feat: ensure the config is fully parsed

Return an error otherwise.

This actually helped to find an error in 4.9 config (which is fixed).
Before the fix, the error looked like this:

> Error: unknown keys in config: [node."podman-catatonit-3.2.3-0.12.module+el8.4.0+14908+81312c48.x86_64".filter_images]

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

dist/releases/4.9/config.toml

@@ -24,6 +24,9 @@ filter_files = [
   "/sbin/ldconfig",
 ]
 
+# List of images to ignore.
+filter_images = [ ]
+
 # these node exceptions via rpm have been manually validated
 [node."cri-o-1.22.5-20.rhaos4.9.gitdf6ec18.el8.x86_64"]
 filter_files = [
@@ -39,9 +42,6 @@ filter_files = [ "/usr/bin/pinns" ]
 [node."podman-catatonit-3.2.3-0.12.module+el8.4.0+14908+81312c48.x86_64"]
 filter_files = [ "/usr/libexec/catatonit/catatonit" ]
 
-# List of images to ignore.
-filter_images = [ ]
-
 # Payload Components
 
 [payload.multus-cni-alt-container]

main.go

@@ -216,7 +216,23 @@ func main() {
 	}
 }
 
-func getConfig(config *Config) error {
+func getConfig(config *Config) (retErr error) {
+	var (
+		res toml.MetaData
+		err error
+	)
+
+	// Check if the configuration was fully parsed.
+	defer func() {
+		if retErr != nil {
+			return
+		}
+		un := res.Undecoded()
+		if len(un) != 0 {
+			retErr = fmt.Errorf("unknown keys in config: %+v", un)
+		}
+	}()
+
 	// Handle --config-for-version first.
 	if configForVersion != "" {
 		if configFile != "" {
@@ -226,7 +242,7 @@ func getConfig(config *Config) error {
 		if err != nil {
 			return err
 		}
-		_, err = toml.Decode(string(cfg), &config)
+		res, err = toml.Decode(string(cfg), &config)
 		if err != nil { // Should never happen.
 			panic("invalid embedded config: " + err.Error())
 		}
@@ -238,7 +254,7 @@ func getConfig(config *Config) error {
 	if file == "" {
 		file = defaultConfigFile
 	}
-	_, err := toml.DecodeFile(file, &config)
+	res, err = toml.DecodeFile(file, &config)
 	if err == nil {
 		klog.Infof("using config file: %v", file)
 		return nil
@@ -248,7 +264,7 @@ func getConfig(config *Config) error {
 	// defaultConfigFile is not found, fall back to embedded config.
 	if errors.Is(err, os.ErrNotExist) && configFile == "" {
 		klog.Info("using embedded config")
-		_, err = toml.Decode(embeddedConfig, &config)
+		res, err = toml.Decode(embeddedConfig, &config)
 		if err != nil { // Should never happen.
 			panic("invalid embedded config: " + err.Error())
 		}