feature/buildfeatures: split const bools out of the featuretags package, add Has prefix

This renames the package+symbols in the earlier 17ffa80138 to be in their own package ("buildfeatures") and start with the word "Has" like "if buildfeatures.HasFoo {". Updates #12614 Change-Id: I510e5f65993e5b76a0e163e3aa4543755213cbf6 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2025-09-15 09:52:17 -07:00
parent 510830ca7a
commit 6fb316f5ed
41 changed files with 166 additions and 158 deletions
@@ -0,0 +1,49 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ignore
+
+// The gens.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.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 := "Has" + 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 buildfeatures\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))
+
+		}
+	}
+}