Fixes #897: Adds error handling to the configuration file parsing pro…

…cess by adding more information to the error messsages (if any) that are returned when the configuration file cannot be parsed correctly

control/config.go

@@ -103,23 +103,23 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		switch k {
 		case "max_running_plugins":
 			if err := json.Unmarshal(v, &(c.MaxRunningPlugins)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'control::max_running_plugins')", err)
 			}
 		case "plugin_trust_level":
 			if err := json.Unmarshal(v, &(c.PluginTrust)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'control::plugin_trust_level')", err)
 			}
 		case "auto_discover_path":
 			if err := json.Unmarshal(v, &(c.AutoDiscoverPath)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'control::auto_discover_path')", err)
 			}
 		case "keyring_paths":
 			if err := json.Unmarshal(v, &(c.KeyringPaths)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'control::keyring_paths')", err)
 			}
 		case "cache_expiration":
 			if err := json.Unmarshal(v, &(c.CacheExpiration)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'control::cache_expiration')", err)
 			}
 		case "plugins":
 			if err := json.Unmarshal(v, c.Plugins); err != nil {

mgmt/rest/server.go

@@ -200,31 +200,31 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		switch k {
 		case "enable":
 			if err := json.Unmarshal(v, &(c.Enable)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::enable')", err)
 			}
 		case "port":
 			if err := json.Unmarshal(v, &(c.Port)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::port')", err)
 			}
 		case "https":
 			if err := json.Unmarshal(v, &(c.HTTPS)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::https')", err)
 			}
 		case "rest_certificate":
 			if err := json.Unmarshal(v, &(c.RestCertificate)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::rest_certificate')", err)
 			}
 		case "rest_key":
 			if err := json.Unmarshal(v, &(c.RestKey)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::rest_key')", err)
 			}
 		case "rest_auth":
 			if err := json.Unmarshal(v, &(c.RestAuth)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::rest_auth')", err)
 			}
 		case "rest_auth_password":
 			if err := json.Unmarshal(v, &(c.RestAuthPassword)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'restapi::rest_auth_password')", err)
 			}
 		}
 	}

mgmt/tribe/config.go

@@ -21,6 +21,7 @@ package tribe
 
 import (
 	"encoding/json"
+	"fmt"
 	"net"
 	"os"
 	"time"
@@ -93,23 +94,23 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		switch k {
 		case "name":
 			if err := json.Unmarshal(v, &(c.Name)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'tribe::name')", err)
 			}
 		case "enable":
 			if err := json.Unmarshal(v, &(c.Enable)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'tribe::enable')", err)
 			}
 		case "bind_addr":
 			if err := json.Unmarshal(v, &(c.BindAddr)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'tribe::bind_addr')", err)
 			}
 		case "bind_port":
 			if err := json.Unmarshal(v, &(c.BindPort)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'tribe::bind_port')", err)
 			}
 		case "seed":
 			if err := json.Unmarshal(v, &(c.Seed)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'tribe::seed')", err)
 			}
 		}
 	}

pkg/cfgfile/cfgfile.go

@@ -20,28 +20,33 @@ limitations under the License.
 package cfgfile
 
 import (
-	"encoding/json"
 	"fmt"
 	"io/ioutil"
+	"strings"
 
 	"github.com/ghodss/yaml"
 )
 
-//
+// Read an input configuration file, parsing it (as YAML or JSON)
+// into the input 'interface{}'', v
 func Read(path string, v interface{}) error {
 	// read bytes from file
 	b, err := ioutil.ReadFile(path)
 	if err != nil {
 		return err
 	}
-
-	// Try to unmarshal the byte array, first in YAML, then JSON. If both
-	// fail to unmarshal the blob read above, then return an error.
-	if err := yaml.Unmarshal(b, v); err == nil {
-		return nil
-	}
-	if err := json.Unmarshal(b, v); err == nil {
-		return nil
+	// parse the byte-stream read (above); Note that we can parse both JSON
+	// and YAML using the same yaml.Unmarshal() method since a JSON string is
+	// a valid YAML string (but the converse is not true)
+	if parseErr := yaml.Unmarshal(b, v); parseErr != nil {
+		// remove any YAML-specific prefix that might have been added by then
+		// yaml.Unmarshal() method or JSON-specific prefix that might have been
+		// added if the resulting JSON string could not be marshalled into our
+		// input interface correctly (note, if there is no match to either of
+		// these prefixes then the error message will be passed through unchanged)
+		tmpErr := strings.TrimPrefix(parseErr.Error(), "error converting YAML to JSON: yaml: ")
+		errRet := strings.TrimPrefix(tmpErr, "error unmarshaling JSON: json: ")
+		return fmt.Errorf("Error while parsing configuration file: %v", errRet)
 	}
-	return fmt.Errorf("Unknown file type")
+	return nil
 }

scheduler/config.go

@@ -19,7 +19,10 @@ limitations under the License.
 
 package scheduler
 
-import "encoding/json"
+import (
+	"encoding/json"
+	"fmt"
+)
 
 // default configuration values
 const (
@@ -60,11 +63,11 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		switch k {
 		case "work_manager_queue_size":
 			if err := json.Unmarshal(v, &(c.WorkManagerQueueSize)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'scheduler::work_manager_queue_size')", err)
 			}
 		case "work_manager_pool_size":
 			if err := json.Unmarshal(v, &(c.WorkManagerPoolSize)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'scheduler::work_manager_pool_size')", err)
 			}
 		}
 	}

snapd.go

@@ -722,15 +722,15 @@ func (c *Config) UnmarshalJSON(data []byte) error {
 		switch k {
 		case "log_level":
 			if err := json.Unmarshal(v, &(c.LogLevel)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'log_level')", err)
 			}
 		case "gomaxprocs":
 			if err := json.Unmarshal(v, &(c.GoMaxProcs)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'gomaxprocs')", err)
 			}
 		case "log_path":
 			if err := json.Unmarshal(v, &(c.LogPath)); err != nil {
-				return err
+				return fmt.Errorf("%v (while parsing 'log_path')", err)
 			}
 		case "control":
 			if err := json.Unmarshal(v, c.Control); err != nil {