From ea34aaf6e5fa56114d47ce08d5eb31ba3fb68d6f Mon Sep 17 00:00:00 2001
From: Chris Drew <chris@cdrew.co.uk>
Date: Sun, 10 Feb 2019 14:55:59 +0000
Subject: [PATCH] Handle diffs on windows

Running the standard diff tool on windows
produces output with CRLF line endings.
Stripping trailing CR in the line reader utility
prevents errors in diff parsing.
---
 diff/diff_test.go                            | 38 +++++++++++
 diff/reader_util.go                          | 13 +++-
 diff/reader_util_test.go                     | 68 ++++++++++++++++++++
 diff/testdata/sample_multi_file_new_win.diff | 27 ++++++++
 4 files changed, 143 insertions(+), 3 deletions(-)
 create mode 100644 diff/reader_util_test.go
 create mode 100644 diff/testdata/sample_multi_file_new_win.diff

diff --git a/diff/diff_test.go b/diff/diff_test.go
index 6982239..7883180 100644
--- a/diff/diff_test.go
+++ b/diff/diff_test.go
@@ -375,6 +375,44 @@ func TestParseMultiFileDiffHeaders(t *testing.T) {
 				},
 			},
 		},
+		{
+			filename: "sample_multi_file_new_win.diff",
+			wantDiffs: []*FileDiff{
+				{
+					OrigName: "/dev/null",
+					OrigTime: nil,
+					NewName:  "b/_vendor/go/build/syslist_test.go",
+					NewTime:  nil,
+					Extended: []string{
+						"diff --git a/_vendor/go/build/syslist_test.go b/_vendor/go/build/syslist_test.go",
+						"new file mode 100644",
+						"index 0000000..3be2928",
+					},
+				},
+				{
+					OrigName: "/dev/null",
+					OrigTime: nil,
+					NewName:  "b/_vendor/go/build/testdata/empty/dummy",
+					NewTime:  nil,
+					Extended: []string{
+						"diff --git a/_vendor/go/build/testdata/empty/dummy b/_vendor/go/build/testdata/empty/dummy",
+						"new file mode 100644",
+						"index 0000000..e69de29",
+					},
+				},
+				{
+					OrigName: "/dev/null",
+					OrigTime: nil,
+					NewName:  "b/_vendor/go/build/testdata/multi/file.go",
+					NewTime:  nil,
+					Extended: []string{
+						"diff --git a/_vendor/go/build/testdata/multi/file.go b/_vendor/go/build/testdata/multi/file.go",
+						"new file mode 100644",
+						"index 0000000..ee946eb",
+					},
+				},
+			},
+		},
 	}
 	for _, test := range tests {
 		diffData, err := ioutil.ReadFile(filepath.Join("testdata", test.filename))
diff --git a/diff/reader_util.go b/diff/reader_util.go
index 7674424..395fb7b 100644
--- a/diff/reader_util.go
+++ b/diff/reader_util.go
@@ -2,7 +2,6 @@ package diff
 
 import (
 	"bufio"
-	"bytes"
 	"io"
 )
 
@@ -25,6 +24,14 @@ func readLine(r *bufio.Reader) ([]byte, error) {
 	} else if err != nil {
 		return nil, err
 	}
-	line := bytes.TrimSuffix(line_, []byte{'\n'})
-	return line, nil
+	line := line_[0 : len(line_)-1]
+	return dropCR(line), nil
+}
+
+// dropCR drops a terminal \r from the data.
+func dropCR(data []byte) []byte {
+	if len(data) > 0 && data[len(data)-1] == '\r' {
+		return data[0 : len(data)-1]
+	}
+	return data
 }
diff --git a/diff/reader_util_test.go b/diff/reader_util_test.go
new file mode 100644
index 0000000..8d5b2b7
--- /dev/null
+++ b/diff/reader_util_test.go
@@ -0,0 +1,68 @@
+package diff
+
+import (
+	"bufio"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestReadLine(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  []string
+	}{
+		{
+			name:  "empty",
+			input: "",
+			want:  []string{},
+		},
+		{
+			name:  "single_line",
+			input: "@@ -0,0 +1,62 @@",
+			want:  []string{"@@ -0,0 +1,62 @@"},
+		},
+		{
+			name:  "single_lf_terminated_line",
+			input: "@@ -0,0 +1,62 @@\n",
+			want:  []string{"@@ -0,0 +1,62 @@"},
+		},
+		{
+			name:  "single_crlf_terminated_line",
+			input: "@@ -0,0 +1,62 @@\r\n",
+			want:  []string{"@@ -0,0 +1,62 @@"},
+		},
+		{
+			name: "multi_line",
+			input: `diff --git a/test.go b/test.go
+new file mode 100644
+index 0000000..3be2928`,
+			want: []string{
+				"diff --git a/test.go b/test.go",
+				"new file mode 100644",
+				"index 0000000..3be2928",
+			},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			in := bufio.NewReader(strings.NewReader(test.input))
+			out := []string{}
+			for {
+				l, err := readLine(in)
+				if err == io.EOF {
+					break
+				}
+				if err != nil {
+					t.Fatal(err)
+				}
+				out = append(out, string(l))
+			}
+			if !reflect.DeepEqual(test.want, out) {
+				t.Errorf("read lines not equal: want %v, got %v", test.want, out)
+			}
+		})
+	}
+}
diff --git a/diff/testdata/sample_multi_file_new_win.diff b/diff/testdata/sample_multi_file_new_win.diff
new file mode 100644
index 0000000..b5e1788
--- /dev/null
+++ b/diff/testdata/sample_multi_file_new_win.diff
@@ -0,0 +1,27 @@
+diff --git a/_vendor/go/build/syslist_test.go b/_vendor/go/build/syslist_test.go
+new file mode 100644
+index 0000000..3be2928
+--- /dev/null
++++ b/_vendor/go/build/syslist_test.go
+@@ -0,0 +1,62 @@
++func TestGoodOSArch(t *testing.T) {
++	for _, test := range tests {
++		if Default.goodOSArchFile(test.name, make(map[string]bool)) != test.result {
++			t.Fatalf("goodOSArchFile(%q) != %v", test.name, test.result)
++		}
++	}
++}
+diff --git a/_vendor/go/build/testdata/empty/dummy b/_vendor/go/build/testdata/empty/dummy
+new file mode 100644
+index 0000000..e69de29
+diff --git a/_vendor/go/build/testdata/multi/file.go b/_vendor/go/build/testdata/multi/file.go
+new file mode 100644
+index 0000000..ee946eb
+--- /dev/null
++++ b/_vendor/go/build/testdata/multi/file.go
+@@ -0,0 +1,5 @@
++// Test data - not compiled.
++
++package main
++
++func main() {}