fix no-newline edge case

Author: beyang

diff/diff_test.go

@@ -5,7 +5,6 @@ import (
 	"io/ioutil"
 	"path/filepath"
 	"reflect"
-	"strings"
 	"testing"
 )
 
@@ -54,7 +53,11 @@ func TestParseHunksAndPrintHunks(t *testing.T) {
 		{
 			filename: "sample_hunks_no_newline.diff",
 		},
+		{
+			filename: "sample_hunks_no_newline2.diff",
+		},
 		{filename: "empty.diff"},
+		{filename: "oneline_hunk.diff"},
 	}
 	for _, test := range tests {
 		diffData, err := ioutil.ReadFile(filepath.Join("testdata", test.filename))
@@ -80,6 +83,25 @@ func TestParseHunksAndPrintHunks(t *testing.T) {
 	}
 }
 
+func TestStripModifierLines(t *testing.T) {
+	orig := `- a
+\ No newline at end of file
++ b
+\ No newline at end of file
+`
+	want := `- a
++ b
+`
+
+	hunks := []*Hunk{{Body: []byte(orig)}}
+	StripModifierLines(hunks)
+	stripped := string(hunks[0].Body)
+
+	if stripped != want {
+		t.Errorf("Want:\n%s\nbut got:\n%s", want, stripped)
+	}
+}
+
 func TestParseFileDiffAndPrintFileDiff(t *testing.T) {
 	tests := []struct {
 		filename     string
@@ -160,36 +182,6 @@ func TestParseMultiFileDiffAndPrintMultiFileDiff(t *testing.T) {
 	}
 }
 
-func TestNoNewlineAtEnd(t *testing.T) {
-	orig := `@@ -1,1 +1,1 @@
--b
-+b
-\ No newline at end of file
-`
-
-	hunks, err := ParseHunks([]byte(orig))
-	if err != nil {
-		t.Fatal("ParseHunks: %s", err)
-	}
-
-	for _, hunk := range hunks {
-		if body := string(hunk.Body); strings.Contains(body, "No newline") {
-			t.Errorf("after parse, hunk body contains 'No newline...' string\n\nbody is:\n%q", body)
-		}
-		if bytes.HasSuffix(hunk.Body, []byte{'\n'}) {
-			t.Errorf("after parse, hunk body ends with newline\n\nbody is:\n%q", hunk.Body)
-		}
-
-		printed, err := PrintHunks(hunks)
-		if err != nil {
-			t.Fatal("PrintHunks: %s", err)
-		}
-		if printed := string(printed); printed != orig {
-			t.Errorf("printed diff hunks != original diff hunks\n\n# PrintHunks output:\n%q\n\n# Original:\n%q", printed, orig)
-		}
-	}
-}
-
 func TestFileDiff_Stat(t *testing.T) {
 	tests := map[string]struct {
 		hunks []*Hunk

diff/parse.go

@@ -304,6 +304,15 @@ func ParseHunks(diff []byte) ([]*Hunk, error) {
 	return hunks, nil
 }
 
+// StripModifierLines strips the modifier line "\ No newline at end of file", which
+// indicates that the preceding line has no terminating newline character. This makes it
+// so that all lines in the hunk corresponds to actual lines in the file.
+func StripModifierLines(hunks []*Hunk) {
+	for _, hunk := range hunks {
+		hunk.Body = bytes.Replace(hunk.Body, []byte(NoNewlineMessage+"\n"), []byte{}, -1)
+	}
+}
+
 // NewHunksReader returns a new HunksReader that reads unified diff hunks
 // from r.
 func NewHunksReader(r io.Reader) *HunksReader {
@@ -391,13 +400,6 @@ func (r *HunksReader) ReadHunk() (*Hunk, error) {
 				// handle that case.
 				return r.hunk, &ParseError{r.line, r.offset, &ErrBadHunkLine{Line: line}}
 			}
-			if bytes.Equal(line, []byte(noNewlineMessage)) {
-				// Remove previous line's newline.
-				if len(r.hunk.Body) != 0 {
-					r.hunk.Body = r.hunk.Body[:len(r.hunk.Body)-1]
-				}
-				continue
-			}
 
 			r.hunk.Body = append(r.hunk.Body, line...)
 			r.hunk.Body = append(r.hunk.Body, '\n')
@@ -414,7 +416,7 @@ func (r *HunksReader) ReadHunk() (*Hunk, error) {
 	return nil, io.EOF
 }
 
-const noNewlineMessage = `\ No newline at end of file`
+const NoNewlineMessage = `\ No newline at end of file`
 
 // linePrefixes is the set of all characters a valid line in a diff
 // hunk can start with. '\' can appear in diffs when no newline is

diff/print.go

@@ -89,17 +89,6 @@ func PrintHunks(hunks []*Hunk) ([]byte, error) {
 		if _, err := buf.Write(hunk.Body); err != nil {
 			return nil, err
 		}
-		if !bytes.HasSuffix(hunk.Body, []byte{'\n'}) {
-			if _, err := fmt.Fprintln(&buf); err != nil {
-				return nil, err
-			}
-			if _, err := buf.Write([]byte(noNewlineMessage)); err != nil {
-				return nil, err
-			}
-			if _, err := fmt.Fprintln(&buf); err != nil {
-				return nil, err
-			}
-		}
 	}
 	return buf.Bytes(), nil
 }

diff/testdata/oneline_hunk.diff

@@ -0,0 +1,3 @@
+@@ -1,1 +1,1 @@
+-there is an {{ identifier }} in this file
++this is a file

diff/testdata/sample_hunks_no_newline2.diff

@@ -0,0 +1,5 @@
+@@ -1,1 +1,1 @@
+-b
+\ No newline at end of file
++b
+\ No newline at end of file