cmd/internal/script: new hook for adding in toolchain script conditions

Introduce a new function AddToolChainScriptConditions that augments a
default "script.Cond" set with a collection of useful conditions,
including godebug/goexperiment, cgo, race support, buildmode, asan,
msan, and so on. Having these conditions available makes it easier to
write script tests that deal with specific build-flavor corner cases.
The functions backing the new conditions are helper functions migrated
over from the Go command's script test setup.

Updates #68606.

Change-Id: I14def1115b54dc47529c983abcd2c5ea9326b9de
Reviewed-on: https://go-review.googlesource.com/c/go/+/601715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

5 files changed, 126 insertions, 93 deletions

diff --git a/src/cmd/compile/testdata/script/script_test_basics.txt b/src/cmd/compile/testdata/script/script_test_basics.txt
index ecc28951a1..7fe99dbbc2 100644
--- a/src/cmd/compile/testdata/script/script_test_basics.txt
+++ b/src/cmd/compile/testdata/script/script_test_basics.txt
@@ -4,6 +4,7 @@
 go build
 [!cgo] skip
 cc -c testdata/mumble.c
+[GOEXPERIMENT:fieldtrack] help exec
 
 -- go.mod --
 module main
diff --git a/src/cmd/go/script_test.go b/src/cmd/go/script_test.go
index 36605bb66c..09232100f5 100644
--- a/src/cmd/go/script_test.go
+++ b/src/cmd/go/script_test.go
@@ -89,7 +89,7 @@ func TestScript(t *testing.T) {
 		t.Fatal(err)
 	}
 	engine := &script.Engine{
-		Conds: scriptConditions(),
+		Conds: scriptConditions(t),
 		Cmds:  scriptCommands(quitSignal(), gracePeriod),
 		Quiet: !testing.Verbose(),
 	}
diff --git a/src/cmd/go/scriptconds_test.go b/src/cmd/go/scriptconds_test.go
index b4f139a983..262214f6a9 100644
--- a/src/cmd/go/scriptconds_test.go
+++ b/src/cmd/go/scriptconds_test.go
@@ -10,21 +10,21 @@ import (
 	"cmd/internal/script/scripttest"
 	"errors"
 	"fmt"
-	"internal/buildcfg"
-	"internal/platform"
 	"internal/testenv"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"runtime/debug"
-	"strings"
 	"sync"
+	"testing"
 )
 
-func scriptConditions() map[string]script.Cond {
+func scriptConditions(t *testing.T) map[string]script.Cond {
 	conds := scripttest.DefaultConds()
 
+	scripttest.AddToolChainScriptConditions(t, conds, goHostOS, goHostArch)
+
 	add := func(name string, cond script.Cond) {
 		if _, ok := conds[name]; ok {
 			panic(fmt.Sprintf("condition %q is already registered", name))
@@ -37,26 +37,10 @@ func scriptConditions() map[string]script.Cond {
 	}
 
 	add("abscc", script.Condition("default $CC path is absolute and exists", defaultCCIsAbsolute))
-	add("asan", sysCondition("-asan", platform.ASanSupported, true))
-	add("buildmode", script.PrefixCondition("go supports -buildmode=<suffix>", hasBuildmode))
 	add("case-sensitive", script.OnceCondition("$WORK filesystem is case-sensitive", isCaseSensitive))
 	add("cc", script.PrefixCondition("go env CC = <suffix> (ignoring the go/env file)", ccIs))
-	add("cgo", script.BoolCondition("host CGO_ENABLED", testenv.HasCGO()))
-	add("cgolinkext", script.Condition("platform requires external linking for cgo", cgoLinkExt))
-	add("cross", script.BoolCondition("cmd/go GOOS/GOARCH != GOHOSTOS/GOHOSTARCH", goHostOS != runtime.GOOS || goHostArch != runtime.GOARCH))
-	add("fuzz", sysCondition("-fuzz", platform.FuzzSupported, false))
-	add("fuzz-instrumented", sysCondition("-fuzz with instrumentation", platform.FuzzInstrumented, false))
 	add("git", lazyBool("the 'git' executable exists and provides the standard CLI", hasWorkingGit))
-	add("GODEBUG", script.PrefixCondition("GODEBUG contains <suffix>", hasGodebug))
-	add("GOEXPERIMENT", script.PrefixCondition("GOEXPERIMENT <suffix> is enabled", hasGoexperiment))
-	add("go-builder", script.BoolCondition("GO_BUILDER_NAME is non-empty", testenv.Builder() != ""))
-	add("link", lazyBool("testenv.HasLink()", testenv.HasLink))
-	add("msan", sysCondition("-msan", platform.MSanSupported, true))
-	add("mustlinkext", script.Condition("platform always requires external linking", mustLinkExt))
 	add("net", script.PrefixCondition("can connect to external network host <suffix>", hasNet))
-	add("pielinkext", script.Condition("platform requires external linking for PIE", pieLinkExt))
-	add("race", sysCondition("-race", platform.RaceDetectorSupported, true))
-	add("symlink", lazyBool("testenv.HasSymlink()", testenv.HasSymlink))
 	add("trimpath", script.OnceCondition("test binary was built with -trimpath", isTrimpath))
 
 	return conds
@@ -84,23 +68,6 @@ func ccIs(s *script.State, want string) (bool, error) {
 	return cfg.DefaultCC(GOOS, GOARCH) == want, nil
 }
 
-func sysCondition(flag string, f func(goos, goarch string) bool, needsCgo bool) script.Cond {
-	return script.Condition(
-		"GOOS/GOARCH supports "+flag,
-		func(s *script.State) (bool, error) {
-			GOOS, _ := s.LookupEnv("GOOS")
-			GOARCH, _ := s.LookupEnv("GOARCH")
-			cross := goHostOS != GOOS || goHostArch != GOARCH
-			return (!needsCgo || (testenv.HasCGO() && !cross)) && f(GOOS, GOARCH), nil
-		})
-}
-
-func hasBuildmode(s *script.State, mode string) (bool, error) {
-	GOOS, _ := s.LookupEnv("GOOS")
-	GOARCH, _ := s.LookupEnv("GOARCH")
-	return platform.BuildModeSupported(runtime.Compiler, mode, GOOS, GOARCH), nil
-}
-
 var scriptNetEnabled sync.Map // testing.TB → already enabled
 
 func hasNet(s *script.State, host string) (bool, error) {
@@ -137,35 +104,6 @@ func hasNet(s *script.State, host string) (bool, error) {
 	return true, nil
 }
 
-func hasGodebug(s *script.State, value string) (bool, error) {
-	godebug, _ := s.LookupEnv("GODEBUG")
-	for _, p := range strings.Split(godebug, ",") {
-		if strings.TrimSpace(p) == value {
-			return true, nil
-		}
-	}
-	return false, nil
-}
-
-func hasGoexperiment(s *script.State, value string) (bool, error) {
-	GOOS, _ := s.LookupEnv("GOOS")
-	GOARCH, _ := s.LookupEnv("GOARCH")
-	goexp, _ := s.LookupEnv("GOEXPERIMENT")
-	flags, err := buildcfg.ParseGOEXPERIMENT(GOOS, GOARCH, goexp)
-	if err != nil {
-		return false, err
-	}
-	for _, exp := range flags.All() {
-		if value == exp {
-			return true, nil
-		}
-		if strings.TrimPrefix(value, "no") == strings.TrimPrefix(exp, "no") {
-			return false, nil
-		}
-	}
-	return false, fmt.Errorf("unrecognized GOEXPERIMENT %q", value)
-}
-
 func isCaseSensitive() (bool, error) {
 	tmpdir, err := os.MkdirTemp(testTmpDir, "case-sensitive")
 	if err != nil {
@@ -213,21 +151,3 @@ func hasWorkingGit() bool {
 	_, err := exec.LookPath("git")
 	return err == nil
 }
-
-func cgoLinkExt(s *script.State) (bool, error) {
-	GOOS, _ := s.LookupEnv("GOOS")
-	GOARCH, _ := s.LookupEnv("GOARCH")
-	return platform.MustLinkExternal(GOOS, GOARCH, true), nil
-}
-
-func mustLinkExt(s *script.State) (bool, error) {
-	GOOS, _ := s.LookupEnv("GOOS")
-	GOARCH, _ := s.LookupEnv("GOARCH")
-	return platform.MustLinkExternal(GOOS, GOARCH, false), nil
-}
-
-func pieLinkExt(s *script.State) (bool, error) {
-	GOOS, _ := s.LookupEnv("GOOS")
-	GOARCH, _ := s.LookupEnv("GOARCH")
-	return !platform.InternalLinkPIESupported(GOOS, GOARCH), nil
-}
diff --git a/src/cmd/internal/script/scripttest/conditions.go b/src/cmd/internal/script/scripttest/conditions.go
new file mode 100644
index 0000000000..66dbfc2ac6
--- /dev/null
+++ b/src/cmd/internal/script/scripttest/conditions.go
@@ -0,0 +1,116 @@
+// Copyright 2024 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 scripttest
+
+import (
+	"cmd/internal/script"
+	"fmt"
+	"internal/buildcfg"
+	"internal/platform"
+	"internal/testenv"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+// AddToolChainConditions accepts a script.Cond map and adds into it a
+// set of commonly used conditions for doing toolchains testing,
+// including whether the platform supports cgo, a buildmode condition,
+// support for GOEXPERIMENT testing, etc. Callers must also pass in
+// current GOHOSTOOS/GOHOSTARCH settings, since some of the conditions
+// introduced can be influenced by them.
+func AddToolChainScriptConditions(t *testing.T, conds map[string]script.Cond, goHostOS, goHostArch string) {
+	add := func(name string, cond script.Cond) {
+		if _, ok := conds[name]; ok {
+			t.Fatalf("condition %q is already registered", name)
+		}
+		conds[name] = cond
+	}
+
+	lazyBool := func(summary string, f func() bool) script.Cond {
+		return script.OnceCondition(summary, func() (bool, error) { return f(), nil })
+	}
+
+	add("asan", sysCondition("-asan", platform.ASanSupported, true, goHostOS, goHostArch))
+	add("buildmode", script.PrefixCondition("go supports -buildmode=<suffix>", hasBuildmode))
+	add("cgo", script.BoolCondition("host CGO_ENABLED", testenv.HasCGO()))
+	add("cgolinkext", script.Condition("platform requires external linking for cgo", cgoLinkExt))
+	add("cross", script.BoolCondition("cmd/go GOOS/GOARCH != GOHOSTOS/GOHOSTARCH", goHostOS != runtime.GOOS || goHostArch != runtime.GOARCH))
+	add("fuzz", sysCondition("-fuzz", platform.FuzzSupported, false, goHostOS, goHostArch))
+	add("fuzz-instrumented", sysCondition("-fuzz with instrumentation", platform.FuzzInstrumented, false, goHostOS, goHostArch))
+	add("GODEBUG", script.PrefixCondition("GODEBUG contains <suffix>", hasGodebug))
+	add("GOEXPERIMENT", script.PrefixCondition("GOEXPERIMENT <suffix> is enabled", hasGoexperiment))
+	add("go-builder", script.BoolCondition("GO_BUILDER_NAME is non-empty", testenv.Builder() != ""))
+	add("link", lazyBool("testenv.HasLink()", testenv.HasLink))
+	add("msan", sysCondition("-msan", platform.MSanSupported, true, goHostOS, goHostArch))
+	add("mustlinkext", script.Condition("platform always requires external linking", mustLinkExt))
+	add("pielinkext", script.Condition("platform requires external linking for PIE", pieLinkExt))
+	add("race", sysCondition("-race", platform.RaceDetectorSupported, true, goHostOS, goHostArch))
+	add("symlink", lazyBool("testenv.HasSymlink()", testenv.HasSymlink))
+}
+
+func sysCondition(flag string, f func(goos, goarch string) bool, needsCgo bool, goHostOS, goHostArch string) script.Cond {
+	return script.Condition(
+		"GOOS/GOARCH supports "+flag,
+		func(s *script.State) (bool, error) {
+			GOOS, _ := s.LookupEnv("GOOS")
+			GOARCH, _ := s.LookupEnv("GOARCH")
+			cross := goHostOS != GOOS || goHostArch != GOARCH
+			return (!needsCgo || (testenv.HasCGO() && !cross)) && f(GOOS, GOARCH), nil
+		})
+}
+
+func hasBuildmode(s *script.State, mode string) (bool, error) {
+	GOOS, _ := s.LookupEnv("GOOS")
+	GOARCH, _ := s.LookupEnv("GOARCH")
+	return platform.BuildModeSupported(runtime.Compiler, mode, GOOS, GOARCH), nil
+}
+
+func cgoLinkExt(s *script.State) (bool, error) {
+	GOOS, _ := s.LookupEnv("GOOS")
+	GOARCH, _ := s.LookupEnv("GOARCH")
+	return platform.MustLinkExternal(GOOS, GOARCH, true), nil
+}
+
+func mustLinkExt(s *script.State) (bool, error) {
+	GOOS, _ := s.LookupEnv("GOOS")
+	GOARCH, _ := s.LookupEnv("GOARCH")
+	return platform.MustLinkExternal(GOOS, GOARCH, false), nil
+}
+
+func pieLinkExt(s *script.State) (bool, error) {
+	GOOS, _ := s.LookupEnv("GOOS")
+	GOARCH, _ := s.LookupEnv("GOARCH")
+	return !platform.InternalLinkPIESupported(GOOS, GOARCH), nil
+}
+
+func hasGodebug(s *script.State, value string) (bool, error) {
+	godebug, _ := s.LookupEnv("GODEBUG")
+	for _, p := range strings.Split(godebug, ",") {
+		if strings.TrimSpace(p) == value {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+func hasGoexperiment(s *script.State, value string) (bool, error) {
+	GOOS, _ := s.LookupEnv("GOOS")
+	GOARCH, _ := s.LookupEnv("GOARCH")
+	goexp, _ := s.LookupEnv("GOEXPERIMENT")
+	flags, err := buildcfg.ParseGOEXPERIMENT(GOOS, GOARCH, goexp)
+	if err != nil {
+		return false, err
+	}
+	for _, exp := range flags.All() {
+		if value == exp {
+			return true, nil
+		}
+		if strings.TrimPrefix(value, "no") == strings.TrimPrefix(exp, "no") {
+			return false, nil
+		}
+	}
+	return false, fmt.Errorf("unrecognized GOEXPERIMENT %q", value)
+}
diff --git a/src/cmd/internal/script/scripttest/run.go b/src/cmd/internal/script/scripttest/run.go
index d2f3ed8ca9..29eb6f88f2 100644
--- a/src/cmd/internal/script/scripttest/run.go
+++ b/src/cmd/internal/script/scripttest/run.go
@@ -71,13 +71,6 @@ func RunToolScriptTest(t *testing.T, repls []ToolReplacement, pattern string) {
 		cmds[name] = cmd
 	}
 
-	addcond := func(name string, cond script.Cond) {
-		if _, ok := conds[name]; ok {
-			panic(fmt.Sprintf("condition %q is already registered", name))
-		}
-		conds[name] = cond
-	}
-
 	prependToPath := func(env []string, dir string) {
 		found := false
 		for k := range env {
@@ -135,7 +128,10 @@ func RunToolScriptTest(t *testing.T, repls []ToolReplacement, pattern string) {
 	cccmd := script.Program(goEnv("CC"), interrupt, gracePeriod)
 	addcmd("go", gocmd)
 	addcmd("cc", cccmd)
-	addcond("cgo", script.BoolCondition("host CGO_ENABLED", testenv.HasCGO()))
+
+	// Add various helpful conditions related to builds and toolchain use.
+	goHostOS, goHostArch := goEnv("GOHOSTOS"), goEnv("GOHOSTARCH")
+	AddToolChainScriptConditions(t, conds, goHostOS, goHostArch)
 
 	// Environment setup.
 	env := os.Environ()