Added tabbing help with some tests.

struct.go

@@ -71,6 +71,7 @@ type CustomTypescript interface {
 }
 
 func (s *Struct) RenderCustom(opts *Options, w io.Writer) (err error) {
+	ww := newTabScanner(w, opts.indents[1])
 	ctit := reflect.TypeOf((*CustomTypescript)(nil)).Elem()
 	var implementingType reflect.Type = nil
 	if s.t.Implements(ctit) {
@@ -84,12 +85,12 @@ func (s *Struct) RenderCustom(opts *Options, w io.Writer) (err error) {
 		if !ok {
 			return errors.New("couldn't get method RenderCustomTypescript")
 		}
-		_, err = fmt.Fprintf(w, "\n")
+		_, err = fmt.Fprintf(ww, "\n")
 		o := reflect.New(s.t)
 		if implementingType.Kind() != reflect.Ptr {
 			o = o.Elem()
 		}
-		wv := reflect.ValueOf(w)
+		wv := reflect.ValueOf(ww)
 		r := m.Func.Call([]reflect.Value{o, wv})
 		if len(r) > 0 && !r[0].IsNil() {
 			switch r0t := r[0].Interface().(type) {

tabscanner.go

@@ -0,0 +1,37 @@
+package struct2ts
+
+import "io"
+
+type tabScanner struct {
+	output io.Writer
+	tabs   []byte
+}
+
+func (ts *tabScanner) Write(bs []byte) (n int, err error) {
+	p := 0
+	var rn int
+	for pos, b := range bs {
+		switch b {
+		case '\n':
+			rn, err = ts.output.Write(bs[p : pos+1])
+			n += rn
+			if err != nil {
+				return
+			}
+			_, err = ts.output.Write(ts.tabs)
+			if err != nil {
+				return
+			}
+			p = pos + 1
+		}
+	}
+	rn, err = ts.output.Write(bs[p:])
+	return n + rn, err
+}
+
+func newTabScanner(w io.Writer, tabs string) io.Writer {
+	return &tabScanner{
+		output: w,
+		tabs:   []byte(tabs),
+	}
+}

tabscanner_test.go

@@ -0,0 +1,95 @@
+package struct2ts
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestTabScanner_Write(t *testing.T) {
+	tests := []struct {
+		Name  string
+		Input struct {
+			Tabs    string
+			Buffers []string
+		}
+		Expected struct {
+			Output string
+			n      *int
+		}
+	}{
+		{
+			"One new line mid string - one input, 3 spaces",
+			struct {
+				Tabs    string
+				Buffers []string
+			}{Tabs: "   ", Buffers: []string{"Hello how are you?\nI'm fine thanks!"}},
+			struct {
+				Output string
+				n      *int
+			}{Output: "Hello how are you?\n   I'm fine thanks!"},
+		},
+		{
+			"One new line end string - one input, 3 spaces",
+			struct {
+				Tabs    string
+				Buffers []string
+			}{Tabs: "   ", Buffers: []string{"Hello how are you?\n"}},
+			struct {
+				Output string
+				n      *int
+			}{Output: "Hello how are you?\n   "},
+		},
+		{
+			"One new line start string - one input, 3 spaces",
+			struct {
+				Tabs    string
+				Buffers []string
+			}{Tabs: "   ", Buffers: []string{"\nHello how are you?"}},
+			struct {
+				Output string
+				n      *int
+			}{Output: "\n   Hello how are you?"},
+		},
+		{
+			"empty string",
+			struct {
+				Tabs    string
+				Buffers []string
+			}{Tabs: "   ", Buffers: []string{""}},
+			struct {
+				Output string
+				n      *int
+			}{Output: ""},
+		},
+		{
+			"Just a new line",
+			struct {
+				Tabs    string
+				Buffers []string
+			}{Tabs: "   ", Buffers: []string{"\n"}},
+			struct {
+				Output string
+				n      *int
+			}{Output: "\n   "},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.Name, func(t *testing.T) {
+			outputBuffer := bytes.NewBuffer(nil)
+			ts := newTabScanner(outputBuffer, test.Input.Tabs)
+			for _, s := range test.Input.Buffers {
+				_, err := ts.Write([]byte(s))
+				if err != nil {
+					t.Error("Buffer write error", err)
+				}
+			}
+			if outputBuffer.String() != test.Expected.Output {
+				t.Log("Output buffer doesn't match. Got ")
+				t.Log(outputBuffer.String())
+				t.Log("expected")
+				t.Log(test.Expected.Output)
+				t.Fail()
+			}
+		})
+	}
+}