fix: automatically trim label lists around the commas to remove whitespace

internal/app/cmd/register.go

@@ -172,7 +172,7 @@ func (r *registerInputs) assignToNext(stage registerStage, value string, cfg *co
 	case StageInputLabels:
 		r.Labels = defaultLabels
 		if value != "" {
-			r.Labels = strings.Split(value, ",")
+			r.Labels = commaSplit(value)
 		}
 
 		if validateLabels(r.Labels) != nil {
@@ -260,7 +260,7 @@ func registerNoInteractive(ctx context.Context, configFile string, regArgs *regi
 	regArgs.Labels = strings.TrimSpace(regArgs.Labels)
 	// command line flag.
 	if regArgs.Labels != "" {
-		inputs.Labels = strings.Split(regArgs.Labels, ",")
+		inputs.Labels = commaSplit(regArgs.Labels)
 	}
 	// specify labels in config file.
 	if len(cfg.Runner.Labels) > 0 {
@@ -353,3 +353,24 @@ func doRegister(ctx context.Context, cfg *config.Config, inputs *registerInputs)
 	}
 	return nil
 }
+
+// Splits a string by commas, but trims whitespace around the commas. Used for label parsing to avoid a rogue whitespace
+// like "docker:docker://node:22-bookworm, self-hosted:host, lxc:lxc://debian:bookworm" becoming labeled with
+// " self-hosted" and " lxc".
+func commaSplit(s string) []string {
+	if s == "" {
+		return make([]string, 0)
+	}
+
+	parts := strings.Split(s, ",")
+	result := make([]string, 0, len(parts))
+
+	for _, part := range parts {
+		trimmed := strings.TrimSpace(part)
+		if trimmed != "" {
+			result = append(result, trimmed)
+		}
+	}
+
+	return result
+}

internal/app/cmd/register_test.go

@@ -0,0 +1,31 @@
+// Copyright 2025 The Forgejo Authors
+// SPDX-License-Identifier: MIT
+
+package cmd
+
+import (
+	"slices"
+	"testing"
+)
+
+func TestCommaSplit(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected []string
+	}{
+		{"", []string{}},
+		{"abc", []string{"abc"}},
+		{"abc,def", []string{"abc", "def"}},
+		{"abc, def", []string{"abc", "def"}},
+		{" abc , def ", []string{"abc", "def"}},
+		{"abc,  ,def", []string{"abc", "def"}},
+		{" , , ", []string{}},
+	}
+
+	for _, test := range tests {
+		result := commaSplit(test.input)
+		if !slices.Equal(result, test.expected) {
+			t.Errorf("commaSplit(%q) = %v, want %v", test.input, result, test.expected)
+		}
+	}
+}