internal/imports: suggest x for x_tests

golang.org/cl/170238 forgot that it's okay for an x_test to import a
package in the same directory. Only skip the candidate if the package
we're looking for has the same name as the one being fixed.

Fixes golang/go#32440

Change-Id: I7806d9f4174ca217ac83887da5e23b28cd102095
Reviewed-on: https://go-review.googlesource.com/c/tools/+/181338
Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/imports/fix.go

@@ -702,7 +702,7 @@ func addExternalCandidates(pass *pass, refs references, filename string) error {
 		go func(pkgName string, symbols map[string]bool) {
 			defer wg.Done()
 
-			found, err := findImport(ctx, pass.env, dirScan, pkgName, symbols, filename)
+			found, err := findImport(ctx, pass, dirScan, pkgName, symbols, filename)
 
 			if err != nil {
 				firstErrOnce.Do(func() {
@@ -1028,7 +1028,7 @@ func loadExports(ctx context.Context, env *ProcessEnv, expectPackage string, pkg
 
 // findImport searches for a package with the given symbols.
 // If no package is found, findImport returns ("", false, nil)
-func findImport(ctx context.Context, env *ProcessEnv, dirScan []*pkg, pkgName string, symbols map[string]bool, filename string) (*pkg, error) {
+func findImport(ctx context.Context, pass *pass, dirScan []*pkg, pkgName string, symbols map[string]bool, filename string) (*pkg, error) {
 	pkgDir, err := filepath.Abs(filename)
 	if err != nil {
 		return nil, err
@@ -1038,7 +1038,12 @@ func findImport(ctx context.Context, env *ProcessEnv, dirScan []*pkg, pkgName st
 	// Find candidate packages, looking only at their directory names first.
 	var candidates []pkgDistance
 	for _, pkg := range dirScan {
-		if pkg.dir != pkgDir && pkgIsCandidate(filename, pkgName, pkg) {
+		if pkg.dir == pkgDir && pass.f.Name.Name == pkgName {
+			// The candidate is in the same directory and has the
+			// same package name. Don't try to import ourselves.
+			continue
+		}
+		if pkgIsCandidate(filename, pkgName, pkg) {
 			candidates = append(candidates, pkgDistance{
 				pkg:      pkg,
 				distance: distance(pkgDir, pkg.dir),
@@ -1051,7 +1056,7 @@ func findImport(ctx context.Context, env *ProcessEnv, dirScan []*pkg, pkgName st
 	// ones.  Note that this sorts by the de-vendored name, so
 	// there's no "penalty" for vendoring.
 	sort.Sort(byDistanceOrImportPathShortLength(candidates))
-	if env.Debug {
+	if pass.env.Debug {
 		for i, c := range candidates {
 			log.Printf("%s candidate %d/%d: %v in %v", pkgName, i+1, len(candidates), c.pkg.importPathShort, c.pkg.dir)
 		}
@@ -1090,9 +1095,9 @@ func findImport(ctx context.Context, env *ProcessEnv, dirScan []*pkg, pkgName st
 					wg.Done()
 				}()
 
-				exports, err := loadExports(ctx, env, pkgName, c.pkg)
+				exports, err := loadExports(ctx, pass.env, pkgName, c.pkg)
 				if err != nil {
-					if env.Debug {
+					if pass.env.Debug {
 						log.Printf("loading exports in dir %s (seeking package %s): %v", c.pkg.dir, pkgName, err)
 					}
 					resc <- nil

internal/imports/fix_test.go

@@ -2116,6 +2116,32 @@ const _ = pkg.X
 	}.processTest(t, "foo.com", "pkg/b.go", nil, nil, want)
 }
 
+func TestExternalTestImportsPackageUnderTest(t *testing.T) {
+	const provide = `package pkg
+func DoIt(){}
+`
+	const input = `package pkg_test
+
+var _ = pkg.DoIt`
+
+	const want = `package pkg_test
+
+import "foo.com/pkg"
+
+var _ = pkg.DoIt
+`
+
+	testConfig{
+		module: packagestest.Module{
+			Name: "foo.com",
+			Files: fm{
+				"pkg/provide.go": provide,
+				"pkg/x_test.go":  input,
+			},
+		},
+	}.processTest(t, "foo.com", "pkg/x_test.go", nil, nil, want)
+}
+
 func TestPkgIsCandidate(t *testing.T) {
 	tests := []struct {
 		name     string