cmd/dist,internal/testdir: more cooperative host test mechanism

On cross-compiling builder machines, we run internal/testdir on the
host, where it can access the Go toolchain to build binaries for the
guest and run them through an exec wrapper. Currently this uses dist
test's existing host test mechanism, which is quite complicated and we
are planning to eliminate (#59999).

Switch internal/testdir to use a more cooperative mechanism. With this
CL, dist still understands that it has to build and run the test using
the host GOOS/GOARCH, but rather than doing complicated manipulation
of environment variables itself, it passes the guest GOOS/GOARCH to
the test, which can easily inject it into its environment. This means
dist test can use "go test" directly, rather than having to split up
the build and run steps.

For #37486.

Change-Id: I556938c0b641960bb778b88b13f2b26256edc7c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/492985
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 26 insertions, 9 deletions

diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index 5a47b86bc6..bce1c7ccfd 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -301,6 +301,8 @@ type goTest struct {
 	dir string   // If non-empty, run in GOROOT/src-relative directory dir
 	env []string // Environment variables to add, as KEY=VAL. KEY= unsets a variable
 
+	runOnHost bool // When cross-compiling, run this test on the host instead of guest
+
 	// We have both pkg and pkgs as a convenience. Both may be set, in which
 	// case they will be combined. If both are empty, the default is ".".
 	pkgs []string // Multiple packages to test
@@ -312,7 +314,7 @@ type goTest struct {
 // bgCommand returns a go test Cmd. The result has Stdout and Stderr set to nil
 // and is intended to be added to the work queue.
 func (opts *goTest) bgCommand(t *tester) *exec.Cmd {
-	goCmd, build, run, pkgs, setupCmd := opts.buildArgs(t)
+	goCmd, build, run, pkgs, testFlags, setupCmd := opts.buildArgs(t)
 
 	// Combine the flags.
 	args := append([]string{"test"}, build...)
@@ -323,7 +325,7 @@ func (opts *goTest) bgCommand(t *tester) *exec.Cmd {
 	}
 	args = append(args, pkgs...)
 	if !t.compileOnly {
-		args = append(args, opts.testFlags...)
+		args = append(args, testFlags...)
 	}
 
 	cmd := exec.Command(goCmd, args...)
@@ -352,7 +354,7 @@ func (opts *goTest) run(t *tester) error {
 // the host, but its resulting binaries will be run through a go_exec wrapper
 // that runs them on the target.
 func (opts *goTest) runHostTest(t *tester) error {
-	goCmd, build, run, pkgs, setupCmd := opts.buildArgs(t)
+	goCmd, build, run, pkgs, testFlags, setupCmd := opts.buildArgs(t)
 
 	// Build the host test binary
 	if len(pkgs) != 1 {
@@ -400,7 +402,7 @@ func (opts *goTest) runHostTest(t *tester) error {
 	}
 
 	// Run the test
-	args = append(run, opts.testFlags...)
+	args = append(run, testFlags...)
 	cmd = exec.Command(bin, args...)
 	setupCmd(cmd)
 	cmd.Stdout = os.Stdout
@@ -414,11 +416,12 @@ func (opts *goTest) runHostTest(t *tester) error {
 // buildArgs is in internal helper for goTest that constructs the elements of
 // the "go test" command line. goCmd is the path to the go command to use. build
 // is the flags for building the test. run is the flags for running the test.
-// pkgs is the list of packages to build and run.
+// pkgs is the list of packages to build and run. testFlags is the list of flags
+// to pass to the test package.
 //
-// The caller is responsible for adding opts.testFlags, and must call setupCmd
-// on the resulting exec.Cmd to set its directory and environment.
-func (opts *goTest) buildArgs(t *tester) (goCmd string, build, run, pkgs []string, setupCmd func(*exec.Cmd)) {
+// The caller must call setupCmd on the resulting exec.Cmd to set its directory
+// and environment.
+func (opts *goTest) buildArgs(t *tester) (goCmd string, build, run, pkgs, testFlags []string, setupCmd func(*exec.Cmd)) {
 	goCmd = gorootBinGo
 	if opts.goroot != "" {
 		goCmd = filepath.Join(opts.goroot, "bin", "go")
@@ -482,6 +485,16 @@ func (opts *goTest) buildArgs(t *tester) (goCmd string, build, run, pkgs []strin
 		pkgs = []string{"."}
 	}
 
+	runOnHost := opts.runOnHost && (goarch != gohostarch || goos != gohostos)
+	needTestFlags := len(opts.testFlags) > 0 || runOnHost
+	if needTestFlags {
+		testFlags = append([]string{"-args"}, opts.testFlags...)
+	}
+	if runOnHost {
+		// -target is a special flag understood by tests that can run on the host
+		testFlags = append(testFlags, "-target="+goos+"/"+goarch)
+	}
+
 	thisGoroot := goroot
 	if opts.goroot != "" {
 		thisGoroot = opts.goroot
@@ -506,6 +519,10 @@ func (opts *goTest) buildArgs(t *tester) (goCmd string, build, run, pkgs []strin
 				}
 			}
 		}
+		if runOnHost {
+			setEnv(cmd, "GOARCH", gohostarch)
+			setEnv(cmd, "GOOS", gohostos)
+		}
 	}
 
 	return
@@ -929,8 +946,8 @@ func (t *tester) registerTests() {
 				&goTest{
 					dir:       "internal/testdir",
 					testFlags: []string{fmt.Sprintf("-shard=%d", shard), fmt.Sprintf("-shards=%d", nShards)},
+					runOnHost: true,
 				},
-				rtHostTest{},
 			)
 		}
 	}