fix(apiserver): reject submit options the job never gets; add exec_home (bug-1936)

Cause: CreateJob accepted in_file, out_file, err_file, out_dir,
asked_hosts, begin_time, term_time and transfer_files and returned
success, but neither the controller's submit data/start info nor the
worker carries any of them (the worker never stages transferred files),
so they were silently dropped. Exec home had no submit field at all, and
a relative cwd would have been resolved against the worker unit's
directory.

Fix: new preCheckSubmitOptions() runs right after binding, before file
uploads and ID allocation, and answers 400 naming every unsupported
option that is set; cwd and the new exec_home field must be absolute and
fit the worker's job_assignment_t buffers (1023 bytes). exec_home goes
to JobInfo.ExecHome and from there (submitStartInfo) to the start info's
exechome. num_files already reaches exdata as nofile_limit; a handler
test now pins it. The array %J/%I submit-time substitution test (9.4)
checks cwd instead of out_file/err_file, which are now refused. Swagger
regenerated with `swag init -g cmd/main.go -o docs`.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/frontend/apiserver/controllers/jobs.go

@@ -1085,7 +1085,8 @@ func (j JobController) RestartJobByID(ctx *gin.Context) {
 
 // CreateJob godoc
 // @Summary Create a new job
-// @Description Submit a new job with specified requirements and parameters
+// @Description Submit a new job with specified requirements and parameters.
+// @Description in_file, out_file, err_file, out_dir, asked_hosts, begin_time, term_time and transfer_files are not supported yet and are rejected with 400; cwd and exec_home must be absolute paths.
 // @Tags jobs
 // @Accept json
 // @Produce json
@@ -1114,6 +1115,14 @@ func (j JobController) CreateJob(ctx *gin.Context) {
 		return
 	}
 
+	// bug-1936: refuse an option the job would never get, before anything
+	// (file uploads, ID allocation) happens for it.
+	if err := preCheckSubmitOptions(&req); err != nil {
+		logger.Error("Job submission rejected", zap.Error(err))
+		ReturnError(ctx, common.INVALID_PARAMS_CODE, err.Error(), nil)
+		return
+	}
+
 	// precheck the request parameter before generating the job ID
 	arraySize, isArray, err := preCheckJobRequest(&req)
 	if err != nil {
@@ -1220,6 +1229,7 @@ func (j JobController) CreateJob(ctx *gin.Context) {
 		UserPriority:       req.JobPriority,
 		DependCond:         req.DependCond,
 		CWD:                req.CWD,
+		ExecHome:           req.ExecHome, // bug-1936: exechome of the start info
 		FromHost:           req.FromHost, // bug-1676: client-asserted hostname, passed through unchanged
 		PreExecCmd:         req.PreExecCmd,
 		PostExecCmd:        req.PostExecCmd,
@@ -1281,6 +1291,62 @@ func (j JobController) CreateJob(ctx *gin.Context) {
 	ReturnSuccess(ctx, common.CREATED, common.SUCCESS_MSG, response)
 }
 
+// maxWorkerPathLen is the longest cwd or exec home the worker takes: xcecd
+// hands both to xcecd_worker in job_assignment_t's cwd/home[PATH_LENGTH]
+// (1024 bytes, src/worker/include/uv_ipc.h), NUL included.
+const maxWorkerPathLen = 1024 - 1
+
+// preCheckSubmitOptions rejects what a submission asks for but the job
+// would not get (bug-1936). The controller's submit data and start info
+// have no field for stdin/stdout/stderr paths, an output directory, asked
+// hosts or a begin/termination time, and the worker never stages
+// transferred files in or out, so each of those is refused instead of
+// being accepted and dropped. cwd and exec_home do reach the worker, which
+// runs the job there with HOME set; both must be absolute and fit its
+// buffers.
+func preCheckSubmitOptions(req *models.JobSubmitRequest) error {
+	unsupported := []struct {
+		field string
+		set   bool
+	}{
+		{"in_file", req.InFile != ""},
+		{"out_file", req.OutFile != ""},
+		{"err_file", req.ErrFile != ""},
+		{"out_dir", req.OutDir != ""},
+		{"asked_hosts", strings.TrimSpace(req.AskedHosts) != ""},
+		{"begin_time", !req.BeginTime.Time.IsZero()},
+		{"term_time", !req.TermTime.Time.IsZero()},
+		{"transfer_files", len(req.TransferFiles) > 0},
+	}
+	var names []string
+	for _, u := range unsupported {
+		if u.set {
+			names = append(names, u.field)
+		}
+	}
+	if len(names) > 0 {
+		return fmt.Errorf("job submission option(s) %s not supported: the job would not get them",
+			strings.Join(names, ", "))
+	}
+
+	for _, p := range []struct{ field, value string }{
+		{"cwd", req.CWD},
+		{"exec_home", req.ExecHome},
+	} {
+		if p.value == "" {
+			continue
+		}
+		if !strings.HasPrefix(p.value, "/") {
+			return fmt.Errorf("%s %q must be an absolute path", p.field, p.value)
+		}
+		if len(p.value) > maxWorkerPathLen {
+			return fmt.Errorf("%s is too long: %d bytes, more than the limit of %d",
+				p.field, len(p.value), maxWorkerPathLen)
+		}
+	}
+	return nil
+}
+
 func preCheckJobRestartRequest(req *models.JobRestartRequest) error {
 	logger.Debug("Enter preCheckJobRestartRequest")
 	if err := validateAskedHosts(req.AskedHosts); err != nil {