cmd/go: consolidate TestInstalls into gopath_install script test

TestInstalls was already mostly redundant with
TestInstallInto{GOPATH,GOBIN}, except for one additional check for the
install location of cmd/fix.

We can't assume that GOROOT is writable in general, so we also can't
assume that the test will be able to reinstall cmd/fix at run time.
Moreover, other processes running in parallel may expect to invoke
cmd/fix themselves, so this test temporarily removing it could induce
systemwide flakes.

We could carefully construct a parallel GOROOT and install cmd/fix
into it, but we can get *almost* as much coverage — at a much lower
cost — by checking the output of 'go list' instead of actually
rebuilding and reinstalling the binary.

Updates #28387
Updates #30316

Change-Id: Id49f44a68b0c52dfabb84c665f63c4e7db58dd49
Reviewed-on: https://go-review.googlesource.com/c/go/+/207965
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/go_test.go

@@ -1376,48 +1376,6 @@ func TestGoGetTestOnlyPkg(t *testing.T) {
 	tg.run("get", "-t", "golang.org/x/tour/content...")
 }
 
-func TestInstalls(t *testing.T) {
-	if testing.Short() {
-		t.Skip("don't install into GOROOT in short mode")
-	}
-
-	tg := testgo(t)
-	defer tg.cleanup()
-	tg.parallel()
-	tg.tempDir("gobin")
-	tg.setenv("GOPATH", tg.path("."))
-	goroot := runtime.GOROOT()
-	tg.setenv("GOROOT", goroot)
-
-	// cmd/fix installs into tool
-	tg.run("env", "GOOS")
-	goos := strings.TrimSpace(tg.getStdout())
-	tg.setenv("GOOS", goos)
-	tg.run("env", "GOARCH")
-	goarch := strings.TrimSpace(tg.getStdout())
-	tg.setenv("GOARCH", goarch)
-	fixbin := filepath.Join(goroot, "pkg", "tool", goos+"_"+goarch, "fix") + exeSuffix
-	tg.must(robustio.RemoveAll(fixbin))
-	tg.run("install", "cmd/fix")
-	tg.wantExecutable(fixbin, "did not install cmd/fix to $GOROOT/pkg/tool")
-	tg.must(os.Remove(fixbin))
-	tg.setenv("GOBIN", tg.path("gobin"))
-	tg.run("install", "cmd/fix")
-	tg.wantExecutable(fixbin, "did not install cmd/fix to $GOROOT/pkg/tool with $GOBIN set")
-	tg.unsetenv("GOBIN")
-
-	// gopath program installs into GOBIN
-	tg.tempFile("src/progname/p.go", `package main; func main() {}`)
-	tg.setenv("GOBIN", tg.path("gobin"))
-	tg.run("install", "progname")
-	tg.unsetenv("GOBIN")
-	tg.wantExecutable(tg.path("gobin/progname")+exeSuffix, "did not install progname to $GOBIN/progname")
-
-	// gopath program installs into GOPATH/bin
-	tg.run("install", "progname")
-	tg.wantExecutable(tg.path("bin/progname")+exeSuffix, "did not install progname to $GOPATH/bin/progname")
-}
-
 // Issue 4104.
 func TestGoTestWithPackageListedMultipleTimes(t *testing.T) {
 	tooSlow(t)

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

@@ -33,6 +33,17 @@ env GOBIN=$WORK/bin1
 go install go-cmd-test/helloworld.go
 exists $GOBIN/helloworld$GOEXE
 
+# We can't assume that we can write to GOROOT, because it may not be writable.
+# However, we can check its install location using 'go list'.
+# cmd/fix should be installed to GOROOT/pkg, not GOPATH/bin.
+env GOPATH=$PWD
+go list -f '{{.Target}}' cmd/fix
+stdout $GOROOT'[/\\]pkg[/\\]tool[/\\]'$GOOS'_'$GOARCH'[/\\]fix'$GOEXE'$'
+
+# GOBIN should not affect toolchain install locations.
+env GOBIN=$WORK/bin1
+go list -f '{{.Target}}' cmd/fix
+stdout $GOROOT'[/\\]pkg[/\\]tool[/\\]'$GOOS'_'$GOARCH'[/\\]fix'$GOEXE'$'
 
 -- go-cmd-test/helloworld.go --
 package main