Render to Writer instead of string (#39)

The Render function has been changed to take a `Writer` instead of returning a string. This makes it possible to generate documents without having the whole content in memory.

This also removes the `gomponents.Write` function, which is now redundant.

Furthermore, the `el.Document` function has been changed to only take one child, as multiple children never make sense for it. (It's not even a child, more a sibling.)

1 files changed, 44 insertions, 37 deletions

diff --git a/gomponents_test.go b/gomponents_test.go
index 2efdd7a..3028723 100644
--- a/gomponents_test.go
+++ b/gomponents_test.go
@@ -3,6 +3,7 @@ package gomponents_test
 import (
 	"errors"
 	"fmt"
+	"io"
 	"strings"
 	"testing"
 
@@ -12,7 +13,10 @@ import (
 
 func TestNodeFunc(t *testing.T) {
 	t.Run("implements fmt.Stringer", func(t *testing.T) {
-		fn := g.NodeFunc(func() string { return "hat" })
+		fn := g.NodeFunc(func(w io.Writer) error {
+			_, _ = w.Write([]byte("hat"))
+			return nil
+		})
 		if fn.String() != "hat" {
 			t.FailNow()
 		}
@@ -56,24 +60,29 @@ func BenchmarkAttr(b *testing.B) {
 	b.Run("boolean attributes", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			a := g.Attr("hat")
-			a.Render()
+			_ = a.Render(&strings.Builder{})
 		}
 	})
 
 	b.Run("name-value attributes", func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			a := g.Attr("hat", "party")
-			a.Render()
+			_ = a.Render(&strings.Builder{})
 		}
 	})
 }
 
 type outsider struct{}
 
-func (o outsider) Render() string {
+func (o outsider) String() string {
 	return "outsider"
 }
 
+func (o outsider) Render(w io.Writer) error {
+	_, _ = w.Write([]byte("outsider"))
+	return nil
+}
+
 func TestEl(t *testing.T) {
 	t.Run("renders an empty element if no children given", func(t *testing.T) {
 		e := g.El("div")
@@ -101,9 +110,21 @@ func TestEl(t *testing.T) {
 	})
 
 	t.Run("does not fail on nil node", func(t *testing.T) {
-		e := g.El("div", g.El("span"), nil, g.El("span"))
+		e := g.El("div", nil, g.El("span"), nil, g.El("span"))
 		assert.Equal(t, `<div><span /><span /></div>`, e)
 	})
+
+	t.Run("returns render error on cannot write", func(t *testing.T) {
+		e := g.El("div")
+		err := e.Render(&erroringWriter{})
+		assert.Error(t, err)
+	})
+}
+
+type erroringWriter struct{}
+
+func (w *erroringWriter) Write(p []byte) (n int, err error) {
+	return 0, errors.New("no thanks")
 }
 
 func TestText(t *testing.T) {
@@ -127,34 +148,6 @@ func TestRaw(t *testing.T) {
 	})
 }
 
-type erroringWriter struct{}
-
-func (w *erroringWriter) Write(p []byte) (n int, err error) {
-	return 0, errors.New("don't want to write")
-}
-
-func TestWrite(t *testing.T) {
-	t.Run("writes to the writer", func(t *testing.T) {
-		e := g.El("div")
-		var b strings.Builder
-		err := g.Write(&b, e)
-		if err != nil {
-			t.FailNow()
-		}
-		if b.String() != e.Render() {
-			t.FailNow()
-		}
-	})
-
-	t.Run("errors on write error", func(t *testing.T) {
-		e := g.El("div")
-		err := g.Write(&erroringWriter{}, e)
-		if err == nil {
-			t.FailNow()
-		}
-	})
-}
-
 func TestGroup(t *testing.T) {
 	t.Run("groups multiple nodes into one", func(t *testing.T) {
 		children := []g.Node{g.El("div", g.Attr("id", "hat")), g.El("div")}
@@ -164,14 +157,28 @@ func TestGroup(t *testing.T) {
 
 	t.Run("panics on direct render", func(t *testing.T) {
 		e := g.Group(nil)
-		panicced := false
+		panicked := false
+		defer func() {
+			if err := recover(); err != nil {
+				panicked = true
+			}
+		}()
+		_ = e.Render(nil)
+		if !panicked {
+			t.FailNow()
+		}
+	})
+
+	t.Run("panics on direct string", func(t *testing.T) {
+		e := g.Group(nil).(fmt.Stringer)
+		panicked := false
 		defer func() {
 			if err := recover(); err != nil {
-				panicced = true
+				panicked = true
 			}
 		}()
-		e.Render()
-		if !panicced {
+		_ = e.String()
+		if !panicked {
 			t.FailNow()
 		}
 	})