feature/featuretags: add auto-generated constants for all modular features

So code (in upcoming PRs) can test for the build tags with consts and
get dead code elimination from the compiler+linker.

Updates #12614

Change-Id: If6160453ffd01b798f09894141e7631a93385941
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/featuretags/featuretags.go

@@ -30,7 +30,7 @@ func main() {
 
 	if *list {
 		for _, f := range slices.Sorted(maps.Keys(features)) {
-			fmt.Printf("%20s: %s\n", f, features[f])
+			fmt.Printf("%20s: %s\n", f, features[f].Desc)
 		}
 		return
 	}

feature/featuretags/feature_aws_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_aws
+
+package featuretags
+
+// AWS is whether the binary was built with support for modular feature "AWS integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_aws" build tag.
+// It's a const so it can be used for dead code elimination.
+const AWS = false

feature/featuretags/feature_aws_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_aws
+
+package featuretags
+
+// AWS is whether the binary was built with support for modular feature "AWS integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_aws" build tag.
+// It's a const so it can be used for dead code elimination.
+const AWS = true

feature/featuretags/feature_bird_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_bird
+
+package featuretags
+
+// Bird is whether the binary was built with support for modular feature "Bird BGP integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_bird" build tag.
+// It's a const so it can be used for dead code elimination.
+const Bird = false

feature/featuretags/feature_bird_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_bird
+
+package featuretags
+
+// Bird is whether the binary was built with support for modular feature "Bird BGP integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_bird" build tag.
+// It's a const so it can be used for dead code elimination.
+const Bird = true

feature/featuretags/feature_capture_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_capture
+
+package featuretags
+
+// Capture is whether the binary was built with support for modular feature "Packet capture".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_capture" build tag.
+// It's a const so it can be used for dead code elimination.
+const Capture = false

feature/featuretags/feature_capture_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_capture
+
+package featuretags
+
+// Capture is whether the binary was built with support for modular feature "Packet capture".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_capture" build tag.
+// It's a const so it can be used for dead code elimination.
+const Capture = true

feature/featuretags/feature_completion_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_completion
+
+package featuretags
+
+// Completion is whether the binary was built with support for modular feature "CLI shell completion".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_completion" build tag.
+// It's a const so it can be used for dead code elimination.
+const Completion = false

feature/featuretags/feature_completion_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_completion
+
+package featuretags
+
+// Completion is whether the binary was built with support for modular feature "CLI shell completion".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_completion" build tag.
+// It's a const so it can be used for dead code elimination.
+const Completion = true

feature/featuretags/feature_debugeventbus_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_debugeventbus
+
+package featuretags
+
+// DebugEventBus is whether the binary was built with support for modular feature "eventbus debug support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_debugeventbus" build tag.
+// It's a const so it can be used for dead code elimination.
+const DebugEventBus = false

feature/featuretags/feature_debugeventbus_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_debugeventbus
+
+package featuretags
+
+// DebugEventBus is whether the binary was built with support for modular feature "eventbus debug support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_debugeventbus" build tag.
+// It's a const so it can be used for dead code elimination.
+const DebugEventBus = true

feature/featuretags/feature_desktop_sessions_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_desktop_sessions
+
+package featuretags
+
+// DesktopSessions is whether the binary was built with support for modular feature "Desktop sessions support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_desktop_sessions" build tag.
+// It's a const so it can be used for dead code elimination.
+const DesktopSessions = false

feature/featuretags/feature_desktop_sessions_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_desktop_sessions
+
+package featuretags
+
+// DesktopSessions is whether the binary was built with support for modular feature "Desktop sessions support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_desktop_sessions" build tag.
+// It's a const so it can be used for dead code elimination.
+const DesktopSessions = true

feature/featuretags/feature_drive_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_drive
+
+package featuretags
+
+// Drive is whether the binary was built with support for modular feature "Tailscale Drive (file server) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_drive" build tag.
+// It's a const so it can be used for dead code elimination.
+const Drive = false

feature/featuretags/feature_drive_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_drive
+
+package featuretags
+
+// Drive is whether the binary was built with support for modular feature "Tailscale Drive (file server) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_drive" build tag.
+// It's a const so it can be used for dead code elimination.
+const Drive = true

feature/featuretags/feature_kube_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_kube
+
+package featuretags
+
+// Kube is whether the binary was built with support for modular feature "Kubernetes integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_kube" build tag.
+// It's a const so it can be used for dead code elimination.
+const Kube = false

feature/featuretags/feature_kube_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_kube
+
+package featuretags
+
+// Kube is whether the binary was built with support for modular feature "Kubernetes integration".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_kube" build tag.
+// It's a const so it can be used for dead code elimination.
+const Kube = true

feature/featuretags/feature_relayserver_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_relayserver
+
+package featuretags
+
+// RelayServer is whether the binary was built with support for modular feature "Relay server".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_relayserver" build tag.
+// It's a const so it can be used for dead code elimination.
+const RelayServer = false

feature/featuretags/feature_relayserver_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_relayserver
+
+package featuretags
+
+// RelayServer is whether the binary was built with support for modular feature "Relay server".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_relayserver" build tag.
+// It's a const so it can be used for dead code elimination.
+const RelayServer = true

feature/featuretags/feature_serve_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_serve
+
+package featuretags
+
+// Serve is whether the binary was built with support for modular feature "Serve and Funnel support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_serve" build tag.
+// It's a const so it can be used for dead code elimination.
+const Serve = false

feature/featuretags/feature_serve_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_serve
+
+package featuretags
+
+// Serve is whether the binary was built with support for modular feature "Serve and Funnel support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_serve" build tag.
+// It's a const so it can be used for dead code elimination.
+const Serve = true

feature/featuretags/feature_ssh_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_ssh
+
+package featuretags
+
+// SSH is whether the binary was built with support for modular feature "Tailscale SSH support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_ssh" build tag.
+// It's a const so it can be used for dead code elimination.
+const SSH = false

feature/featuretags/feature_ssh_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_ssh
+
+package featuretags
+
+// SSH is whether the binary was built with support for modular feature "Tailscale SSH support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_ssh" build tag.
+// It's a const so it can be used for dead code elimination.
+const SSH = true

feature/featuretags/feature_syspolicy_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_syspolicy
+
+package featuretags
+
+// SystemPolicy is whether the binary was built with support for modular feature "System policy configuration (MDM) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_syspolicy" build tag.
+// It's a const so it can be used for dead code elimination.
+const SystemPolicy = false

feature/featuretags/feature_syspolicy_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_syspolicy
+
+package featuretags
+
+// SystemPolicy is whether the binary was built with support for modular feature "System policy configuration (MDM) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_syspolicy" build tag.
+// It's a const so it can be used for dead code elimination.
+const SystemPolicy = true

feature/featuretags/feature_systray_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_systray
+
+package featuretags
+
+// SysTray is whether the binary was built with support for modular feature "Linux system tray".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_systray" build tag.
+// It's a const so it can be used for dead code elimination.
+const SysTray = false

feature/featuretags/feature_systray_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_systray
+
+package featuretags
+
+// SysTray is whether the binary was built with support for modular feature "Linux system tray".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_systray" build tag.
+// It's a const so it can be used for dead code elimination.
+const SysTray = true

feature/featuretags/feature_taildrop_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_taildrop
+
+package featuretags
+
+// Taildrop is whether the binary was built with support for modular feature "Taildrop (file sending) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_taildrop" build tag.
+// It's a const so it can be used for dead code elimination.
+const Taildrop = false

feature/featuretags/feature_taildrop_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_taildrop
+
+package featuretags
+
+// Taildrop is whether the binary was built with support for modular feature "Taildrop (file sending) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_taildrop" build tag.
+// It's a const so it can be used for dead code elimination.
+const Taildrop = true

feature/featuretags/feature_tailnetlock_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_tailnetlock
+
+package featuretags
+
+// TailnetLock is whether the binary was built with support for modular feature "Tailnet Lock support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tailnetlock" build tag.
+// It's a const so it can be used for dead code elimination.
+const TailnetLock = false

feature/featuretags/feature_tailnetlock_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_tailnetlock
+
+package featuretags
+
+// TailnetLock is whether the binary was built with support for modular feature "Tailnet Lock support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tailnetlock" build tag.
+// It's a const so it can be used for dead code elimination.
+const TailnetLock = true

feature/featuretags/feature_tap_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_tap
+
+package featuretags
+
+// Tap is whether the binary was built with support for modular feature "Experimental Layer 2 (ethernet) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tap" build tag.
+// It's a const so it can be used for dead code elimination.
+const Tap = false

feature/featuretags/feature_tap_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_tap
+
+package featuretags
+
+// Tap is whether the binary was built with support for modular feature "Experimental Layer 2 (ethernet) support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tap" build tag.
+// It's a const so it can be used for dead code elimination.
+const Tap = true

feature/featuretags/feature_tpm_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_tpm
+
+package featuretags
+
+// TPM is whether the binary was built with support for modular feature "TPM support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tpm" build tag.
+// It's a const so it can be used for dead code elimination.
+const TPM = false

feature/featuretags/feature_tpm_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_tpm
+
+package featuretags
+
+// TPM is whether the binary was built with support for modular feature "TPM support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_tpm" build tag.
+// It's a const so it can be used for dead code elimination.
+const TPM = true

feature/featuretags/feature_wakeonlan_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_wakeonlan
+
+package featuretags
+
+// WakeOnLAN is whether the binary was built with support for modular feature "Wake-on-LAN support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_wakeonlan" build tag.
+// It's a const so it can be used for dead code elimination.
+const WakeOnLAN = false

feature/featuretags/feature_wakeonlan_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_wakeonlan
+
+package featuretags
+
+// WakeOnLAN is whether the binary was built with support for modular feature "Wake-on-LAN support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_wakeonlan" build tag.
+// It's a const so it can be used for dead code elimination.
+const WakeOnLAN = true

feature/featuretags/feature_webclient_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build ts_omit_webclient
+
+package featuretags
+
+// WebClient is whether the binary was built with support for modular feature "Web client support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_webclient" build tag.
+// It's a const so it can be used for dead code elimination.
+const WebClient = false

feature/featuretags/feature_webclient_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen-featuretags.go; DO NOT EDIT.
+
+//go:build !ts_omit_webclient
+
+package featuretags
+
+// WebClient is whether the binary was built with support for modular feature "Web client support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_webclient" build tag.
+// It's a const so it can be used for dead code elimination.
+const WebClient = true

feature/featuretags/featuretags.go

@@ -1,6 +1,8 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+//go:generate go run gen-featuretags.go
+
 // The featuretags package is a registry of all the ts_omit-able build tags.
 package featuretags
 
@@ -32,26 +34,34 @@ func (ft FeatureTag) OmitTag() string {
 	return "ts_omit_" + string(ft)
 }
 
+// FeatureMeta describes a modular feature that can be conditionally linked into
+// the binary.
+type FeatureMeta struct {
+	Sym  string // exported Go symbol for boolean const
+	Desc string // human-readable description
+}
+
 // Features are the known Tailscale features that can be selectively included or
 // excluded via build tags, and a description of each.
-var Features = map[FeatureTag]string{
-	"aws":              "AWS integration",
-	"bird":             "Bird BGP integration",
-	"capture":          "Packet capture",
-	"cli":              "embed the CLI into the tailscaled binary",
-	"completion":       "CLI shell completion",
-	"debugeventbus":    "eventbus debug support",
-	"desktop_sessions": "Desktop sessions support",
-	"drive":            "Tailscale Drive (file server) support",
-	"kube":             "Kubernetes integration",
-	"relayserver":      "Relay server",
-	"ssh":              "Tailscale SSH support",
-	"syspolicy":        "System policy configuration (MDM) support",
-	"systray":          "Linux system tray",
-	"taildrop":         "Taildrop (file sending) support",
-	"tailnetlock":      "Tailnet Lock support",
-	"tap":              "Experimental Layer 2 (ethernet) support",
-	"tpm":              "TPM support",
-	"wakeonlan":        "Wake-on-LAN support",
-	"webclient":        "Web client support",
+var Features = map[FeatureTag]FeatureMeta{
+	"aws":              {"AWS", "AWS integration"},
+	"bird":             {"Bird", "Bird BGP integration"},
+	"capture":          {"Capture", "Packet capture"},
+	"cli":              {"CLI", "embed the CLI into the tailscaled binary"},
+	"completion":       {"Completion", "CLI shell completion"},
+	"debugeventbus":    {"DebugEventBus", "eventbus debug support"},
+	"desktop_sessions": {"DesktopSessions", "Desktop sessions support"},
+	"drive":            {"Drive", "Tailscale Drive (file server) support"},
+	"kube":             {"Kube", "Kubernetes integration"},
+	"relayserver":      {"RelayServer", "Relay server"},
+	"serve":            {"Serve", "Serve and Funnel support"},
+	"ssh":              {"SSH", "Tailscale SSH support"},
+	"syspolicy":        {"SystemPolicy", "System policy configuration (MDM) support"},
+	"systray":          {"SysTray", "Linux system tray"},
+	"taildrop":         {"Taildrop", "Taildrop (file sending) support"},
+	"tailnetlock":      {"TailnetLock", "Tailnet Lock support"},
+	"tap":              {"Tap", "Experimental Layer 2 (ethernet) support"},
+	"tpm":              {"TPM", "TPM support"},
+	"wakeonlan":        {"WakeOnLAN", "Wake-on-LAN support"},
+	"webclient":        {"WebClient", "Web client support"},
 }

feature/featuretags/gen-featuretags.go

@@ -0,0 +1,49 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ignore
+
+// The gen-featuretags.go program generates the feature_<feature>_enabled.go
+// and feature_<feature>_disabled.go files for each feature tag.
+package main
+
+import (
+	"cmp"
+	"fmt"
+	"os"
+	"strings"
+
+	"tailscale.com/feature/featuretags"
+	"tailscale.com/util/must"
+)
+
+const header = `// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code g|e|n|e|r|a|t|e|d by gen-featuretags.go; D|O N|OT E|D|I|T.
+
+`
+
+func main() {
+	header := strings.ReplaceAll(header, "|", "") // to avoid this file being marked as generated
+	for k, m := range featuretags.Features {
+		if !k.IsOmittable() {
+			continue
+		}
+		sym := cmp.Or(m.Sym, strings.ToUpper(string(k)[:1])+string(k)[1:])
+		for _, suf := range []string{"enabled", "disabled"} {
+			bang := ""
+			if suf == "enabled" {
+				bang = "!" // !ts_omit_...
+			}
+			must.Do(os.WriteFile("feature_"+string(k)+"_"+suf+".go",
+				fmt.Appendf(nil, "%s//go:build %s%s\n\npackage featuretags\n\n"+
+					"// %s is whether the binary was built with support for modular feature %q.\n"+
+					"// Specifically, it's whether the binary was NOT built with the %q build tag.\n"+
+					"// It's a const so it can be used for dead code elimination.\n"+
+					"const %s = %t\n",
+					header, bang, k.OmitTag(), sym, m.Desc, k.OmitTag(), sym, suf == "enabled"), 0644))
+
+		}
+	}
+}