Unwrap aggregates of size 1 when writing errors

pkg/kubectl/cmd/get.go

@@ -301,22 +301,23 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 			return err
 		}
 
-		allErrs := []error{}
+		// the outermost object will be converted to the output-version, but inner
+		// objects can use their mappings
+		version, err := cmdutil.OutputVersion(cmd, clientConfig.GroupVersion)
+		if err != nil {
+			return err
+		}
+
+		var errs []error
 		singular := false
 		infos, err := r.IntoSingular(&singular).Infos()
 		if err != nil {
 			if singular {
 				return err
 			}
-			allErrs = append(allErrs, err)
+			errs = append(errs, err)
 		}
 
-		// the outermost object will be converted to the output-version, but inner
-		// objects can use their mappings
-		version, err := cmdutil.OutputVersion(cmd, clientConfig.GroupVersion)
-		if err != nil {
-			return err
-		}
 		res := ""
 		if len(infos) > 0 {
 			res = infos[0].ResourceMapping().Resource
@@ -329,20 +330,20 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 
 		isList := meta.IsListType(obj)
 		if isList {
-			filteredResourceCount, items, errs := cmdutil.FilterResourceList(obj, filterFuncs, filterOpts)
-			if errs != nil {
-				return errs
+			filteredResourceCount, items, err := cmdutil.FilterResourceList(obj, filterFuncs, filterOpts)
+			if err != nil {
+				return err
 			}
 			filteredObj, err := cmdutil.ObjectListToVersionedObject(items, version)
 			if err != nil {
 				return err
 			}
 			if err := printer.PrintObj(filteredObj, out); err != nil {
-				allErrs = append(allErrs, err)
+				errs = append(errs, err)
 			}
 
 			cmdutil.PrintFilterCount(filteredResourceCount, res, errOut, filterOpts)
-			return utilerrors.NewAggregate(allErrs)
+			return utilerrors.Reduce(utilerrors.Flatten(utilerrors.NewAggregate(errs)))
 		}
 
 		filteredResourceCount := 0
@@ -350,14 +351,14 @@ func RunGet(f *cmdutil.Factory, out io.Writer, errOut io.Writer, cmd *cobra.Comm
 			if err != nil {
 				glog.V(2).Infof("Unable to filter resource: %v", err)
 			} else if err := printer.PrintObj(obj, out); err != nil {
-				allErrs = append(allErrs, err)
+				errs = append(errs, err)
 			}
 		} else if isFiltered {
 			filteredResourceCount++
 		}
 
 		cmdutil.PrintFilterCount(filteredResourceCount, res, errOut, filterOpts)
-		return utilerrors.NewAggregate(allErrs)
+		return utilerrors.Reduce(utilerrors.Flatten(utilerrors.NewAggregate(errs)))
 	}
 
 	allErrs := []error{}

pkg/kubectl/cmd/util/helpers.go

@@ -122,6 +122,11 @@ func checkErrWithPrefix(prefix string, err error) {
 // checkErr formats a given error as a string and calls the passed handleErr
 // func with that string and an kubectl exit code.
 func checkErr(prefix string, err error, handleErr func(string, int)) {
+	// unwrap aggregates of 1
+	if agg, ok := err.(utilerrors.Aggregate); ok && len(agg.Errors()) == 1 {
+		err = agg.Errors()[0]
+	}
+
 	switch {
 	case err == nil:
 		return

pkg/util/errors/errors.go

@@ -147,6 +147,20 @@ func Flatten(agg Aggregate) Aggregate {
 	return NewAggregate(result)
 }
 
+// Reduce will return err or, if err is an Aggregate and only has one item,
+// the first item in the aggregate.
+func Reduce(err error) error {
+	if agg, ok := err.(Aggregate); ok && err != nil {
+		switch len(agg.Errors()) {
+		case 1:
+			return agg.Errors()[0]
+		case 0:
+			return nil
+		}
+	}
+	return err
+}
+
 // AggregateGoroutines runs the provided functions in parallel, stuffing all
 // non-nil errors into the returned Aggregate.
 // Returns nil if all the functions complete successfully.