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>

2 files changed, 120 insertions, 8 deletions

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()