go/ssa/ssautil: use go/packages to load packages in switch_test.go

Updates golang/go#69556

Change-Id: I5459a835b96f6f79d193538fdbc85a3e1c7324cc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/615035
LUCI-TryBot-Result: Go LUCI <[email protected]>
Commit-Queue: Tim King <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Tim King <[email protected]>

Author: xieyuschen

go/ssa/ssautil/switch_test.go

@@ -10,18 +10,43 @@
 package ssautil_test
 
 import (
+	"go/ast"
 	"go/parser"
+	"path/filepath"
 	"strings"
 	"testing"
 
 	"golang.org/x/tools/go/loader"
 	"golang.org/x/tools/go/ssa"
 	"golang.org/x/tools/go/ssa/ssautil"
+	"golang.org/x/tools/internal/testfiles"
+	"golang.org/x/tools/txtar"
 )
 
 func TestSwitches(t *testing.T) {
+	archive, err := txtar.ParseFile("testdata/switches.txtar")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ppkgs := testfiles.LoadPackages(t, archive, ".")
+	if len(ppkgs) != 1 {
+		t.Fatalf("Expected to load one package but got %d", len(ppkgs))
+	}
+
+	prog, _ := ssautil.Packages(ppkgs, ssa.BuilderMode(0))
+	mainPkg := prog.Package(ppkgs[0].Types)
+	mainPkg.Build()
+	testSwitches(t, ppkgs[0].Syntax[0], mainPkg)
+}
+
+// TestCreateProgram uses loader and ssautil.CreateProgram to create an *ssa.Program.
+// It has the same testing logic with TestSwitches.
+// CreateProgram is deprecated, but it is a part of the public API.
+// For now keep a test that exercises it.
+func TestCreateProgram(t *testing.T) {
+	dir := testfiles.ExtractTxtarFileToTmp(t, "testdata/switches.txtar")
 	conf := loader.Config{ParserMode: parser.ParseComments}
-	f, err := conf.ParseFile("testdata/switches.go", nil)
+	f, err := conf.ParseFile(filepath.Join(dir, "switches.go"), nil)
 	if err != nil {
 		t.Error(err)
 		return
@@ -33,11 +58,13 @@ func TestSwitches(t *testing.T) {
 		t.Error(err)
 		return
 	}
-
 	prog := ssautil.CreateProgram(iprog, ssa.BuilderMode(0))
 	mainPkg := prog.Package(iprog.Created[0].Pkg)
 	mainPkg.Build()
+	testSwitches(t, f, mainPkg)
+}
 
+func testSwitches(t *testing.T, f *ast.File, mainPkg *ssa.Package) {
 	for _, mem := range mainPkg.Members {
 		if fn, ok := mem.(*ssa.Function); ok {
 			if fn.Synthetic != "" {

go/ssa/ssautil/testdata/switches.go renamed to go/ssa/ssautil/testdata/switches.txtar

@@ -1,5 +1,8 @@
-// +build ignore
+-- go.mod --
+module example.com
+go 1.22
 
+-- switches.go --
 package main
 
 // This file is the input to TestSwitches in switch_test.go.