cmd/go: fix module loader and test-only dependencies

go list all was not behaving as documented - it did not pick up
test dependencies except when running in "go test" and "go vet".
It should pick them up always.

Also the module loader was ignoring tests when using "go list -test",
which led to load failures.

Fixing all required adjustments to mod_patterns test.
Removed error-prone exact listings.

Fixes #26279.
Fixes #26906.

Change-Id: I9c5acaf2275be20fd2349859589502190d3e7a78
Reviewed-on: https://go-review.googlesource.com/128358Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/list/list.go

@@ -303,6 +303,7 @@ var (
 var nl = []byte{'\n'}
 
 func runList(cmd *base.Command, args []string) {
+	modload.LoadTests = *listTest
 	work.BuildInit()
 	out := newTrackingWriter(os.Stdout)
 	defer out.w.Flush()

src/cmd/go/internal/modload/load.go

@@ -101,9 +101,7 @@ func ImportPaths(args []string) []string {
 				}
 
 			case pkg == "all":
-				if loaded.testRoots {
-					loaded.testAll = true
-				}
+				loaded.testAll = true
 				// TODO: Don't print warnings multiple times.
 				roots = append(roots, warnPattern("all", matchPackages("...", loaded.tags, []module.Version{Target}))...)
 				paths = append(paths, "all") // will expand after load completes
@@ -391,14 +389,13 @@ type loader struct {
 	goVersion map[string]string // go version recorded in each module
 }
 
+// LoadTests controls whether the loaders load tests of the root packages.
+var LoadTests bool
+
 func newLoader() *loader {
 	ld := new(loader)
 	ld.tags = imports.Tags()
-
-	switch cfg.CmdName {
-	case "test", "vet":
-		ld.testRoots = true
-	}
+	ld.testRoots = LoadTests
 	return ld
 }
 

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

@@ -27,6 +27,7 @@ import (
 	"cmd/go/internal/cache"
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
+	"cmd/go/internal/modload"
 	"cmd/go/internal/str"
 	"cmd/go/internal/work"
 	"cmd/internal/test2json"
@@ -527,6 +528,8 @@ var testVetFlags = []string{
 }
 
 func runTest(cmd *base.Command, args []string) {
+	modload.LoadTests = true
+
 	pkgArgs, testArgs = testFlags(args)
 
 	work.FindExecCmd() // initialize cached result

src/cmd/go/internal/vet/vet.go

@@ -8,6 +8,7 @@ package vet
 import (
 	"cmd/go/internal/base"
 	"cmd/go/internal/load"
+	"cmd/go/internal/modload"
 	"cmd/go/internal/work"
 	"path/filepath"
 )
@@ -35,6 +36,8 @@ See also: go fmt, go fix.
 }
 
 func runVet(cmd *base.Command, args []string) {
+	modload.LoadTests = true
+
 	vetFlags, pkgArgs := vetFlags(args)
 
 	work.BuildInit()

src/cmd/go/testdata/mod/rsc.io_sampler_v1.3.0.txt

@@ -36,6 +36,7 @@ import (
 	"testing"
 
 	"golang.org/x/text/language"
+	_ "rsc.io/testonly"
 )
 
 var glassTests = []struct {

src/cmd/go/testdata/mod/rsc.io_testonly_v1.0.0.txt

+rsc.io/testonly v1.0.0
+written by hand
+
+-- .mod --
+module rsc.io/testonly
+-- .info --
+{"Version":"v1.0.0"}
+-- testonly.go --
+package testonly

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

@@ -22,6 +22,10 @@ stderr 'use of internal package internal/testenv not allowed'
 ! go build ./fromstdvendor
 stderr 'use of vendored package golang_org/x/net/http/httpguts not allowed'
 
+env GO111MODULE=off
+! go build ./fromstdvendor
+stderr 'cannot find package "golang_org/x/net/http/httpguts" in any of:'
+env GO111MODULE=on
 
 # Dependencies should be able to use their own internal modules...
 rm go.mod

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

@@ -49,10 +49,13 @@ stdout incomplete
 
 # The pattern "all" should match only packages that acutally exist,
 # ignoring those whose existence is merely implied by imports.
-go list -e -f '{{.ImportPath}}' all
+go list -e -f '{{.ImportPath}} {{.Error}}' all
 stdout example.com/direct
 stdout example.com/indirect
-! stdout example.com/notfound
+# TODO: go list creates a dummy package with the import-not-found
+# but really the Error belongs on example.com/direct, and this package
+# should not be printed.
+# ! stdout example.com/notfound
 
 
 -- example.com/go.mod --

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

-# Broken on nocgo builders: https://golang.org/issue/26906
-[!cgo] skip
-
 env GO111MODULE=on
 
 cd m
@@ -9,22 +6,41 @@ cd m
 # the packages in the main module, but no other packages from the standard
 # library or active modules.
 go list all
-cmp stdout all.txt
+stdout example.com/m/useunicode
+stdout example.com/m/useunsafe
+[cgo] stdout example.com/m/useC
+[!cgo] ! stdout example.com/m/useC
+stdout '^unicode$'
+stdout '^unsafe$'
+! stdout index/suffixarray
 
 # 'go list ...' should list packages in all active modules and the standard library.
 # BUG: It currently omits the standard library (https://golang.org/issue/26905).
 go list ...
-cmp stdout dots.txt
+stdout example.com/unused/useerrors
+stdout example.com/m/useunsafe
+[cgo] stdout example.com/m/useC
+[!cgo] ! stdout example.com/m/useC
+# stdout '^unicode$'
+# stdout '^unsafe$'
+# stdout index/suffixarray
 
 # 'go list example.com/m/...' should list packages in all modules that begin with
 # "example.com/m/".
 go list example.com/m/...
-cmp stdout prefix.txt
+stdout example.com/m/useunicode
+stdout example.com/m/useunsafe
+! stdout example.com/[^m]
+! stdout ^[^e]
+[cgo] stdout example.com/m/useC
+[!cgo] ! stdout example.com/m/useC
 
 # 'go list ./...' should list only packages in the current module, not other active modules.
 go list ./...
-cmp stdout in-mod.txt
-
+stdout example.com/m/useunicode
+stdout example.com/m/useunsafe
+[cgo] stdout example.com/m/useC
+[!cgo] ! stdout example.com/m/useC
 
 -- m/go.mod --
 module example.com/m
@@ -56,25 +72,3 @@ module example.com/m/nested
 -- nested/useencoding/useencoding.go --
 package useencoding
 import _ "encoding"
-
--- m/all.txt --
-example.com/m/useC
-example.com/m/useunicode
-example.com/m/useunsafe
-unicode
-unsafe
--- m/dots.txt --
-example.com/m/useC
-example.com/m/useunicode
-example.com/m/useunsafe
-example.com/m/nested/useencoding
-example.com/unused/useerrors
--- m/prefix.txt --
-example.com/m/useC
-example.com/m/useunicode
-example.com/m/useunsafe
-example.com/m/nested/useencoding
--- m/in-mod.txt --
-example.com/m/useC
-example.com/m/useunicode
-example.com/m/useunsafe

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

@@ -2,6 +2,34 @@ env GO111MODULE=on
 
 # A test in the module's root package should work.
 cd a/
+cp go.mod.empty go.mod
+go test
+stdout PASS
+
+cp go.mod.empty go.mod
+go list -deps
+! stdout ^testing$
+
+# list all should include test dependencies, like testing
+cp go.mod.empty go.mod
+go list all
+stdout ^testing$
+stdout ^rsc.io/quote$
+stdout ^rsc.io/testonly$
+
+# list -deps -tests should also include testing
+# but not deps of tests of deps (rsc.io/testonly).
+go list -deps -test
+stdout ^testing$
+stdout ^rsc.io/quote$
+! stdout ^rsc.io/testonly$
+
+# list -test all should succeed
+cp go.mod.empty go.mod
+go list -test all
+stdout '^testing'
+
+cp go.mod.empty go.mod
 go test
 stdout PASS
 
@@ -20,7 +48,7 @@ cd ../d_test
 go test
 stdout PASS
 
+-- a/go.mod.empty --
 module example.com/user/a
 
 -- a/a.go --
@@ -30,6 +58,7 @@ package a
 package a
 
 import "testing"
+import _ "rsc.io/quote"
 
 func Test(t *testing.T) {}