ParseAll: refactor

Avoid using `strings.Split`, and error on empty values.

Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah

platforms.go

@@ -280,13 +280,9 @@ func Parse(specifier string) (specs.Platform, error) {
 			}
 			p.OSVersion = osVersion
 			if osOptions[3] != "" {
-				rawFeatures := strings.Split(osOptions[3][1:], "+")
-				p.OSFeatures = make([]string, len(rawFeatures))
-				for i, f := range rawFeatures {
-					p.OSFeatures[i], err = decodeOSOption(f)
-					if err != nil {
-						return specs.Platform{}, fmt.Errorf("%q has an invalid OS feature %q: %w", specifier, f, err)
-					}
+				p.OSFeatures, err = parseOSFeatures(osOptions[3][1:])
+				if err != nil {
+					return specs.Platform{}, fmt.Errorf("%q has invalid OS features: %w", specifier, err)
 				}
 			}
 		} else {
@@ -346,6 +342,30 @@ func Parse(specifier string) (specs.Platform, error) {
 	return specs.Platform{}, fmt.Errorf("%q: cannot parse platform specifier: %w", specifier, errInvalidArgument)
 }
 
+func parseOSFeatures(s string) ([]string, error) {
+	if s == "" {
+		return nil, nil
+	}
+
+	var features []string
+	for raw := range strings.SplitSeq(s, "+") {
+		raw = strings.TrimSpace(raw)
+		if raw == "" {
+			return nil, fmt.Errorf("empty os feature: %w", errInvalidArgument)
+		}
+		feature, err := decodeOSOption(raw)
+		if err != nil {
+			return nil, fmt.Errorf("invalid os feature %q: %w", raw, err)
+		}
+		if feature == "" {
+			continue
+		}
+		features = append(features, feature)
+	}
+
+	return features, nil
+}
+
 // MustParse is like Parses but panics if the specifier cannot be parsed.
 // Simplifies initialization of global variables.
 func MustParse(specifier string) specs.Platform {
@@ -371,6 +391,9 @@ func FormatAll(platform specs.Platform) string {
 	if platform.OS == "" {
 		return "unknown"
 	}
+	if platform.OSVersion == "" && len(platform.OSFeatures) == 0 {
+		return path.Join(platform.OS, platform.Architecture, platform.Variant)
+	}
 
 	var b strings.Builder
 	b.WriteString(platform.OS)