job-list: return nnodes if jobspec specifies nodes

Problem: job-list does not return nnodes until a job is running.
When a job specifically requests a number of nodes, it may be
useful for job-list to return nnodes so it can be listed in
job listing tools such as flux-jobs.

Solution: If the jobspec specifically lists nodes as a requested
resource, have job-list return nnodes even before it is running.

Fixes #4530

Author: chu11

src/modules/job-list/job_state.c

@@ -397,6 +397,7 @@ static int jobspec_parse (struct list_ctx *ctx,
     json_error_t error;
     json_t *jobspec = NULL;
     json_t *tasks, *resources, *command, *jobspec_job = NULL;
+    struct res_level res[3];
     int rc = -1;
 
     if (!(jobspec = json_loads (s, 0, &error))) {
@@ -488,13 +489,33 @@ static int jobspec_parse (struct list_ctx *ctx,
         goto nonfatal_error;
     }
 
+    /* For jobspec version 1, expect either:
+     * - node->slot->core->NIL
+     * - slot->core->NIL
+     */
+    memset (res, 0, sizeof (res));
+    if (parse_res_level (ctx, job, resources, &res[0]) < 0)
+        goto nonfatal_error;
+    if (res[0].with && parse_res_level (ctx, job, res[0].with, &res[1]) < 0)
+        goto nonfatal_error;
+    if (res[1].with && parse_res_level (ctx, job, res[1].with, &res[2]) < 0)
+        goto nonfatal_error;
+
+    /* Set job->nnodes if available.  In jobspec version 1, only if
+     * resources listed as node->slot->core->NIL
+     */
+    if (res[0].type != NULL && !strcmp (res[0].type, "node")
+        && res[1].type != NULL && !strcmp (res[1].type, "slot")
+        && res[2].type != NULL && !strcmp (res[2].type, "core")
+        && res[2].with == NULL)
+        job->nnodes = res[0].count;
+
     /* Set job->ntasks
      */
     if (json_unpack_ex (tasks, NULL, 0,
                         "[{s:{s:i}}]",
                         "count", "total", &job->ntasks) < 0) {
         int per_slot, slot_count = 0;
-        struct res_level res[3];
 
         if (json_unpack_ex (tasks, &error, 0,
                             "[{s:{s:i}}]",
@@ -510,18 +531,6 @@ static int jobspec_parse (struct list_ctx *ctx,
                       __FUNCTION__, (uintmax_t)job->id, per_slot);
             goto nonfatal_error;
         }
-        /* For jobspec version 1, expect either:
-         * - node->slot->core->NIL
-         * - slot->core->NIL
-         * Set job->slot_count.
-         */
-        memset (res, 0, sizeof (res));
-        if (parse_res_level (ctx, job, resources, &res[0]) < 0)
-            goto nonfatal_error;
-        if (res[0].with && parse_res_level (ctx, job, res[0].with, &res[1]) < 0)
-            goto nonfatal_error;
-        if (res[1].with && parse_res_level (ctx, job, res[1].with, &res[2]) < 0)
-            goto nonfatal_error;
         if (res[0].type != NULL && !strcmp (res[0].type, "slot")
             && res[1].type != NULL && !strcmp (res[1].type, "core")
             && res[1].with == NULL) {

src/modules/job-list/job_util.c

@@ -91,9 +91,9 @@ static int store_attr (struct job *job,
         val = json_integer (job->ntasks);
     }
     else if (!strcmp (attr, "nnodes")) {
-        /* job->nnodes potentially < 0 if R invalid */
-        if (!(job->states_mask & FLUX_JOB_STATE_RUN)
-            || job->nnodes < 0)
+        /* job->nnodes < 0 if not set yet or R invalid, may be set in
+         * DEPEND or RUN state */
+        if (job->nnodes < 0)
             return 0;
         val = json_integer (job->nnodes);
     }