version: undo previous "optimization", do more work lazily

Commit 59c254579ea63c669ffb3b5031e51288422c5194 moved a lot of work
from functions that could be eliminated at compile time (because
tests against runtime.GOOS are compile-time constant), into code
that must always run before main().

So, revert that, and instead optimize the package only by moving the
remaining string processing code behind sync.Onces.

Signed-off-by: David Anderson <danderson@tailscale.com>

version/prop.go

@@ -4,34 +4,126 @@
 package version
 
 import (
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
 	"strings"
+	"sync"
 
 	"tailscale.com/tailcfg"
 )
 
 // IsMobile reports whether this is a mobile client build.
-func IsMobile() bool { return isMobile }
+func IsMobile() bool {
+	return runtime.GOOS == "android" || runtime.GOOS == "ios"
+}
 
-// OS returns runtime.GOOS, except instead of returning "darwin" it
+// OS returns runtime.GOOS, except instead of returning "darwin" it returns
-// returns "iOS" or "macOS".
+// "iOS" or "macOS".
-func OS() string { return legacyOS }
+func OS() string {
+	// If you're wondering why we have this function that just returns
+	// runtime.GOOS written differently: in the old days, Go reported
+	// GOOS=darwin for both iOS and macOS, so we needed this function to
+	// differentiate them. Then a later Go release added GOOS=ios as a separate
+	// platform, but by then the "iOS" and "macOS" values we'd picked, with that
+	// exact capitalization, were already baked into databases.
+	if runtime.GOOS == "ios" {
+		return "iOS"
+	}
+	if runtime.GOOS == "darwin" {
+		return "macOS"
+	}
+	return runtime.GOOS
+}
+
+var (
+	macFlavorOnce  sync.Once
+	isMacSysExt    bool
+	isMacSandboxed bool
+)
+
+func initMacFlavor() {
+	exe, err := os.Executable()
+	if err != nil {
+		return
+	}
+	isMacSysExt = filepath.Base(exe) == "io.tailscale.ipn.macsys.network-extension"
+	isMacSandboxed = isMacSysExt || strings.HasSuffix(exe, "/Contents/MacOS/Tailscale") || strings.HasSuffix(exe, "/Contents/MacOS/IPNExtension")
+}
 
 // IsSandboxedMacOS reports whether this process is a sandboxed macOS
 // process (either the app or the extension). It is true for the Mac App Store
 // and macsys (System Extension) version on macOS, and false for
 // tailscaled-on-macOS.
-func IsSandboxedMacOS() bool { return isSandboxedMacOS }
+func IsSandboxedMacOS() bool {
+	if runtime.GOOS != "darwin" {
+		return false
+	}
+	macFlavorOnce.Do(initMacFlavor)
+	return isMacSandboxed
+}
 
 // IsMacSysExt whether this binary is from the standalone "System
 // Extension" (a.k.a. "macsys") version of Tailscale for macOS.
-func IsMacSysExt() bool { return isMacSysExt }
+func IsMacSysExt() bool {
+	if runtime.GOOS != "darwin" {
+		return false
+	}
+	macFlavorOnce.Do(initMacFlavor)
+	return isMacSysExt
+}
+
+var (
+	winFlavorOnce sync.Once
+	isWindowsGUI  bool
+)
+
+func initWinFlavor() {
+	exe, err := os.Executable()
+	if err != nil {
+		return
+	}
+	isWindowsGUI = strings.EqualFold(exe, "tailscale-ipn.exe") || strings.EqualFold(exe, "tailscale-ipn")
+}
 
 // IsWindowsGUI reports whether the current process is the Windows GUI.
-func IsWindowsGUI() bool { return isWindowsGUI }
+func IsWindowsGUI() bool {
+	if runtime.GOOS != "windows" {
+		return false
+	}
+	exe, _ := os.Executable()
+	exe = filepath.Base(exe)
+	return strings.EqualFold(exe, "tailscale-ipn.exe") || strings.EqualFold(exe, "tailscale-ipn")
+}
+
+var (
+	isUnstableOnce  sync.Once
+	isUnstableBuild bool
+)
 
 // IsUnstableBuild reports whether this is an unstable build.
 // That is, whether its minor version number is odd.
-func IsUnstableBuild() bool { return isUnstable }
+func IsUnstableBuild() bool {
+	isUnstableOnce.Do(initUnstable)
+	return isUnstableBuild
+}
+
+func initUnstable() {
+	_, rest, ok := strings.Cut(Short, ".")
+	if !ok {
+		return
+	}
+	minorStr, _, ok := strings.Cut(rest, ".")
+	if !ok {
+		return
+	}
+	minor, err := strconv.Atoi(minorStr)
+	if err != nil {
+		return
+	}
+	isUnstableBuild = minor%2 == 1
+}
 
 // Meta is a JSON-serializable type that contains all the version
 // information.

version/version.go

@@ -5,93 +5,29 @@
 package version
 
 import (
-	"os"
-	"path/filepath"
-	"runtime"
 	"runtime/debug"
-	"strconv"
 	"strings"
 
 	tailscaleroot "tailscale.com"
 )
 
-var (
+// Long is a full version number for this build, of the form
-	// Long is a full version number for this build, of the form
+// "x.y.z-commithash" for builds stamped in the usual way (see
-	// "x.y.z-commithash" for builds stamped in the usual way (see build_dist.sh
+// build_dist.sh in the root) or, for binaries built by hand with the
-	// in the root) or, for binaries built by hand with the go tool, it's of the
+// go tool, it's of the form "1.23.0-dev20220316-t29837428937{,-dirty}"
-	// form "1.23.0-dev20220316-t29837428937{,-dirty}" where "1.23.0" comes from
+// where "1.23.0" comes from ../VERSION.txt and the part after dev
-	// ../VERSION.txt and the part after dev is YYYYMMDD of the commit time, and
+// is YYYYMMDD of the commit time, and the part after -t is the commit
-	// the part after -t is the commit hash. The dirty suffix is whether there
+// hash. The dirty suffix is whether there are uncommitted changes.
-	// are uncommitted changes.
+var Long = ""
-	Long string
 
-	// Short is a short version number for this build, of the form
+// Short is a short version number for this build, of the form
-	// "x.y.z" for builds stamped in the usual way (see
+// "x.y.z" for builds stamped in the usual way (see
-	// build_dist.sh in the root) or, for binaries built by hand with the
+// build_dist.sh in the root) or, for binaries built by hand with the
-	// go tool, it's like Long's dev form, but ending at the date part,
+// go tool, it's like Long's dev form, but ending at the date part,
-	// of the form "1.23.0-dev20220316".
+// of the form "1.23.0-dev20220316".
-	Short string
+var Short = ""
-
-	// GitCommit, if non-empty, is the git commit of the
-	// github.com/tailscale/tailscale repository at which Tailscale was
-	// built. Its format is the one returned by `git describe --always
-	// --exclude "*" --dirty --abbrev=200`.
-	GitCommit string
-
-	// GitDirty is whether Go stamped the binary as having dirty version
-	// control changes in the working directory (debug.ReadBuildInfo
-	// setting "vcs.modified" was true).
-	GitDirty bool
-
-	// ExtraGitCommit, if non-empty, is the git commit of a "supplemental"
-	// repository at which Tailscale was built. Its format is the same as
-	// gitCommit.
-	//
-	// ExtraGitCommit is used to track the source revision when the main
-	// Tailscale repository is integrated into and built from another
-	// repository (for example, Tailscale's proprietary code, or the
-	// Android OSS repository). Together, GitCommit and ExtraGitCommit
-	// exactly describe what repositories and commits were used in a
-	// build.
-	ExtraGitCommit = ""
-
-	// isUnstable is whether the current build appears to be an unstable, i.e. with
-	// an odd minor version number.
-	isUnstable bool
-
-	// legacyOS is runtime.GOOS, except on apple devices where it's either "iOS" or
-	// "macOS" (with that exact case).
-	//
-	// This used to be a thing because Go reported both macOS and iOS as "darwin"
-	// and we needed to tell them apart. But then Go learned GOOS=ios and
-	// GOOS=darwin as separate things, but we're still stuck with this function
-	// because of the odd casing we picked, which has ossified into databases.
-	legacyOS string
-
-	// isMobile is whether the current build is for a mobile device.
-	isMobile bool
-
-	// isSandboxedMacOS is whether the current binary is any binary in the mac store
-	// or standalone sysext mac apps.
-	isSandboxedMacOS bool
-
-	// isMacSysExt is whether the current binary is the mac system extension binary.
-	isMacSysExt bool
-
-	// isWindowsGUI is whether the current binary is the Windows GUI binary.
-	isWindowsGUI bool
-
-	// majorMinorPatch is the major.minor.patch portion of Short.
-	majorMinorPatch string
-)
 
 func init() {
-	initVersion()
-	initUnstable()
-	initMiscTraits()
-}
-
-func initVersion() {
 	defer func() {
 		// Must be run after Short has been initialized, easiest way to do that
 		// is a defer.
@@ -139,38 +75,28 @@ func initVersion() {
 	Long = Short + "-t" + commitHashAbbrev + dirty
 }
 
-func initUnstable() {
+// GitCommit, if non-empty, is the git commit of the
-	_, rest, ok := strings.Cut(Short, ".")
+// github.com/tailscale/tailscale repository at which Tailscale was
-	if !ok {
+// built. Its format is the one returned by `git describe --always
-		return
+// --exclude "*" --dirty --abbrev=200`.
-	}
+var GitCommit = ""
-	minorStr, _, ok := strings.Cut(rest, ".")
-	if !ok {
-		return
-	}
-	minor, err := strconv.Atoi(minorStr)
-	if err != nil {
-		return
-	}
-	isUnstable = minor%2 == 1
-}
 
-func initMiscTraits() {
+// GitDirty is whether Go stamped the binary as having dirty version
-	exe, _ := os.Executable()
+// control changes in the working directory (debug.ReadBuildInfo
-	base := filepath.Base(exe)
+// setting "vcs.modified" was true).
+var GitDirty bool
 
-	legacyOS = runtime.GOOS
+// ExtraGitCommit, if non-empty, is the git commit of a "supplemental"
-	switch runtime.GOOS {
+// repository at which Tailscale was built. Its format is the same as
-	case "darwin":
+// gitCommit.
-		legacyOS = "macOS"
+//
-		isMacSysExt = strings.HasPrefix(base, "io.tailscale.ipn.macsys.network-extension")
+// ExtraGitCommit is used to track the source revision when the main
-		isSandboxedMacOS = isMacSysExt || strings.HasSuffix(exe, "/Contents/MacOS/Tailscale") || strings.HasSuffix(exe, "/Contents/MacOS/IPNExtension")
+// Tailscale repository is integrated into and built from another
-	case "ios":
+// repository (for example, Tailscale's proprietary code, or the
-		legacyOS = "iOS"
+// Android OSS repository). Together, GitCommit and ExtraGitCommit
-		isMobile = true
+// exactly describe what repositories and commits were used in a
-	case "android":
+// build.
-		isMobile = true
+var ExtraGitCommit = ""
-	case "windows":
+
-		isWindowsGUI = strings.EqualFold(base, "tailscale-ipn.exe") || strings.EqualFold(base, "tailscale-ipn")
+// majorMinorPatch is the major.minor.patch portion of Short.
-	}
+var majorMinorPatch string
-}