Version exec json check.

Keep backwards compatibility with old versions of the api.

Signed-off-by: David Calavera <david.calavera@gmail.com>

api/server/router/local/exec.go

@@ -60,9 +60,14 @@ func (s *router) postContainerExecStart(ctx context.Context, w http.ResponseWrit
 	if err := httputils.ParseForm(r); err != nil {
 		return err
 	}
-	if err := httputils.CheckForJSON(r); err != nil {
-		return err
+
+	version := httputils.VersionFromContext(ctx)
+	if version.GreaterThan("1.21") {
+		if err := httputils.CheckForJSON(r); err != nil {
+			return err
+		}
 	}
+
 	var (
 		execName                  = vars["name"]
 		stdin, inStream           io.ReadCloser

integration-cli/docker_api_exec_test.go

@@ -52,29 +52,20 @@ func (s *DockerSuite) TestExecApiCreateNoValidContentType(c *check.C) {
 func (s *DockerSuite) TestExecAPIStart(c *check.C) {
 	dockerCmd(c, "run", "-d", "--name", "test", "busybox", "top")
 
-	createExec := func() string {
-		_, b, err := sockRequest("POST", fmt.Sprintf("/containers/%s/exec", "test"), map[string]interface{}{"Cmd": []string{"true"}})
-		c.Assert(err, check.IsNil, check.Commentf(string(b)))
-
-		createResp := struct {
-			ID string `json:"Id"`
-		}{}
-		c.Assert(json.Unmarshal(b, &createResp), check.IsNil, check.Commentf(string(b)))
-		return createResp.ID
-	}
-
 	startExec := func(id string, code int) {
 		resp, body, err := sockRequestRaw("POST", fmt.Sprintf("/exec/%s/start", id), strings.NewReader(`{"Detach": true}`), "application/json")
 		c.Assert(err, check.IsNil)
 
 		b, err := readBody(body)
-		c.Assert(err, check.IsNil, check.Commentf(string(b)))
-		c.Assert(resp.StatusCode, check.Equals, code, check.Commentf(string(b)))
+		comment := check.Commentf("response body: %s", b)
+		c.Assert(err, check.IsNil, comment)
+		c.Assert(resp.StatusCode, check.Equals, code, comment)
 	}
 
-	startExec(createExec(), http.StatusOK)
+	id := createExec(c, "test")
+	startExec(id, http.StatusOK)
 
-	id := createExec()
+	id = createExec(c, "test")
 	dockerCmd(c, "stop", "test")
 
 	startExec(id, http.StatusNotFound)
@@ -83,9 +74,33 @@ func (s *DockerSuite) TestExecAPIStart(c *check.C) {
 	startExec(id, http.StatusNotFound)
 
 	// make sure exec is created before pausing
-	id = createExec()
+	id = createExec(c, "test")
 	dockerCmd(c, "pause", "test")
 	startExec(id, http.StatusConflict)
 	dockerCmd(c, "unpause", "test")
 	startExec(id, http.StatusOK)
 }
+
+func (s *DockerSuite) TestExecAPIStartBackwardsCompatible(c *check.C) {
+	dockerCmd(c, "run", "-d", "--name", "test", "busybox", "top")
+	id := createExec(c, "test")
+
+	resp, body, err := sockRequestRaw("POST", fmt.Sprintf("/v1.20/exec/%s/start", id), strings.NewReader(`{"Detach": true}`), "text/plain")
+	c.Assert(err, check.IsNil)
+
+	b, err := readBody(body)
+	comment := check.Commentf("response body: %s", b)
+	c.Assert(err, check.IsNil, comment)
+	c.Assert(resp.StatusCode, check.Equals, http.StatusOK, comment)
+}
+
+func createExec(c *check.C, name string) string {
+	_, b, err := sockRequest("POST", fmt.Sprintf("/containers/%s/exec", name), map[string]interface{}{"Cmd": []string{"true"}})
+	c.Assert(err, check.IsNil, check.Commentf(string(b)))
+
+	createResp := struct {
+		ID string `json:"Id"`
+	}{}
+	c.Assert(json.Unmarshal(b, &createResp), check.IsNil, check.Commentf(string(b)))
+	return createResp.ID
+}