CLI: Add the -M/--most-recent-node option

The `-M/--most-recent-node` option is added to the `status`, `show` and
`report` subcommands of `verdi process`. When specified, these commands
don't need specific process node identifiers but the most recent will
automatically be selected. This is a useful feature when users are
actively running processes one by one during testing and they usually
want to look at the last created process node.

Co-Authored-By: Sebastiaan Huber <mail@sphuber.net>

src/aiida/cmdline/commands/cmd_process.py

@@ -44,6 +44,18 @@ def default_projections():
     return CalculationQueryBuilder.default_projections
 
 
+def get_most_recent_node():
+    """Return the most recent process node.
+
+    :returns: The ``ProcessNode`` with the latest ``ctime``.
+    """
+    from aiida.orm import ProcessNode, QueryBuilder
+
+    process = QueryBuilder().append(ProcessNode, tag='n').order_by({'n': {'ctime': 'desc'}}).first(flat=True)
+    echo.echo_info(f'Most recent node matched: `{process}`.')
+    return process
+
+
 @verdi.group('process')
 def verdi_process():
     """Inspect and manage processes."""
@@ -156,11 +168,21 @@ def process_list(
 
 @verdi_process.command('show')
 @arguments.PROCESSES()
+@options.MOST_RECENT_NODE()
 @decorators.with_dbenv()
-def process_show(processes):
+def process_show(processes, most_recent_node):
     """Show details for one or multiple processes."""
     from aiida.cmdline.utils.common import get_node_info
 
+    if processes and most_recent_node:
+        raise click.BadOptionUsage(
+            'most_recent_node',
+            'cannot specify individual processes and the `-M/--most-recent-node` flag at the same time.',
+        )
+
+    if most_recent_node:
+        processes = [get_most_recent_node()]
+
     for process in processes:
         echo.echo(get_node_info(process))
 
@@ -190,6 +212,7 @@ def process_call_root(processes):
 
 @verdi_process.command('report')
 @arguments.PROCESSES()
+@options.MOST_RECENT_NODE()
 @click.option('-i', '--indent-size', type=int, default=2, help='Set the number of spaces to indent each level by.')
 @click.option(
     '-l',
@@ -202,11 +225,20 @@ def process_call_root(processes):
     '-m', '--max-depth', 'max_depth', type=int, default=None, help='Limit the number of levels to be printed.'
 )
 @decorators.with_dbenv()
-def process_report(processes, levelname, indent_size, max_depth):
+def process_report(processes, most_recent_node, levelname, indent_size, max_depth):
     """Show the log report for one or multiple processes."""
     from aiida.cmdline.utils.common import get_calcjob_report, get_process_function_report, get_workchain_report
     from aiida.orm import CalcFunctionNode, CalcJobNode, WorkChainNode, WorkFunctionNode
 
+    if processes and most_recent_node:
+        raise click.BadOptionUsage(
+            'most_recent_node',
+            'cannot specify individual processes and the `-M/--most-recent-node` flag at the same time.',
+        )
+
+    if most_recent_node:
+        processes = [get_most_recent_node()]
+
     for process in processes:
         if isinstance(process, CalcJobNode):
             echo.echo(get_calcjob_report(process))
@@ -219,15 +251,25 @@ def process_report(processes, levelname, indent_size, max_depth):
 
 
 @verdi_process.command('status')
+@options.MOST_RECENT_NODE()
 @click.option('-c', '--call-link-label', 'call_link_label', is_flag=True, help='Include the call link label if set.')
 @click.option(
     '-m', '--max-depth', 'max_depth', type=int, default=None, help='Limit the number of levels to be printed.'
 )
 @arguments.PROCESSES()
-def process_status(call_link_label, max_depth, processes):
+def process_status(call_link_label, most_recent_node, max_depth, processes):
     """Print the status of one or multiple processes."""
     from aiida.cmdline.utils.ascii_vis import format_call_graph
 
+    if processes and most_recent_node:
+        raise click.BadOptionUsage(
+            'most_recent_node',
+            'cannot specify individual processes and the `-M/--most-recent-node` flag at the same time.',
+        )
+
+    if most_recent_node:
+        processes = [get_most_recent_node()]
+
     for process in processes:
         graph = format_call_graph(process, max_depth=max_depth, call_link_label=call_link_label)
         echo.echo(graph)

src/aiida/cmdline/params/options/main.py

@@ -69,6 +69,7 @@
     'INPUT_PLUGIN',
     'LABEL',
     'LIMIT',
+    'MOST_RECENT_NODE',
     'NODE',
     'NODES',
     'NON_INTERACTIVE',
@@ -592,6 +593,13 @@ def set_log_level(_ctx, _param, value):
     help='Only include entries created before OLDER_THAN days ago.',
 )
 
+MOST_RECENT_NODE = OverridableOption(
+    '-M',
+    '--most-recent-node',
+    is_flag=True,
+    help='Select the most recently created node.',
+)
+
 ALL = OverridableOption(
     '-a',
     '--all',

tests/cmdline/commands/test_process.py

@@ -557,3 +557,41 @@ def test_process_repair_verbosity(monkeypatch, run_cli_command):
     result = run_cli_command(cmd_process.process_repair, ['-v', 'INFO'], use_subprocess=False)
     assert 'Active processes: [1, 2, 3, 4]' in result.output
     assert 'Process tasks: [1, 2]' in result.output
+
+
+@pytest.fixture
+def process_nodes():
+    """Return a list of two stored ``CalcJobNode`` instances with a finished process state."""
+    nodes = [CalcJobNode(), CalcJobNode()]
+    for node in nodes:
+        node.set_process_state(ProcessState.FINISHED)
+        node.store()
+    return nodes
+
+
+def test_process_report_most_recent_node(run_cli_command, process_nodes):
+    """Test ``verdi process report --most-recent-node``."""
+    result = run_cli_command(cmd_process.process_report, ['--most-recent-node'])
+    assert f'*** {process_nodes[0].pk}:' not in result.output
+    assert f'*** {process_nodes[1].pk}:' in result.output
+
+
+def test_process_show_most_recent_node(run_cli_command, process_nodes):
+    """Test ``verdi process show --most-recent-node``."""
+    result = run_cli_command(cmd_process.process_show, ['--most-recent-node'])
+    assert process_nodes[0].uuid not in result.output
+    assert process_nodes[1].uuid in result.output
+
+
+def test_process_status_most_recent_node(run_cli_command, process_nodes):
+    """Test ``verdi process status --most-recent-node``."""
+    result = run_cli_command(cmd_process.process_status, ['--most-recent-node'])
+    assert f'<{process_nodes[0].pk}>' not in result.output
+    assert f'<{process_nodes[1].pk}>' in result.output
+
+
+@pytest.mark.parametrize('command', (cmd_process.process_report, cmd_process.process_show, cmd_process.process_status))
+def test_process_most_recent_node_exclusive(run_cli_command, process_nodes, command):
+    """Test command raises if ``-M`` is specified as well as explicit process nodes."""
+    result = run_cli_command(command, ['-M', str(process_nodes[0].pk)], raises=True)
+    assert 'cannot specify individual processes and the `-M/--most-recent-node` flag at the same time.' in result.output