all: replace build tags in tests with testenv helper

Many tool features, particularly modules-related, require particular Go
versions. Build tags are unwieldy, requiring one-off test files which
break up test organization.

Add a suite of testenv functions that check what Go version is in use.
Note that this is the logical Go version, as denoted by the release
tags; it should be updated at the beginning of the release cycle per
issue golang/go#38704.

For ease of reviewing, I'll merge/delete files in a followup CL.

Change-Id: Id85ce0f83387b3c45d68465161cf88447325d4f2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/234882
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

go/internal/gcimporter/gcimporter11_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build go1.11
-
 package gcimporter
 
 import (
@@ -11,6 +9,8 @@ import (
 	"runtime"
 	"strings"
 	"testing"
+
+	"golang.org/x/tools/internal/testenv"
 )
 
 var importedObjectTests = []struct {
@@ -38,6 +38,7 @@ var importedObjectTests = []struct {
 }
 
 func TestImportedTypes(t *testing.T) {
+	testenv.NeedsGo1Point(t, 11)
 	skipSpecialPlatforms(t)
 
 	// This package only handles gc export data.
@@ -112,6 +113,7 @@ func verifyInterfaceMethodRecvs(t *testing.T, named *types.Named, level int) {
 	}
 }
 func TestIssue25301(t *testing.T) {
+	testenv.NeedsGo1Point(t, 11)
 	skipSpecialPlatforms(t)
 
 	// This package only handles gc export data.

go/packages/packages110_test.go

@@ -1,11 +0,0 @@
-// Copyright 2018 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.
-
-// +build !go1.11
-
-package packages_test
-
-func init() {
-	usesOldGolist = true
-}

go/packages/packages114_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build go1.14
-
 package packages_test
 
 import (
@@ -13,13 +11,14 @@ import (
 
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/go/packages/packagestest"
+	"golang.org/x/tools/internal/testenv"
 )
 
 // These tests check fixes that are only available in Go 1.14.
-// They can be moved into packages_test.go when we no longer support 1.13.
 // See golang/go#35973 for more information.
 func TestInvalidFilesInOverlay(t *testing.T) { packagestest.TestAll(t, testInvalidFilesInOverlay) }
 func testInvalidFilesInOverlay(t *testing.T, exporter packagestest.Exporter) {
+	testenv.NeedsGo1Point(t, 14)
 	exported := packagestest.Export(t, exporter, []packagestest.Module{
 		{
 			Name: "golang.org/fake",

go/packages/packages115_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build go1.15
-
 package packages_test
 
 import (
@@ -16,10 +14,9 @@ import (
 )
 
 // TestInvalidFilesInXTest checks the fix for golang/go#37971.
-func TestInvalidFilesInXTest(t *testing.T) {
+func TestInvalidFilesInXTest(t *testing.T) { packagestest.TestAll(t, testInvalidFilesInXTest) }
-	packagestest.TestAll(t, testInvalidFilesInXTest)
-}
 func testInvalidFilesInXTest(t *testing.T, exporter packagestest.Exporter) {
+	testenv.NeedsGo1Point(t, 15)
 	exported := packagestest.Export(t, exporter, []packagestest.Module{
 		{
 			Name: "golang.org/fake",
@@ -44,11 +41,9 @@ func testInvalidFilesInXTest(t *testing.T, exporter packagestest.Exporter) {
 	}
 }
 
-func TestTypecheckCgo(t *testing.T) {
+func TestTypecheckCgo(t *testing.T) { packagestest.TestAll(t, testTypecheckCgo) }
-	packagestest.TestAll(t, testTypecheckCgo)
-}
-
 func testTypecheckCgo(t *testing.T, exporter packagestest.Exporter) {
+	testenv.NeedsGo1Point(t, 15)
 	testenv.NeedsTool(t, "cgo")
 
 	const cgo = `package cgo

go/packages/packagestest/modules_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build go1.11
-
 package packagestest_test
 
 import (
@@ -11,9 +9,11 @@ import (
 	"testing"
 
 	"golang.org/x/tools/go/packages/packagestest"
+	"golang.org/x/tools/internal/testenv"
 )
 
 func TestModulesExport(t *testing.T) {
+	testenv.NeedsGo1Point(t, 11)
 	exported := packagestest.Export(t, packagestest.Modules, testdata)
 	defer exported.Cleanup()
 	// Check that the cfg contains all the right bits

internal/imports/mod_112_test.go

@@ -1,14 +1,15 @@
-// +build go1.12
-
 package imports
 
 import (
 	"context"
 	"testing"
+
+	"golang.org/x/tools/internal/testenv"
 )
 
 // Tests that we handle GO111MODULE=on with no go.mod file. See #30855.
 func TestNoMainModule(t *testing.T) {
+	testenv.NeedsGo1Point(t, 12)
 	mt := setup(t, `
 -- x.go --
 package x

internal/imports/mod_114_test.go

@@ -1,11 +1,12 @@
-// +build go1.14
-
 package imports
 
 import (
 	"testing"
+
+	"golang.org/x/tools/internal/testenv"
 )
 
 func TestModVendorAuto_114(t *testing.T) {
+	testenv.NeedsGo1Point(t, 14)
 	testModVendorAuto(t, true)
 }

internal/imports/mod_pre114_test.go

@@ -1,11 +1,12 @@
-// +build !go1.14
-
 package imports
 
 import (
 	"testing"
+
+	"golang.org/x/tools/internal/testenv"
 )
 
 func TestModVendorAuto_Pre114(t *testing.T) {
+	testenv.SkipAfterGo1Point(t, 13)
 	testModVendorAuto(t, false)
 }

internal/imports/mod_test.go

@@ -1,5 +1,3 @@
-// +build go1.11
-
 package imports
 
 import (
@@ -21,6 +19,7 @@ import (
 	"golang.org/x/mod/module"
 	"golang.org/x/tools/internal/gocommand"
 	"golang.org/x/tools/internal/gopathwalk"
+	"golang.org/x/tools/internal/proxydir"
 	"golang.org/x/tools/internal/testenv"
 	"golang.org/x/tools/txtar"
 )
@@ -647,6 +646,7 @@ type modTest struct {
 // in testdata/mod, along the lines of TestScript in cmd/go.
 func setup(t *testing.T, main, wd string) *modTest {
 	t.Helper()
+	testenv.NeedsGo1Point(t, 11)
 	testenv.NeedsTool(t, "go")
 
 	proxyOnce.Do(func() {
@@ -674,7 +674,7 @@ func setup(t *testing.T, main, wd string) *modTest {
 		GOROOT:      build.Default.GOROOT,
 		GOPATH:      filepath.Join(dir, "gopath"),
 		GO111MODULE: "on",
-		GOPROXY:     proxyDirToURL(proxyDir),
+		GOPROXY:     proxydir.ToURL(proxyDir),
 		GOSUMDB:     "off",
 		WorkingDir:  filepath.Join(mainDir, wd),
 		GocmdRunner: &gocommand.Runner{},
@@ -834,6 +834,7 @@ import _ "rsc.io/quote"
 
 // Tests that crud in the module cache is ignored.
 func TestInvalidModCache(t *testing.T) {
+	testenv.NeedsGo1Point(t, 11)
 	dir, err := ioutil.TempDir("", t.Name())
 	if err != nil {
 		t.Fatal(err)
@@ -920,6 +921,7 @@ import _ "rsc.io/quote"
 }
 
 func BenchmarkScanModCache(b *testing.B) {
+	testenv.NeedsGo1Point(b, 11)
 	env := &ProcessEnv{
 		GOPATH:      build.Default.GOPATH,
 		GOROOT:      build.Default.GOROOT,

internal/imports/proxy_112_test.go

@@ -1,20 +0,0 @@
-// +build !go1.13
-
-// 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 imports
-
-import "path/filepath"
-
-// TODO: use proxy functionality in golang.org/x/tools/go/packages/packagestest
-// instead of copying it here.
-
-func proxyDirToURL(dir string) string {
-	// Prior to go1.13, the Go command on Windows only accepted GOPROXY file URLs
-	// of the form file://C:/path/to/proxy. This was incorrect: when parsed, "C:"
-	// is interpreted as the host. See golang.org/issue/6027. This has been
-	// fixed in go1.13, but we emit the old format for old releases.
-	return "file://" + filepath.ToSlash(dir)
-}

internal/imports/proxy_113_test.go

@@ -1,24 +0,0 @@
-// +build go1.13
-
-// Copyright 2018 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 imports
-
-import (
-	"path/filepath"
-	"strings"
-)
-
-// TODO: use proxy functionality in golang.org/x/tools/go/packages/packagestest
-// instead of copying it here.
-
-func proxyDirToURL(dir string) string {
-	// file URLs on Windows must start with file:///. See golang.org/issue/6027.
-	path := filepath.ToSlash(dir)
-	if !strings.HasPrefix(path, "/") {
-		path = "/" + path
-	}
-	return "file://" + path
-}

internal/lsp/regtest/diagnostics_114_test.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build go1.14
-
 package regtest
 
 import (
@@ -12,6 +10,7 @@ import (
 	"golang.org/x/tools/internal/lsp"
 	"golang.org/x/tools/internal/lsp/fake"
 	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/testenv"
 )
 
 const ardanLabsProxy = `
@@ -28,6 +27,7 @@ var ErrHelpWanted error
 // -modfile flag that is used to provide modfile diagnostics is only available
 // with 1.14.
 func Test_Issue38211(t *testing.T) {
+	testenv.NeedsGo1Point(t, 14)
 	const ardanLabs = `
 -- go.mod --
 module mod.com
@@ -91,6 +91,7 @@ func main() {
 
 // Test for golang/go#38207.
 func TestNewModule_Issue38207(t *testing.T) {
+	testenv.NeedsGo1Point(t, 14)
 	const emptyFile = `
 -- go.mod --
 module mod.com
@@ -125,6 +126,7 @@ func main() {
 }
 
 func TestNewFileBadImports_Issue36960(t *testing.T) {
+	testenv.NeedsGo1Point(t, 14)
 	const simplePackage = `
 -- go.mod --
 module mod.com

internal/proxydir/proxydir_112.go

@@ -1,18 +0,0 @@
-// +build !go1.13
-
-// Copyright 2020 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 proxydir
-
-import "path/filepath"
-
-// ToURL returns the file uri for a proxy directory.
-func ToURL(dir string) string {
-	// Prior to go1.13, the Go command on Windows only accepted GOPROXY file URLs
-	// of the form file://C:/path/to/proxy. This was incorrect: when parsed, "C:"
-	// is interpreted as the host. See golang.org/issue/6027. This has been
-	// fixed in go1.13, but we emit the old format for old releases.
-	return "file://" + filepath.ToSlash(dir)
-}

internal/proxydir/proxydir_113.go

@@ -1,5 +1,3 @@
-// +build go1.13
-
 // Copyright 2020 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.
@@ -9,14 +7,24 @@ package proxydir
 import (
 	"path/filepath"
 	"strings"
+
+	"golang.org/x/tools/internal/testenv"
 )
 
 // ToURL returns the file uri for a proxy directory.
 func ToURL(dir string) string {
-	// file URLs on Windows must start with file:///. See golang.org/issue/6027.
+	if testenv.Go1Point() >= 13 {
-	path := filepath.ToSlash(dir)
+		// file URLs on Windows must start with file:///. See golang.org/issue/6027.
-	if !strings.HasPrefix(path, "/") {
+		path := filepath.ToSlash(dir)
-		path = "/" + path
+		if !strings.HasPrefix(path, "/") {
+			path = "/" + path
+		}
+		return "file://" + path
+	} else {
+		// Prior to go1.13, the Go command on Windows only accepted GOPROXY file URLs
+		// of the form file://C:/path/to/proxy. This was incorrect: when parsed, "C:"
+		// is interpreted as the host. See golang.org/issue/6027. This has been
+		// fixed in go1.13, but we emit the old format for old releases.
+		return "file://" + filepath.ToSlash(dir)
 	}
-	return "file://" + path
 }

internal/testenv/testenv.go

@@ -9,6 +9,7 @@ package testenv
 import (
 	"bytes"
 	"fmt"
+	"go/build"
 	"io/ioutil"
 	"os"
 	"os/exec"
@@ -233,3 +234,37 @@ func ExitIfSmallMachine() {
 		os.Exit(0)
 	}
 }
+
+// Go1Point returns the x in Go 1.x.
+func Go1Point() int {
+	for i := len(build.Default.ReleaseTags) - 1; i >= 0; i-- {
+		var version int
+		if _, err := fmt.Sscanf(build.Default.ReleaseTags[i], "go1.%d", &version); err != nil {
+			continue
+		}
+		return version
+	}
+	panic("bad release tags")
+}
+
+// NeedsGo1Point skips t if the Go version used to run the test is older than
+// 1.x.
+func NeedsGo1Point(t Testing, x int) {
+	if t, ok := t.(helperer); ok {
+		t.Helper()
+	}
+	if Go1Point() < x {
+		t.Skipf("running Go version %q is version 1.%d, older than required 1.%d", runtime.Version(), Go1Point(), x)
+	}
+}
+
+// SkipAfterGo1Point skips t if the Go version used to run the test is newer than
+// 1.x.
+func SkipAfterGo1Point(t Testing, x int) {
+	if t, ok := t.(helperer); ok {
+		t.Helper()
+	}
+	if Go1Point() > x {
+		t.Skipf("running Go version %q is version 1.%d, newer than maximum 1.%d", runtime.Version(), Go1Point(), x)
+	}
+}