From b68764f86c4c14056e2e8aa3763d32307e88cff3 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Thu, 9 Apr 2020 17:04:11 -0700
Subject: [PATCH] build/version: check AppPreRelease semantics in init()

We'll do the validation during construction of the runtime so that we
can safely use the AppPreRelease field externally without needing to
normalize it.
---
 build/version.go | 40 ++++++++++++++++++----------------------
 1 file changed, 18 insertions(+), 22 deletions(-)

diff --git a/build/version.go b/build/version.go
index 855d9127c..4985ed6cc 100644
--- a/build/version.go
+++ b/build/version.go
@@ -6,7 +6,6 @@
 package build
 
 import (
-	"bytes"
 	"fmt"
 	"strings"
 )
@@ -36,19 +35,30 @@ const (
 	AppPreRelease = "beta"
 )
 
+func init() {
+	// Assert that AppPreRelease is valid according to the semantic
+	// versioning guidelines for pre-release version and build metadata
+	// strings. In particular it MUST only contain characters in
+	// semanticAlphabet.
+	for _, r := range AppPreRelease {
+		if !strings.ContainsRune(semanticAlphabet, r) {
+			panic(fmt.Errorf("rune: %v is not in the semantic "+
+				"alphabet", r))
+		}
+	}
+}
+
 // Version returns the application version as a properly formed string per the
 // semantic versioning 2.0.0 spec (http://semver.org/).
 func Version() string {
 	// Start with the major, minor, and patch versions.
 	version := fmt.Sprintf("%d.%d.%d", AppMajor, AppMinor, AppPatch)
 
-	// Append pre-release version if there is one.  The hyphen called for
-	// by the semantic versioning spec is automatically appended and should
-	// not be contained in the pre-release string.  The pre-release version
-	// is not appended if it contains invalid characters.
-	preRelease := normalizeVerString(AppPreRelease)
-	if preRelease != "" {
-		version = fmt.Sprintf("%s-%s", version, preRelease)
+	// Append pre-release version if there is one. The hyphen called for by
+	// the semantic versioning spec is automatically appended and should not
+	// be contained in the pre-release string.
+	if AppPreRelease != "" {
+		version = fmt.Sprintf("%s-%s", version, AppPreRelease)
 	}
 
 	// Append commit hash of current build to version.
@@ -56,17 +66,3 @@ func Version() string {
 
 	return version
 }
-
-// normalizeVerString returns the passed string stripped of all characters which
-// are not valid according to the semantic versioning guidelines for pre-release
-// version and build metadata strings.  In particular they MUST only contain
-// characters in semanticAlphabet.
-func normalizeVerString(str string) string {
-	var result bytes.Buffer
-	for _, r := range str {
-		if strings.ContainsRune(semanticAlphabet, r) {
-			result.WriteRune(r)
-		}
-	}
-	return result.String()
-}