1 files changed, 96 insertions, 0 deletions
diff --git a/gopls/internal/lsp/fake/edit_test.go b/gopls/internal/lsp/fake/edit_test.go
new file mode 100644
index 000000000..97e2c73e4
--- /dev/null
+++ b/gopls/internal/lsp/fake/edit_test.go
@@ -0,0 +1,96 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fake
+
+import (
+	"testing"
+
+	"golang.org/x/tools/gopls/internal/lsp/protocol"
+)
+
+func TestApplyEdits(t *testing.T) {
+	tests := []struct {
+		label   string
+		content string
+		edits   []protocol.TextEdit
+		want    string
+		wantErr bool
+	}{
+		{
+			label: "empty content",
+		},
+		{
+			label:   "empty edit",
+			content: "hello",
+			edits:   []protocol.TextEdit{},
+			want:    "hello",
+		},
+		{
+			label:   "unicode edit",
+			content: "hello, 日本語",
+			edits: []protocol.TextEdit{
+				NewEdit(0, 7, 0, 10, "world"),
+			},
+			want: "hello, world",
+		},
+		{
+			label:   "range edit",
+			content: "ABC\nDEF\nGHI\nJKL",
+			edits: []protocol.TextEdit{
+				NewEdit(1, 1, 2, 3, "12\n345"),
+			},
+			want: "ABC\nD12\n345\nJKL",
+		},
+		{
+			label:   "regression test for issue #57627",
+			content: "go 1.18\nuse moda/a",
+			edits: []protocol.TextEdit{
+				NewEdit(1, 0, 1, 0, "\n"),
+				NewEdit(2, 0, 2, 0, "\n"),
+			},
+			want: "go 1.18\n\nuse moda/a\n",
+		},
+		{
+			label:   "end before start",
+			content: "ABC\nDEF\nGHI\nJKL",
+			edits: []protocol.TextEdit{
+				NewEdit(2, 3, 1, 1, "12\n345"),
+			},
+			wantErr: true,
+		},
+		{
+			label:   "out of bounds line",
+			content: "ABC\nDEF\nGHI\nJKL",
+			edits: []protocol.TextEdit{
+				NewEdit(1, 1, 4, 3, "12\n345"),
+			},
+			wantErr: true,
+		},
+		{
+			label:   "out of bounds column",
+			content: "ABC\nDEF\nGHI\nJKL",
+			edits: []protocol.TextEdit{
+				NewEdit(1, 4, 2, 3, "12\n345"),
+			},
+			wantErr: true,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.label, func(t *testing.T) {
+			got, err := applyEdits(protocol.NewMapper("", []byte(test.content)), test.edits, false)
+			if (err != nil) != test.wantErr {
+				t.Errorf("got err %v, want error: %t", err, test.wantErr)
+			}
+			if err != nil {
+				return
+			}
+			if got := string(got); got != test.want {
+				t.Errorf("got %q, want %q", got, test.want)
+			}
+		})
+	}
+}