api: remove plain-text error-responses (api < v1.24)

Commit 322e2a7d05 changed the format of errors
returned by the API to be in JSON format for API v1.24. Older versions of
the API returned errors in plain-text format.

API v1.23 and older are deprecated, so we can remove support for plain-text
error responses.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/server/errorhandler.go

@@ -1,34 +0,0 @@
-package server
-
-import (
-	"net/http"
-
-	"github.com/docker/docker/api/server/httpstatus"
-	"github.com/docker/docker/api/server/httputils"
-	"github.com/docker/docker/api/types"
-	"github.com/docker/docker/api/types/versions"
-	"github.com/gorilla/mux"
-	"google.golang.org/grpc/status"
-)
-
-// makeErrorHandler makes an HTTP handler that decodes a Docker error and
-// returns it in the response.
-func makeErrorHandler(err error) http.HandlerFunc {
-	return func(w http.ResponseWriter, r *http.Request) {
-		statusCode := httpstatus.FromError(err)
-		vars := mux.Vars(r)
-		if apiVersionSupportsJSONErrors(vars["version"]) {
-			response := &types.ErrorResponse{
-				Message: err.Error(),
-			}
-			_ = httputils.WriteJSON(w, statusCode, response)
-		} else {
-			http.Error(w, status.Convert(err).Message(), statusCode)
-		}
-	}
-}
-
-func apiVersionSupportsJSONErrors(version string) bool {
-	const firstAPIVersionWithJSONErrors = "1.23"
-	return version == "" || versions.GreaterThan(version, firstAPIVersionWithJSONErrors)
-}

api/server/server.go

@@ -10,6 +10,7 @@ import (
 	"github.com/docker/docker/api/server/middleware"
 	"github.com/docker/docker/api/server/router"
 	"github.com/docker/docker/api/server/router/debug"
+	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/dockerversion"
 	"github.com/gorilla/mux"
 	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
@@ -57,19 +58,13 @@ func (s *Server) makeHTTPHandler(handler httputils.APIFunc, operation string) ht
 			if statusCode >= 500 {
 				log.G(ctx).Errorf("Handler for %s %s returned error: %v", r.Method, r.URL.Path, err)
 			}
-			makeErrorHandler(err)(w, r)
+			_ = httputils.WriteJSON(w, statusCode, &types.ErrorResponse{
+				Message: err.Error(),
+			})
 		}
 	}), operation).ServeHTTP
 }
 
-type pageNotFoundError struct{}
-
-func (pageNotFoundError) Error() string {
-	return "page not found"
-}
-
-func (pageNotFoundError) NotFound() {}
-
 // CreateMux returns a new mux with all the routers registered.
 func (s *Server) CreateMux(routers ...router.Router) *mux.Router {
 	m := mux.NewRouter()
@@ -91,7 +86,12 @@ func (s *Server) CreateMux(routers ...router.Router) *mux.Router {
 		m.Path("/debug" + r.Path()).Handler(f)
 	}
 
-	notFoundHandler := makeErrorHandler(pageNotFoundError{})
+	notFoundHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_ = httputils.WriteJSON(w, http.StatusNotFound, &types.ErrorResponse{
+			Message: "page not found",
+		})
+	})
+
 	m.HandleFunc(versionMatcher+"/{path:.*}", notFoundHandler)
 	m.NotFoundHandler = notFoundHandler
 	m.MethodNotAllowedHandler = notFoundHandler

integration-cli/docker_api_test.go

@@ -3,7 +3,6 @@ package main
 import (
 	"context"
 	"fmt"
-	"io"
 	"net/http"
 	"runtime"
 	"strconv"
@@ -62,9 +61,9 @@ func (s *DockerAPISuite) TestAPIClientVersionOldNotSupported(c *testing.T) {
 	defer body.Close()
 	assert.Equal(c, resp.StatusCode, http.StatusBadRequest)
 	expected := fmt.Sprintf("client version %s is too old. Minimum supported API version is %s, please upgrade your client to a newer version", version, testEnv.DaemonVersion.MinAPIVersion)
-	content, err := io.ReadAll(body)
+	b, err := request.ReadBody(body)
 	assert.NilError(c, err)
-	assert.Equal(c, strings.TrimSpace(string(content)), expected)
+	assert.Equal(c, getErrorMessage(c, b), expected)
 }
 
 func (s *DockerAPISuite) TestAPIErrorJSON(c *testing.T) {
@@ -77,19 +76,6 @@ func (s *DockerAPISuite) TestAPIErrorJSON(c *testing.T) {
 	assert.Equal(c, getErrorMessage(c, b), runconfig.ErrEmptyConfig.Error())
 }
 
-func (s *DockerAPISuite) TestAPIErrorPlainText(c *testing.T) {
-	// Windows requires API 1.25 or later. This test is validating a behaviour which was present
-	// in v1.23, but changed in 1.24, hence not applicable on Windows. See apiVersionSupportsJSONErrors
-	testRequires(c, DaemonIsLinux)
-	httpResp, body, err := request.Post(testutil.GetContext(c), "/v1.23/containers/create", request.JSONBody(struct{}{}))
-	assert.NilError(c, err)
-	assert.Equal(c, httpResp.StatusCode, http.StatusBadRequest)
-	assert.Assert(c, strings.Contains(httpResp.Header.Get("Content-Type"), "text/plain"))
-	b, err := request.ReadBody(body)
-	assert.NilError(c, err)
-	assert.Equal(c, strings.TrimSpace(string(b)), runconfig.ErrEmptyConfig.Error())
-}
-
 func (s *DockerAPISuite) TestAPIErrorNotFoundJSON(c *testing.T) {
 	// 404 is a different code path to normal errors, so test separately
 	httpResp, body, err := request.Get(testutil.GetContext(c), "/notfound", request.JSON)
@@ -100,13 +86,3 @@ func (s *DockerAPISuite) TestAPIErrorNotFoundJSON(c *testing.T) {
 	assert.NilError(c, err)
 	assert.Equal(c, getErrorMessage(c, b), "page not found")
 }
-
-func (s *DockerAPISuite) TestAPIErrorNotFoundPlainText(c *testing.T) {
-	httpResp, body, err := request.Get(testutil.GetContext(c), "/v1.23/notfound", request.JSON)
-	assert.NilError(c, err)
-	assert.Equal(c, httpResp.StatusCode, http.StatusNotFound)
-	assert.Assert(c, strings.Contains(httpResp.Header.Get("Content-Type"), "text/plain"))
-	b, err := request.ReadBody(body)
-	assert.NilError(c, err)
-	assert.Equal(c, strings.TrimSpace(string(b)), "page not found")
-}