cmd/go/internal/work: remove '_test' from import paths in stacktraces when -trimpath is specified

ExampleFrames with -trimpath failed since the content of Frame's File
changed when -trimpath is specified.

This CL fixes the issue by adding a new field OrigImportPath to
PackageInternal, which represents the original import path before adding
'_test' suffix for an external test package, and always using it to
create paths for the build tools.

Fixes golang/go#43380

Change-Id: Ibbc947eb3ae08a7ba81f13f03af67c8745b5c69f
Reviewed-on: https://go-review.googlesource.com/c/go/+/279440
Run-TryBot: Hajime Hoshi <hajimehoshi@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Hajime Hoshi <hajimehoshi@gmail.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/load/pkg.go

@@ -207,6 +207,7 @@ type PackageInternal struct {
 	BuildInfo         string               // add this info to package main
 	TestmainGo        *[]byte              // content for _testmain.go
 	Embed             map[string][]string  // //go:embed comment mapping
+	OrigImportPath    string               // original import path before adding '_test' suffix
 
 	Asmflags   []string // -asmflags for this package
 	Gcflags    []string // -gcflags for this package
@@ -402,6 +403,7 @@ func (p *Package) copyBuild(pp *build.Package) {
 	p.EmbedPatterns = pp.EmbedPatterns
 	p.TestEmbedPatterns = pp.TestEmbedPatterns
 	p.XTestEmbedPatterns = pp.XTestEmbedPatterns
+	p.Internal.OrigImportPath = pp.ImportPath
 }
 
 // A PackageError describes an error loading information about a package.

src/cmd/go/internal/load/test.go

@@ -204,6 +204,7 @@ func TestPackagesAndErrors(ctx context.Context, p *Package, cover *TestCover) (p
 		}
 		ptest.Internal.Embed = testEmbed
 		ptest.EmbedFiles = str.StringList(p.EmbedFiles, p.TestEmbedFiles)
+		ptest.Internal.OrigImportPath = p.Internal.OrigImportPath
 		ptest.collectDeps()
 	} else {
 		ptest = p
@@ -238,6 +239,7 @@ func TestPackagesAndErrors(ctx context.Context, p *Package, cover *TestCover) (p
 				Ldflags:        p.Internal.Ldflags,
 				Gccgoflags:     p.Internal.Gccgoflags,
 				Embed:          xtestEmbed,
+				OrigImportPath: p.Internal.OrigImportPath,
 			},
 		}
 		if pxtestNeedsPtest {
@@ -264,6 +266,7 @@ func TestPackagesAndErrors(ctx context.Context, p *Package, cover *TestCover) (p
 			Gcflags:        p.Internal.Gcflags,
 			Ldflags:        p.Internal.Ldflags,
 			Gccgoflags:     p.Internal.Gccgoflags,
+			OrigImportPath: p.Internal.OrigImportPath,
 		},
 	}
 

src/cmd/go/internal/work/gc.go

@@ -290,10 +290,11 @@ func (a *Action) trimpath() string {
 
 	rewriteDir := a.Package.Dir
 	if cfg.BuildTrimpath {
+		importPath := a.Package.Internal.OrigImportPath
 		if m := a.Package.Module; m != nil && m.Version != "" {
-			rewriteDir = m.Path + "@" + m.Version + strings.TrimPrefix(a.Package.ImportPath, m.Path)
+			rewriteDir = m.Path + "@" + m.Version + strings.TrimPrefix(importPath, m.Path)
 		} else {
-			rewriteDir = a.Package.ImportPath
+			rewriteDir = importPath
 		}
 		rewrite += a.Package.Dir + "=>" + rewriteDir + ";"
 	}

src/cmd/go/testdata/script/test_trimpath.txt

@@ -0,0 +1,51 @@
+[short] skip
+
+go test -trimpath -v .
+! stdout '[/\\]pkg_test[/\\]'
+stdout -count=3 '[/\\]pkg[/\\]'
+
+-- go.mod --
+module example.com/pkg
+
+go 1.17
+
+-- pkg.go --
+package pkg
+
+import "runtime"
+
+func PrintFile() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+-- pkg_test.go --
+package pkg
+
+import "runtime"
+
+func PrintFileForTest() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+-- pkg_x_test.go --
+package pkg_test
+
+import (
+	"runtime"
+	"testing"
+
+	"example.com/pkg"
+)
+
+func TestMain(m *testing.M) {
+	pkg.PrintFile()
+	pkg.PrintFileForTest()
+	PrintFileInXTest()
+}
+
+func PrintFileInXTest() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}

src/cmd/go/testdata/script/test_trimpath_main.txt

@@ -0,0 +1,38 @@
+[short] skip
+
+go test -trimpath -v .
+! stdout '[/\\]pkg_test[/\\]'
+stdout -count=2 '[/\\]pkg[/\\]'
+
+-- go.mod --
+module example.com/pkg
+
+go 1.17
+
+-- main.go --
+package main
+
+import "runtime"
+
+func PrintFile() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+-- main_test.go --
+package main
+
+import (
+	"runtime"
+	"testing"
+)
+
+func PrintFileForTest() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+func TestMain(m *testing.M) {
+	PrintFile()
+	PrintFileForTest()
+}

src/cmd/go/testdata/script/test_trimpath_test_suffix.txt

@@ -0,0 +1,40 @@
+[short] skip
+
+go test -trimpath -v .
+! stdout '[/\\]pkg_test_test[/\\]'
+stdout -count=2 '[/\\]pkg_test[/\\]'
+
+-- go.mod --
+module example.com/pkg_test
+
+go 1.17
+
+-- pkg.go --
+package pkg_test
+
+import "runtime"
+
+func PrintFile() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+-- pkg_x_test.go --
+package pkg_test_test
+
+import (
+	"runtime"
+	"testing"
+
+	"example.com/pkg_test"
+)
+
+func PrintFileForTest() {
+	_, file, _, _ := runtime.Caller(0)
+	println(file)
+}
+
+func TestMain(m *testing.M) {
+	pkg_test.PrintFile()
+	PrintFileForTest()
+}