fix(apiserver): restart copies the named job, not the first stored one (bug-1898)

RestartJobByID looked the job up with a job_id CompCondition, which the
store never evaluates, and restarted jqueryReply[0] -- the first stored
job -- for any ID, including unknown ones. It now parses the ID with
ParseIdentitySelection, fetches the rows by key and matches them with
foundJob, as ControlJobByID does: an ordinary job or <array-id>[k] is
restarted, an unknown job or element is not found, and a bare array
identity (several elements) is refused. Restart goes through the
generateJobID/submitJob seams so the handler fixture can test it.

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

src/frontend/apiserver/controllers/jobs_handler_test.go

@@ -204,6 +204,7 @@ func newHandlerFixture(t *testing.T) *handlerFixture {
 	g.GET("/:jobids", jc.GetJobByIDs)
 	g.POST("/create", jc.CreateJob)
 	g.POST("/:jobids/control", jc.ControlJobByID)
+	g.POST("/:jobids/restart", jc.RestartJobByID)
 	g.POST("/control", jc.ControlJob)
 	f.router = r
 	return f
@@ -1429,3 +1430,80 @@ func TestJobHandler_QueryPagination(t *testing.T) {
 	}
 	assertIDs(t, "all pages", sortedIDs(got...), s.all())
 }
+
+// ========== Restart by identity (bug-1898) ==========
+
+// seedRestartJob seeds a DONE job with a distinctive command.
+func (f *handlerFixture) seedRestartJob(unique uint64, command string) {
+	f.t.Helper()
+	f.seedJob(models.JobInfo{
+		Unique_JobID: int64(unique),
+		JobID:        int64(backend.ExtractArrayBaseID(unique)),
+		ArrayIdx:     backend.ExtractArrayIdx(unique),
+		JobName:      "r",
+		Command:      command,
+		JobStatus:    models.JOBSTAT["DONE"],
+	})
+}
+
+func (f *handlerFixture) restart(jobids string) *httptest.ResponseRecorder {
+	f.t.Helper()
+	return f.do(http.MethodPost, "/xce/v1/jobs/"+url.PathEscape(jobids)+"/restart", map[string]interface{}{})
+}
+
+// bug-1898: RestartJobByID copied jqueryReply[0] of an unevaluated job_id
+// CompCondition -- any job, not the one named. It must restart exactly the
+// named job (ordinary job or <array-id>[k] element), report an unknown one as
+// not found, and refuse a bare array identity (several jobs).
+func TestJobHandler_RestartNamedJob(t *testing.T) {
+	f := newHandlerFixture(t)
+	arr := handlerTestArrayBase + 30<<15
+	ord := handlerTestOrdinaryBase + 31<<15
+	// decoys first, so "the first row" is never the target by accident
+	f.seedRestartJob(handlerTestOrdinaryBase+32<<15, "decoy-a")
+	f.seedRestartJob(backend.MakeElementID(arr, 1), "elem-1")
+	f.seedRestartJob(backend.MakeElementID(arr, 2), "elem-2")
+	f.seedRestartJob(ord, "ordinary")
+
+	cases := []struct {
+		name, jobids, wantCommand string
+	}{
+		{"ordinary job by decimal id", strconv.FormatUint(ord, 10), "ordinary"},
+		{"array element by <array-id>[k]", strconv.FormatUint(arr, 10) + "[2]", "elem-2"},
+	}
+	for _, c := range cases {
+		before := len(f.submitted)
+		w := f.restart(c.jobids)
+		if w.Code != http.StatusOK && w.Code != http.StatusCreated {
+			t.Errorf("%s: status %d; body %s", c.name, w.Code, w.Body.String())
+			continue
+		}
+		if len(f.submitted) != before+1 {
+			t.Errorf("%s: %d submits, want 1", c.name, len(f.submitted)-before)
+			continue
+		}
+		if got := f.submitted[before].Job.Command; got != c.wantCommand {
+			t.Errorf("%s: restarted a copy of %q, want %q", c.name, got, c.wantCommand)
+		}
+	}
+
+	// unknown job and missing element: not found, nothing submitted
+	for _, jobids := range []string{
+		strconv.FormatUint(handlerTestOrdinaryBase+40<<15, 10),
+		strconv.FormatUint(arr, 10) + "[9]",
+	} {
+		before := len(f.submitted)
+		w := f.restart(jobids)
+		if w.Code == http.StatusOK || w.Code == http.StatusCreated || len(f.submitted) != before {
+			t.Errorf("%s: status %d, %d submits; want not found and none", jobids, w.Code, len(f.submitted)-before)
+		}
+	}
+
+	// a bare array identity names several jobs: refused, nothing submitted
+	before := len(f.submitted)
+	w := f.restart(strconv.FormatUint(arr, 10))
+	if w.Code != http.StatusBadRequest || len(f.submitted) != before {
+		t.Errorf("bare array identity: status %d, %d submits; want 400 and none; body %s",
+			w.Code, len(f.submitted)-before, w.Body.String())
+	}
+}