Added WriteToTempFile function

Author: cmaglie

go.mod

@@ -2,4 +2,7 @@ module github.com/arduino/go-paths-helper
 
 go 1.12
 
-require github.com/stretchr/testify v1.3.0
+require (
+	github.com/pkg/errors v0.9.1
+	github.com/stretchr/testify v1.3.0
+)

go.sum

@@ -1,5 +1,7 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

paths.go

@@ -37,6 +37,8 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	"github.com/pkg/errors"
 )
 
 // Path represents a path
@@ -457,6 +459,23 @@ func (p *Path) WriteFile(data []byte) error {
 	return ioutil.WriteFile(p.path, data, os.FileMode(0644))
 }
 
+// WriteToTempFile writes data to a newly generated temporary file.
+// dir and prefix have the same meaning for MkTempFile.
+// In case of success the Path to the temp file is returned.
+func WriteToTempFile(data []byte, dir *Path, prefix string) (res *Path, err error) {
+	f, err := MkTempFile(dir, prefix)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	if n, err := f.Write(data); err != nil {
+		return nil, err
+	} else if n < len(data) {
+		return nil, errors.Errorf("could not write all data (written %d bytes out of %d)", n, len(data))
+	}
+	return New(f.Name()), nil
+}
+
 // ReadFileAsLines reads the file named by filename and returns it as an
 // array of lines. This function takes care of the newline encoding
 // differences between different OS

paths_test.go

@@ -31,6 +31,7 @@ package paths
 
 import (
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -337,3 +338,18 @@ func TestRelativeTo(t *testing.T) {
 	require.Error(t, err)
 	require.Nil(t, res)
 }
+
+func TestWriteToTempFile(t *testing.T) {
+	tmpDir := New("_testdata", "tmp")
+	tmpData := []byte("test")
+	tmp, err := WriteToTempFile(tmpData, tmpDir, "prefix")
+	defer tmp.Remove()
+	require.NoError(t, err)
+	require.True(t, strings.HasPrefix(tmp.Base(), "prefix"))
+	inside, err := tmp.IsInsideDir(tmpDir)
+	require.NoError(t, err)
+	require.True(t, inside)
+	data, err := tmp.ReadFile()
+	require.NoError(t, err)
+	require.Equal(t, tmpData, data)
+}