cmd/go/internal: use sync.OnceFunc, sync.OnceValue

Cleaner code, less global variables Change-Id: I6d842932e538849260b36fa408bc5ddae68c05ab Reviewed-on: https://go-review.googlesource.com/c/go/+/611018 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Auto-Submit: Ian Lance Taylor <iant@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
aytanet · Sep 6, 2024 · d1ce116 · d1ce116
1 parent 4777fd3
commit d1ce116
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Showing 5 changed files with 21 additions and 39 deletions.
diff --git a/src/cmd/go/internal/base/path.go b/src/cmd/go/internal/base/path.go
@@ -15,9 +15,6 @@ import (
 	"cmd/go/internal/str"
 )
 
-var cwd string
-var cwdOnce sync.Once
-
 // UncachedCwd returns the current working directory.
 // Most callers should use Cwd, which caches the result for future use.
 // UncachedCwd is appropriate to call early in program startup before flag parsing,
@@ -30,12 +27,11 @@ func UncachedCwd() string {
 	return wd
 }
 
+var cwdOnce = sync.OnceValue(UncachedCwd)
+
 // Cwd returns the current working directory at the time of the first call.
 func Cwd() string {
-	cwdOnce.Do(func() {
-		cwd = UncachedCwd()
-	})
-	return cwd
+	return cwdOnce()
 }
 
 // ShortPath returns an absolute or relative name for path, whatever is shorter.

diff --git a/src/cmd/go/internal/base/signal.go b/src/cmd/go/internal/base/signal.go
@@ -23,9 +23,9 @@ func processSignals() {
 	}()
 }
 
-var onceProcessSignals sync.Once
+var processSignalsOnce = sync.OnceFunc(processSignals)
 
 // StartSigHandlers starts the signal handlers.
 func StartSigHandlers() {
-	onceProcessSignals.Do(processSignals)
+	processSignalsOnce()
 }
diff --git a/src/cmd/go/internal/cache/default.go b/src/cmd/go/internal/cache/default.go
@@ -18,14 +18,10 @@ import (
 // Default returns the default cache to use.
 // It never returns nil.
 func Default() Cache {
-	defaultOnce.Do(initDefaultCache)
-	return defaultCache
+	return initDefaultCacheOnce()
 }
 
-var (
-	defaultOnce  sync.Once
-	defaultCache Cache
-)
+var initDefaultCacheOnce = sync.OnceValue(initDefaultCache)
 
 // cacheREADME is a message stored in a README in the cache directory.
 // Because the cache lives outside the normal Go trees, we leave the
@@ -38,7 +34,7 @@ See golang.org to learn more about Go.
 
 // initDefaultCache does the work of finding the default cache
 // the first time Default is called.
-func initDefaultCache() {
+func initDefaultCache() Cache {
 	dir, _ := DefaultDir()
 	if dir == "off" {
 		if defaultDirErr != nil {
@@ -60,10 +56,10 @@ func initDefaultCache() {
 	}
 
 	if v := cfg.Getenv("GOCACHEPROG"); v != "" && goexperiment.CacheProg {
-		defaultCache = startCacheProg(v, diskCache)
-	} else {
-		defaultCache = diskCache
+		return startCacheProg(v, diskCache)
 	}
+
+	return diskCache
 }
 
 var (

diff --git a/src/cmd/go/internal/imports/tags.go b/src/cmd/go/internal/imports/tags.go
@@ -9,21 +9,15 @@ import (
 	"sync"
 )
 
-var (
-	tags     map[string]bool
-	tagsOnce sync.Once
-)
-
 // Tags returns a set of build tags that are true for the target platform.
 // It includes GOOS, GOARCH, the compiler, possibly "cgo",
 // release tags like "go1.13", and user-specified build tags.
 func Tags() map[string]bool {
-	tagsOnce.Do(func() {
-		tags = loadTags()
-	})
-	return tags
+	return loadTagsOnce()
 }
 
+var loadTagsOnce = sync.OnceValue(loadTags)
+
 func loadTags() map[string]bool {
 	tags := map[string]bool{
 		cfg.BuildContext.GOOS:     true,
@@ -45,17 +39,13 @@ func loadTags() map[string]bool {
 	return tags
 }
 
-var (
-	anyTags     map[string]bool
-	anyTagsOnce sync.Once
-)
-
 // AnyTags returns a special set of build tags that satisfy nearly all
 // build tag expressions. Only "ignore" and malformed build tag requirements
 // are considered false.
 func AnyTags() map[string]bool {
-	anyTagsOnce.Do(func() {
-		anyTags = map[string]bool{"*": true}
-	})
-	return anyTags
+	return anyTagsOnce()
 }
+
+var anyTagsOnce = sync.OnceValue(func() map[string]bool {
+	return map[string]bool{"*": true}
+})
diff --git a/src/cmd/go/internal/work/buildid.go b/src/cmd/go/internal/work/buildid.go
@@ -410,8 +410,8 @@ var (
 	counterCacheHit  = counter.New("go/buildcache/hit")
 	counterCacheMiss = counter.New("go/buildcache/miss")
 
-	onceIncStdlibRecompiled sync.Once
 	stdlibRecompiled        = counter.New("go/buildcache/stdlib-recompiled")
+	stdlibRecompiledIncOnce = sync.OnceFunc(stdlibRecompiled.Inc)
 )
 
 // useCache tries to satisfy the action a, which has action ID actionHash,
@@ -467,7 +467,7 @@ func (b *Builder) useCache(a *Action, actionHash cache.ActionID, target string,
 			counterCacheHit.Inc()
 		} else {
 			if a.Package != nil && a.Package.Standard {
-				onceIncStdlibRecompiled.Do(stdlibRecompiled.Inc)
+				stdlibRecompiledIncOnce()
 			}
 			counterCacheMiss.Inc()
 		}