Remove string checking in API error handling

Use strongly typed errors to set HTTP status codes.
Error interfaces are defined in the api/errors package and errors
returned from controllers are checked against these interfaces.

Errors can be wraeped in a pkg/errors.Causer, as long as somewhere in the
line of causes one of the interfaces is implemented. The special error
interfaces take precedence over Causer, meaning if both Causer and one
of the new error interfaces are implemented, the Causer is not
traversed.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

api/server/router/network/filter.go

@@ -1,8 +1,6 @@
 package network
 
 import (
-	"fmt"
-
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/filters"
 	"github.com/docker/docker/runconfig"
@@ -24,11 +22,19 @@ func filterNetworkByType(nws []types.NetworkResource, netType string) ([]types.N
 			}
 		}
 	default:
-		return nil, fmt.Errorf("Invalid filter: 'type'='%s'", netType)
+		return nil, invalidFilter(netType)
 	}
 	return retNws, nil
 }
 
+type invalidFilter string
+
+func (e invalidFilter) Error() string {
+	return "Invalid filter: 'type'='" + string(e) + "'"
+}
+
+func (e invalidFilter) InvalidParameter() {}
+
 // filterNetworks filters network list according to user specified filter
 // and returns user chosen networks
 func filterNetworks(nws []types.NetworkResource, filter filters.Args) ([]types.NetworkResource, error) {

api/server/router/network/network_routes.go

@@ -2,14 +2,12 @@ package network
 
 import (
 	"encoding/json"
-	"fmt"
 	"net/http"
 	"strconv"
 	"strings"
 
 	"golang.org/x/net/context"
 
-	"github.com/docker/docker/api/errors"
 	"github.com/docker/docker/api/server/httputils"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/filters"
@@ -18,6 +16,7 @@ import (
 	"github.com/docker/libnetwork"
 	netconst "github.com/docker/libnetwork/datastore"
 	"github.com/docker/libnetwork/networkdb"
+	"github.com/pkg/errors"
 )
 
 var (
@@ -83,6 +82,24 @@ SKIP:
 	return httputils.WriteJSON(w, http.StatusOK, list)
 }
 
+type invalidRequestError struct {
+	cause error
+}
+
+func (e invalidRequestError) Error() string {
+	return e.cause.Error()
+}
+
+func (e invalidRequestError) InvalidParameter() {}
+
+type ambigousResultsError string
+
+func (e ambigousResultsError) Error() string {
+	return "network " + string(e) + " is ambiguous"
+}
+
+func (ambigousResultsError) InvalidParameter() {}
+
 func (n *networkRouter) getNetwork(ctx context.Context, w http.ResponseWriter, r *http.Request, vars map[string]string) error {
 	if err := httputils.ParseForm(r); err != nil {
 		return err
@@ -95,8 +112,7 @@ func (n *networkRouter) getNetwork(ctx context.Context, w http.ResponseWriter, r
 	)
 	if v := r.URL.Query().Get("verbose"); v != "" {
 		if verbose, err = strconv.ParseBool(v); err != nil {
-			err = fmt.Errorf("invalid value for verbose: %s", v)
-			return errors.NewBadRequestError(err)
+			return errors.Wrapf(invalidRequestError{err}, "invalid value for verbose: %s", v)
 		}
 	}
 	scope := r.URL.Query().Get("scope")
@@ -177,7 +193,7 @@ func (n *networkRouter) getNetwork(ctx context.Context, w http.ResponseWriter, r
 		}
 	}
 	if len(listByFullName) > 1 {
-		return fmt.Errorf("network %s is ambiguous (%d matches found based on name)", term, len(listByFullName))
+		return errors.Wrapf(ambigousResultsError(term), "%d matches found based on name", len(listByFullName))
 	}
 
 	// Find based on partial ID, returns true only if no duplicates
@@ -187,7 +203,7 @@ func (n *networkRouter) getNetwork(ctx context.Context, w http.ResponseWriter, r
 		}
 	}
 	if len(listByPartialID) > 1 {
-		return fmt.Errorf("network %s is ambiguous (%d matches found based on ID prefix)", term, len(listByPartialID))
+		return errors.Wrapf(ambigousResultsError(term), "%d matches found based on ID prefix", len(listByPartialID))
 	}
 
 	return libnetwork.ErrNoSuchNetwork(term)