internal/lsp: move unified diff testing to the diff interface

This now checks at the diff.TextEdit layer rather than myers.Op Change-Id: I706657a6c5705f0ad7109aa81f4dce174dda5f2b Reviewed-on: https://go-review.googlesource.com/c/tools/+/198380 Run-TryBot: Ian Cottrell <iancottrell@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rebecca Stambler <rstambler@golang.org>

Author: ianthehat

internal/lsp/diff/difftest/difftest.go

@@ -8,44 +8,209 @@
 package difftest
 
 import (
+"flag"
+"fmt"
+"io/ioutil"
+"os"
+"os/exec"
+"strings"
 "testing"
 
 "golang.org/x/tools/internal/lsp/diff"
 "golang.org/x/tools/internal/span"
 )
 
+const (
+fileA = "from"
+fileB = "to"
+unifiedPrefix = "--- " + fileA + "\n+++ " + fileB + "\n"
+)
+
+var verifyDiff = flag.Bool("verify-diff", false, "Check that the unified diff output matches `diff -u`")
+
 func DiffTest(t *testing.T, compute diff.ComputeEdits) {
 t.Helper()
-for _, test := range []struct{ name, in, out, unified string }{{
+for _, test := range []struct {
+name, in, out, unified string
+nodiff bool
+}{{
 name: "empty",
 in: "",
 out: "",
 }, {
 name: "no_diff",
-in: "gargantuan",
-out: "gargantuan",
+in: "gargantuan\n",
+out: "gargantuan\n",
+}, {
+name: "replace_all",
+in: "gord\n",
+out: "gourd\n",
+unified: unifiedPrefix + `
+@@ -1 +1 @@
+-gord
++gourd
+`[1:],
 }, {
 name: "insert_rune",
-in: "gord",
-out: "gourd",
+in: "gord\n",
+out: "gourd\n",
+unified: unifiedPrefix + `
+@@ -1 +1 @@
+-gord
++gourd
+`[1:],
 }, {
 name: "delete_rune",
-in: "groat",
-out: "goat",
+in: "groat\n",
+out: "goat\n",
+unified: unifiedPrefix + `
+@@ -1 +1 @@
+-groat
++goat
+`[1:],
 }, {
 name: "replace_rune",
-in: "loud",
-out: "lord",
+in: "loud\n",
+out: "lord\n",
+unified: unifiedPrefix + `
+@@ -1 +1 @@
+-loud
++lord
+`[1:],
 }, {
 name: "insert_line",
 in: "one\nthree\n",
 out: "one\ntwo\nthree\n",
-}} {
-edits := compute(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)
+unified: unifiedPrefix + `
+@@ -1,2 +1,3 @@
+ one
++two
+ three
+`[1:],
+}, {
+name: "replace_no_newline",
+in: "A",
+out: "B",
+unified: unifiedPrefix + `
+@@ -1 +1 @@
+-A
+\ No newline at end of file
++B
+\ No newline at end of file
+`[1:],
+}, {
+name: "delete_front",
+in: "A\nB\nC\nA\nB\nB\nA\n",
+out: "C\nB\nA\nB\nA\nC\n",
+unified: unifiedPrefix + `
+@@ -1,7 +1,6 @@
+-A
+-B
+ C
++B
+ A
+ B
+-B
+ A
++C
+`[1:],
+nodiff: true, // diff algorithm produces different delete/insert pattern
+},
+{
+name: "replace_last_line",
+in: "A\nB\n",
+out: "A\nC\n\n",
+unified: unifiedPrefix + `
+@@ -1,2 +1,3 @@
+ A
+-B
++C
++
+`[1:],
+},
+{
+name: "mulitple_replace",
+in: "A\nB\nC\nD\nE\nF\nG\n",
+out: "A\nH\nI\nJ\nE\nF\nK\n",
+unified: unifiedPrefix + `
+@@ -1,7 +1,7 @@
+ A
+-B
+-C
+-D
++H
++I
++J
+ E
+ F
+-G
++K
+`[1:],
+}} {
+t.Run(test.name, func(t *testing.T) {
+t.Helper()
+edits := compute(span.FileURI("/"+test.name), test.in, test.out)
+got := diff.ApplyEdits(test.in, edits)
+unified := diff.ToUnified("from", "to", test.in, edits)
+if got != test.out {
+t.Errorf("got patched:\n%v\nfrom diff:\n%v\nexpected:\n%v", got, unified, test.out)
+}
+if unified != test.unified {
+t.Errorf("got diff:\n%v\nexpected:\n%v", unified, test.unified)
+}
+if *verifyDiff && !test.nodiff {
+diff, err := getDiffOutput(test.in, test.out)
+if err != nil {
+t.Fatal(err)
+}
+if len(diff) > 0 {
+diff = unifiedPrefix + diff
+}
+if diff != test.unified {
+t.Errorf("unified:\n%q\ndiff -u:\n%q", test.unified, diff)
+}
+}
+})
+}
+}
+
+func getDiffOutput(a, b string) (string, error) {
+fileA, err := ioutil.TempFile("", "myers.in")
+if err != nil {
+return "", err
+}
+defer os.Remove(fileA.Name())
+if _, err := fileA.Write([]byte(a)); err != nil {
+return "", err
+}
+if err := fileA.Close(); err != nil {
+return "", err
+}
+fileB, err := ioutil.TempFile("", "myers.in")
+if err != nil {
+return "", err
+}
+defer os.Remove(fileB.Name())
+if _, err := fileB.Write([]byte(b)); err != nil {
+return "", err
+}
+if err := fileB.Close(); err != nil {
+return "", err
+}
+cmd := exec.Command("diff", "-u", fileA.Name(), fileB.Name())
+out, err := cmd.CombinedOutput()
+if err != nil {
+if _, ok := err.(*exec.ExitError); !ok {
+return "", fmt.Errorf("failed to run diff -u %v %v: %v\n%v", fileA.Name(), fileB.Name(), err, string(out))
 }
 }
+diff := string(out)
+if len(diff) <= 0 {
+return diff, nil
+}
+bits := strings.SplitN(diff, "\n", 3)
+if len(bits) != 3 {
+return "", fmt.Errorf("diff output did not have file prefix:\n%s", diff)
+}
+return bits[2], nil
 }