Remove allocations from SemVer scheme validation

normalization.go

@@ -89,16 +89,16 @@ func normalizeVersionForScheme(version, scheme string) (string, error) {
 }
 
 func validSemverLike(s string) bool {
-	m := SemanticVersionRegex.FindStringSubmatch(s)
-	if m == nil {
+	parsed, ok := parseSemverValue(s)
+	if !ok {
 		return false
 	}
-	for _, field := range []string{m[4], m[5]} {
+	for _, field := range []string{parsed.pre, semverBuild(s)} {
 		if field == "" {
 			continue
 		}
-		for _, part := range strings.Split(field, ".") {
-			if part == "" || strings.Trim(part, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-") != "" {
+		for part := range strings.SplitSeq(field, ".") {
+			if part == "" || !validGoIdentifier(part) {
 				return false
 			}
 		}

semver_validation_test.go

@@ -0,0 +1,75 @@
+package vers
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestSemverValidation(t *testing.T) {
+	tests := []struct {
+		version string
+		valid   bool
+	}{
+		{"1", true}, {"1.2", true}, {"1.2.3", true},
+		{"v01.002.0003", true}, {"1.2.3-alpha.01+build.5", true},
+		{"1.2.3--+0", true}, {"\t1.2.3\r\n", true},
+		{"", false}, {"v", false}, {"V1.2.3", false},
+		{"1.2.3.4", false}, {"1.", false}, {"1..2", false},
+		{"1.2.3-", false}, {"1.2.3+", false},
+		{"1.2.3-alpha..1", false}, {"1.2.3+build..1", false},
+		{"1.2.3-alpha_1", false}, {"1.2.3+é", false},
+		{"1.2.3-alpha\n1", false}, {"1.2.3+a+b", false},
+		{"^1.2.3", false}, {"1.2.x", false},
+	}
+	for _, scheme := range []string{"npm", "semver", "cargo", "go", "golang", "hex", "elixir"} {
+		t.Run(scheme, func(t *testing.T) {
+			for _, tt := range tests {
+				if got := ValidWithScheme(tt.version, scheme); got != tt.valid {
+					t.Errorf("ValidWithScheme(%q, %q) = %v, want %v", tt.version, scheme, got, tt.valid)
+				}
+			}
+		})
+	}
+}
+
+func FuzzSemverValidation(f *testing.F) {
+	for _, version := range []string{"1.2.3", "v01.2", "1.2.3-alpha.01+build.5", "1.2.3-", "1.2.3+", "1.2.3-a\nb", "1.2.3+a+b", "", "1.2.3.4"} {
+		f.Add(version)
+	}
+	f.Fuzz(func(t *testing.T, version string) {
+		want := referenceSemverValidation(strings.TrimSpace(version))
+		if got := ValidWithScheme(version, "npm"); got != want {
+			t.Fatalf("ValidWithScheme(%q, npm) = %v, want %v", version, got, want)
+		}
+	})
+}
+
+// Preserve the regex implementation as an independent compatibility oracle.
+func referenceSemverValidation(version string) bool {
+	m := SemanticVersionRegex.FindStringSubmatch(version)
+	if m == nil {
+		return false
+	}
+	for _, field := range []string{m[4], m[5]} {
+		if field == "" {
+			continue
+		}
+		for _, part := range strings.Split(field, ".") {
+			if part == "" || strings.Trim(part, "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-") != "" {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func BenchmarkValidWithSchemeNPM(b *testing.B) {
+	for _, version := range []string{"1.2.3", "v01.2", "1.2.3-alpha.1+build.5", "1.2.3-alpha..1"} {
+		b.Run(version, func(b *testing.B) {
+			b.ReportAllocs()
+			for b.Loop() {
+				ValidWithScheme(version, "npm")
+			}
+		})
+	}
+}