Stdout, os.Stderr))
+}
+
+func processMain(files []string, input io.Reader, output, error io.Writer) int {
+	err := run(files, input, output)
+	if err != nil {
+		var derr *toml.DecodeError
+		if errors.As(err, &derr) {
+			fmt.Fprintln(error, derr.String())
+			row, col := derr.Position()
+			fmt.Fprintln(error, "error occurred at row", row, "column", col)
+		} else {
+			fmt.Fprintln(error, err.Error())
+		}
+		return -1
+	}
+	return 0
+}
+
+func run(files []string, input io.Reader, output io.Writer) error {
+	if len(files) > 0 {
+		f, err := os.Open(files[0])
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		input = f
+	}
+
+	return convert(input, output)
+}
+
+func convert(r io.Reader, w io.Writer) error {
+	var v interface{}
+
+	d := toml.NewDecoder(r)
+	err := d.Decode(&v)
+	if err != nil {
+		return err
+	}
+
+	e := json.NewEncoder(w)
+	e.SetIndent("", "  ")
+	return e.Encode(v)
+}

cmd/tomljson/main_test.go

@@ -0,0 +1,154 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func expectBufferEquality(t *testing.T, name string, buffer *bytes.Buffer, expected string) {
+	t.Helper()
+	output := buffer.String()
+	assert.Equal(t, expected, output, fmt.Sprintf("%s does not match", name))
+}
+
+func expectProcessMainResults(t *testing.T, input io.Reader, args []string, exitCode int, expectedOutput string, expectedError string) {
+	t.Helper()
+	outputBuffer := new(bytes.Buffer)
+	errorBuffer := new(bytes.Buffer)
+
+	returnCode := processMain(args, input, outputBuffer, errorBuffer)
+
+	expectBufferEquality(t, "stdout", outputBuffer, expectedOutput)
+	expectBufferEquality(t, "stderr", errorBuffer, expectedError)
+
+	require.Equal(t, exitCode, returnCode, "exit codes should match")
+}
+
+func expect(t *testing.T, input string, args []string, exitCode int, expectedOutput string, expectedError string) {
+	t.Helper()
+	r := strings.NewReader(input)
+	expectProcessMainResults(t, r, args, exitCode, expectedOutput, expectedError)
+}
+
+func TestProcessMainReadFromStdin(t *testing.T) {
+	input := `
+		[mytoml]
+		a = 42`
+	expectedOutput := `{
+  "mytoml": {
+    "a": 42
+  }
+}
+`
+	expect(t, input, []string{}, 0, expectedOutput, ``)
+}
+
+func TestProcessMainReadInvalidTOML(t *testing.T) {
+	input := `bad = []]`
+	expectedError := `1| bad = []]
+ |         ~ expected newline but got U+005D ']'
+error occurred at row 1 column 9
+`
+
+	expect(t, input, []string{}, -1, ``, expectedError)
+}
+
+type badReader struct{}
+
+func (r *badReader) Read([]byte) (int, error) {
+	return 0, fmt.Errorf("reader failed on purpose")
+}
+
+func TestProcessMainProblemReadingFile(t *testing.T) {
+	expectedError := `toml: reader failed on purpose
+`
+	input := &badReader{}
+
+	expectProcessMainResults(t, input, []string{}, -1, ``, expectedError)
+}
+
+func TestProcessMainReadFromFile(t *testing.T) {
+	input := `
+		[mytoml]
+		a = 42`
+
+	tmpfile, err := ioutil.TempFile("", "example.toml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := tmpfile.Write([]byte(input)); err != nil {
+		t.Fatal(err)
+	}
+
+	defer os.Remove(tmpfile.Name())
+
+	expectedOutput := `{
+  "mytoml": {
+    "a": 42
+  }
+}
+`
+	expectedError := ``
+	expectedExitCode := 0
+
+	expect(t, ``, []string{tmpfile.Name()}, expectedExitCode, expectedOutput, expectedError)
+}
+
+func TestProcessMainReadFromMissingFile(t *testing.T) {
+	var expectedError string
+	if runtime.GOOS == "windows" {
+		expectedError = `open /this/file/does/not/exist: The system cannot find the path specified.
+`
+	} else {
+		expectedError = `open /this/file/does/not/exist: no such file or directory
+`
+	}
+
+	expect(t, ``, []string{"/this/file/does/not/exist"}, -1, ``, expectedError)
+}
+
+func TestMainUsage(t *testing.T) {
+	out := doAndCaptureStderr(usage)
+	require.NotEmpty(t, out)
+}
+
+func doAndCaptureStderr(f func()) string {
+	orig := os.Stderr
+	defer func() { os.Stderr = orig }()
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		panic(err)
+	}
+
+	b := new(bytes.Buffer)
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, err := io.Copy(b, r)
+		if err != nil {
+			panic(err)
+		}
+	}()
+
+	os.Stderr = w
+
+	f()
+
+	w.Close()
+	wg.Wait()
+
+	return b.String()
+}