Add warning: If component has update() but no verify()

CHANGES.md

@@ -16,6 +16,8 @@
   context. This variable contains a comment block that signals that
   the file content is generated by batou. (#356)
 - Development: update Sphinx to 5.3.0 to fix readthedocs build failures.
+- Component object model: Class variable .instances renamed to ._instances
+  to avoid collisions with user-applications.
 
 ## 2.5.0b3 (2024-08-05)
 -----------------------

src/batou/__init__.py

@@ -521,6 +521,43 @@ def report(self):
         output.tabular("Root", self.root_name, red=True)
 
 
+class ComponentWithUpdateWithoutVerify(ConfigurationError):
+    """Some components have an update method but no verify method."""
+
+    sort_key = (5, "without_verify")
+
+    @classmethod
+    def from_context(cls, components, roots):
+        self = cls()
+        self.components = []
+        for component in components:
+            self.components.append(repr(component.__class__.__name__))
+        self.roots = []
+        for root in roots:
+            self.roots.append(root.name)
+        return self
+
+    def __str__(self):
+        out_str = "Some components have an update method but no verify method:"
+        for idx, component in enumerate(self.components):
+            out_str += f"\n    {component}"
+            out_str += f"\nRoot: {self.roots[idx]}"
+        out_str += f"\nThe update() method may not be called by batou if the verify() method is missing."
+        return out_str
+
+    def report(self):
+        output.error(
+            f"Some components have an update method but no verify method:"
+        )
+        for component in self.components:
+            output.line(f"    {component}", red=True)
+        output.tabular("Root", self.root_name, red=True)
+        output.line(
+            f"The update() method may not be called by batou if the verify() method is missing.",
+            red=True,
+        )
+
+
 class UnsatisfiedResources(ConfigurationError):
     """Some required resources were never provided."""
 

src/batou/component.py

@@ -159,7 +159,7 @@ class Component(object):
     #: After the configuration phase, this list is checked for
     #: components that have component._prepared == False and
     #: warns about them.
-    instances: List["Component"] = []
+    _instances: List["Component"] = []
 
     @property
     def defdir(self):
@@ -229,7 +229,7 @@ def __init__(self, namevar=None, **kw):
 
         self._init_breadcrumbs = init_breadcrumbs
 
-        Component.instances.append(self)
+        Component._instances.append(self)
         self.timer = batou.utils.Timer(self.__class__.__name__)
         # Are any keyword arguments undefined attributes?
         # This is a somewhat rough implementation as it allows overriding

src/batou/environment.py

@@ -15,6 +15,7 @@
 import batou.vfs
 from batou import (
     ComponentLoadingError,
+    ComponentWithUpdateWithoutVerify,
     ConfigurationError,
     CycleErrorDetected,
     DuplicateHostError,
@@ -492,13 +493,14 @@ def configure(self):
 
         while working_set:
             exceptions = []
+            components_without_verify = []
             previous_working_sets.append(working_set.copy())
             retry = set()
             self.resources.dirty_dependencies.clear()
 
             for root in working_set:
                 try:
-                    Component.instances.clear()
+                    Component._instances.clear()
                     self.resources.reset_component_resources(root)
                     root.overrides = self.overrides.get(root.name, {})
                     root.prepare()
@@ -518,8 +520,10 @@ def configure(self):
                         )
                     )
                 else:
+                    # warnings: does not fail the deployment
+                    # 1. unprepared component warning
                     unprepared_components = []
-                    for component in Component.instances:
+                    for component in Component._instances:
                         if not component._prepared:
                             unprepared_components.append(component)
                     if unprepared_components:
@@ -531,6 +535,21 @@ def configure(self):
                         )
                         # exceptions.append(unused_exception)
                         output.warn(str(unused_exception))
+
+                    # 2. a component has .update() but no .verify()
+                    def has_original_update_method(component):
+                        return type(component).update == Component.update
+
+                    def has_original_verify_method(component):
+                        return type(component).verify == Component.verify
+
+                    for component in Component._instances:
+                        if (
+                            not has_original_update_method(component)
+                            and has_original_verify_method(component)
+                            and (component not in components_without_verify)
+                        ):
+                            components_without_verify.append((component, root))
                     # configured this component successfully
                     # we won't have to retry it later
                     continue
@@ -573,6 +592,15 @@ def configure(self):
 
             working_set = retry
 
+        # warn if a component has .update() but no .verify()
+        if components_without_verify:
+            component_without_verify_exception = (
+                ComponentWithUpdateWithoutVerify.from_context(
+                    components_without_verify, root
+                )
+            )
+            output.warn(str(component_without_verify_exception))
+
         # We managed to converge on a working set. However, some resource were
         # provided but never used. We're rather picky here and report this as
         # an error.