Allow hook to be string of Step instance

src/stpipe/hooks.py

@@ -1,6 +1,7 @@
 """
 Pre- and post-hooks
 """
+import ast
 import inspect
 
 from . import function_wrapper, utilities
@@ -40,6 +41,18 @@ def hook_from_string_or_class(step, hooktype, num, command):
         except ImportError:
             # String is possibly a subproc, so handle this later
             pass
+        except AttributeError:
+            # String points to an instance of a Step
+            # So import the class
+            class_string, _, params = command.partition("(")
+            step_class = utilities.import_class(
+                class_string, subclassof=Step, config_file=step.config_file
+            )
+            # Then convert rest of string to args and instantiate the class
+            kwargs_string = params.strip(")")
+            expr = ast.parse(f"dict({kwargs_string}\n)", mode="eval")
+            kwargs = {kw.arg: ast.literal_eval(kw.value) for kw in expr.body.keywords}
+            return step_class(**kwargs)
         except TypeError:
             # String points to a function
             step_func = utilities.import_func(command)

src/stpipe/step.py

@@ -447,7 +447,6 @@ def run(self, *args):
                     hook_results = pre_hook.run(*hook_args)
                     if hook_results is not None:
                         hook_args = hook_results
-                self.log.info("hook_args: %s", hook_args)
                 args = hook_args
 
                 self._reference_files_used = []

tests/test_hooks.py

@@ -21,6 +21,20 @@ def process(self, input_data):
         return input_data
 
 
+class HookStep(Step):
+    class_alias = "myhook"
+
+    spec = """
+    param1 = string(default="bar")
+    param2 = float(default=1)
+    """
+
+    def process(self, input_data):
+        self.log.info("Running HookStep with %s and %s", self.param1, self.param2)
+
+        return input_data
+
+
 class MyPipeline(Pipeline):
     class_alias = "mypipeline"
 
@@ -36,20 +50,6 @@ def process(self, input_data):
         return result  # noqa: RET504
 
 
-class HookStep(Step):
-    class_alias = "myhook"
-
-    spec = """
-    param1 = string(default="bar")
-    param2 = float(default=1)
-    """
-
-    def process(self, input_data):
-        self.log.info("Running HookStep with %s and %s", self.param1, self.param2)
-
-        return input_data
-
-
 def hook_function(input_data):
     import logging
 
@@ -71,7 +71,6 @@ def test_hook_as_step_class(caplog):
             ]
         }
     }
-
     MyPipeline.call(model, steps=steps)
 
     assert "Running HookStep with bar and 1" in caplog.text
@@ -90,7 +89,6 @@ def test_hook_as_step_instance(caplog):
             ]
         }
     }
-
     MyPipeline.call(model, steps=steps)
 
     assert "Running HookStep with foo and 3" in caplog.text
@@ -108,12 +106,28 @@ def test_hook_as_string_of_importable_step_class(caplog):
             ]
         }
     }
-
     MyPipeline.call(model, steps=steps)
 
     assert "Running HookStep" in caplog.text
 
 
+def test_hook_as_string_of_step_instance(caplog):
+    """Test a string of a fully-qualified Step instance w/params"""
+    datamodels = pytest.importorskip("stdatamodels.jwst.datamodels")
+    model = datamodels.ImageModel((10, 10))
+
+    steps = {
+        "shovelpixels": {
+            "post_hooks": [
+                "test_hooks.HookStep(param1='foo', param2=2)",
+            ]
+        }
+    }
+    MyPipeline.call(model, steps=steps)
+
+    assert "Running HookStep with foo and 2" in caplog.text
+
+
 def test_hook_as_string_of_importable_function(caplog):
     """Test a string of a fully-qualified function path can be a hook"""
     datamodels = pytest.importorskip("stdatamodels.jwst.datamodels")
@@ -126,13 +140,12 @@ def test_hook_as_string_of_importable_function(caplog):
             ]
         }
     }
-
     MyPipeline.call(model, steps=steps)
 
     assert "Running hook_function on data array of size (10, 10)" in caplog.text
 
 
-def test_hook_as_subproccess(caplog, tmp_cwd):
+def test_hook_as_systemcall(caplog, tmp_cwd):
     """Test a string of a terminal command"""
     datamodels = pytest.importorskip("stdatamodels.jwst.datamodels")
     model = datamodels.ImageModel((10, 10))
@@ -149,13 +162,11 @@ def test_hook_as_subproccess(caplog, tmp_cwd):
             ]
         }
     }
-
     MyPipeline.call(model, steps=steps)
 
     # Logs from fitsinfo
-    assert "shovelpixels.post_hook0" in caplog.text
     assert "SystemCall instance created" in caplog.text
-    assert f"hook_args: (<ImageModel(10, 10) from {filename}>,)" in caplog.text
+    assert "Spawning 'fitsinfo stpipe.MyPipeline.shovelpixels.post_hook0" in caplog.text
 
     # logs from fitsheader
     assert "DATAMODL= 'ImageModel'" in caplog.text