Merge pull request #5841 from chu11/issue5827_specifier_empty_string

python: return empty string on epoch time for D conversion flag

doc/man1/flux-jobs.rst

@@ -240,7 +240,8 @@ the following conversion flags are supported by :program:`flux jobs`:
 
 **!D**
    convert a timestamp field to ISO8601 date and time (e.g. 2020-01-07T13:31:00).
-   Defaults to empty string if timestamp field does not exist.
+   Defaults to empty string if timestamp field does not exist or the timestamp
+   is 0 (i.e epoch time).
 
 **!d**
    convert a timestamp to a Python datetime object. This allows datetime

src/bindings/python/flux/util.py

@@ -462,6 +462,11 @@ def convert_field(self, value, conv):
                 else:
                     raise
         elif conv == "D":
+            # the JobInfo class initializes many timestamps to 0.0 if
+            # they are not available.  Treat epoch time as special case
+            # and just return empty string.
+            if not value:
+                return ""
             # As above, but convert to ISO 8601 date time string.
             try:
                 value = datetime.fromtimestamp(value).strftime("%FT%T")

t/flux-jobs/tests/issue#5827/description

@@ -0,0 +1 @@
+D conversion flag outputs empty string on epoch timestamp

t/flux-jobs/tests/issue#5827/format

@@ -0,0 +1 @@
+{t_run},{t_run!D}

t/flux-jobs/tests/issue#5827/input

@@ -0,0 +1 @@
+{"id": 375843192832, "userid": 1000, "urgency": 16, "priority": 0, "t_submit": 1711580059.6155457, "t_depend": 1711580059.6265068, "state": 8, "name": "sleep", "cwd": "/tmp/foo", "ntasks": 1, "ncores": 1, "duration": 0.0}

t/flux-jobs/tests/issue#5827/output

@@ -0,0 +1 @@
+0.0,