Fix tool show-config, fixes #2702

docs/changes/2703.bugfix.rst

@@ -0,0 +1,5 @@
+Fix ``Tool`` not exposing all options defined by ``traitlets.Application``
+by default.
+
+Fix ``--show-config`` and ``--show-config-json`` by not running ``setup`` and
+``finish`` steps in case those options are given.

src/ctapipe/core/tests/test_tool.py

@@ -79,6 +79,23 @@ class MyTool(Tool):
         assert not tool.provenance_log.exists()
 
 
+def test_show_config(tmpdir, capsys):
+    """check --show-config and --show-config-json work"""
+    from ctapipe.core.tool import run_tool
+
+    class MyTool(Tool):
+        description = "test"
+        userparam = Float(5.0, help="parameter").tag(config=True)
+
+    tool = MyTool()
+
+    for o in ["--show-config", "--show-config-json"]:
+        assert run_tool(tool, [o, "--MyTool.userparam=3.1415926"], cwd=tmpdir) == 0
+        captured = capsys.readouterr()
+        assert "userparam" in captured.out
+        assert "3.1415926" in captured.out
+
+
 def test_export_config_to_yaml():
     """test that we can export a Tool's config to YAML"""
     import yaml

src/ctapipe/core/tool.py

@@ -202,17 +202,20 @@ def __init__(self, **kwargs):
         # makes sure user defined aliases override default aliases
         self.aliases = {**aliases, **self.aliases}
 
-        flags = {
-            ("q", "quiet"): ({"Tool": {"quiet": True}}, "Disable console logging."),
-            ("v", "verbose"): (
-                {"Tool": {"log_level": "DEBUG"}},
-                "Set log level to DEBUG",
-            ),
-            "overwrite": (
-                {"Tool": {"overwrite": True}},
-                "Overwrite existing output files without asking",
-            ),
-        }
+        flags = Application.flags.copy()
+        flags.update(
+            {
+                ("q", "quiet"): ({"Tool": {"quiet": True}}, "Disable console logging."),
+                ("v", "verbose"): (
+                    {"Tool": {"log_level": "DEBUG"}},
+                    "Set log level to DEBUG",
+                ),
+                "overwrite": (
+                    {"Tool": {"overwrite": True}},
+                    "Overwrite existing output files without asking",
+                ),
+            }
+        )
         self.flags = {**flags, **self.flags}
 
         self.is_setup = False
@@ -423,8 +426,9 @@ def run(self, argv=None, raises=False):
 
                 self.initialize(argv)
 
-                self.setup()
-                self.is_setup = True
+                if not self.show_config:
+                    self.setup()
+                    self.is_setup = True
 
                 self.log.debug("CONFIG: %s", self.get_current_config())
                 Provenance().add_config(self.get_current_config())
@@ -437,7 +441,9 @@ def run(self, argv=None, raises=False):
                 self.log.removeHandler(self.trait_warning_handler)
 
                 self.start()
-                self.finish()
+                if not self.show_config:
+                    self.finish()
+
             except (ToolConfigurationError, TraitError) as err:
                 current_exception = err
                 self.log.error("%s", err)