internal/lsp: add tests at the diff hook layer
this makes sure that any diff implementation obeys the semantics we expect
at higher layers
Change-Id: Iae8842cfb9fece94ea71c04ec146d825eff0cbeb
Reviewed-on: https://go-review.googlesource.com/c/tools/+/191017
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
diff --git a/internal/lsp/diff/diff_test.go b/internal/lsp/diff/diff_test.go
new file mode 100644
index 0000000..be7965b
--- /dev/null
+++ b/internal/lsp/diff/diff_test.go
@@ -0,0 +1,15 @@
+// Copyright 2019 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 diff_test
+
+import (
+ "testing"
+
+ "golang.org/x/tools/internal/lsp/diff/difftest"
+)
+
+func TestDiff(t *testing.T) {
+ difftest.DiffTest(t)
+}
diff --git a/internal/lsp/diff/difftest/difftest.go b/internal/lsp/diff/difftest/difftest.go
new file mode 100644
index 0000000..f7db02d
--- /dev/null
+++ b/internal/lsp/diff/difftest/difftest.go
@@ -0,0 +1,51 @@
+// Copyright 2019 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 difftest supplies a set of tests that will operate on any
+// implementation of a diff algorithm as exposed by
+// "golang.org/x/tools/internal/lsp/diff"
+package difftest
+
+import (
+ "testing"
+
+ "golang.org/x/tools/internal/lsp/diff"
+ "golang.org/x/tools/internal/span"
+)
+
+func DiffTest(t *testing.T) {
+ t.Helper()
+ for _, test := range []struct{ name, in, out, unified string }{{
+ name: "empty",
+ in: "",
+ out: "",
+ }, {
+ name: "no_diff",
+ in: "gargantuan",
+ out: "gargantuan",
+ }, {
+ name: "insert_rune",
+ in: "gord",
+ out: "gourd",
+ }, {
+ name: "delete_rune",
+ in: "groat",
+ out: "goat",
+ }, {
+ name: "replace_rune",
+ in: "loud",
+ out: "lord",
+ }, {
+ name: "insert_line",
+ in: "one\nthree\n",
+ out: "one\ntwo\nthree\n",
+ }} {
+ edits := diff.ComputeEdits(span.FileURI("/"+test.name), test.in, test.out)
+ got := diff.ApplyEdits(test.in, edits)
+ if got != test.out {
+ t.Logf("test %v had diff:%v\n", test.name, diff.ToUnified(test.name+".orig", test.name, test.in, edits))
+ t.Errorf("diff %v got:\n%v\nexpected:\n%v", test.name, got, test.out)
+ }
+ }
+}
diff --git a/internal/lsp/diff/myers/diff.go b/internal/lsp/diff/myers/diff.go
index ddf04ca..8c2daeb 100644
--- a/internal/lsp/diff/myers/diff.go
+++ b/internal/lsp/diff/myers/diff.go
@@ -67,6 +67,10 @@
// Operations returns the list of operations to convert a into b, consolidating
// operations for multiple lines and not including equal lines.
func Operations(a, b []string) []*Op {
+ if len(a) == 0 && len(b) == 0 {
+ return nil
+ }
+
trace, offset := shortestEditSequence(a, b)
snakes := backtrack(trace, len(a), len(b), offset)
