Add pre and post task lists into help output

invoke/program.py

@@ -781,6 +781,8 @@ def print_task_help(self, name: str) -> None:
         ctx = self.parser.contexts[name]
         tuples = ctx.help_tuples()
         docstring = inspect.getdoc(self.collection[name])
+        pre_tasks = self.collection[name].pre
+        post_tasks = self.collection[name].post
         header = "Usage: {} [--core-opts] {} {}[other tasks here ...]"
         opts = "[--options] " if tuples else ""
         print(header.format(self.binary, name, opts))
@@ -804,6 +806,27 @@ def print_task_help(self, name: str) -> None:
             print(self.leading_indent + "none")
             print("")
 
+        print("Pre-tasks:")
+        if pre_tasks:
+            for pre in pre_tasks:
+                print(
+                    self.leading_indent + self.collection.transform(pre.name)
+                )
+            print("")
+        else:
+            print(self.leading_indent + "none")
+            print("")
+        print("Post-tasks:")
+        if post_tasks:
+            for post in post_tasks:
+                print(
+                    self.leading_indent + self.collection.transform(post.name)
+                )
+            print("")
+        else:
+            print(self.leading_indent + "none")
+            print("")
+
     def list_tasks(self) -> None:
         # Short circuit if no tasks to show (Collection now implements bool)
         focus = self.scoped_collection

tests/_support/decorators.py

@@ -21,7 +21,7 @@ def foo2(c):
     pass
 
 
-@task
+@task(post=[foo2])
 def foo3(c):
     """Foo the other bar:
 
@@ -32,7 +32,7 @@ def foo3(c):
     pass
 
 
-@task(default=True)
+@task(default=True, pre=[foo3])
 def biz(c):
     pass
 

tests/program.py

@@ -308,6 +308,7 @@ def copying_from_task_context_does_not_set_empty_list_values(self):
             # .value = <default value> actually ends up creating a
             # list-of-lists.
             p = Program()
+
             # Set up core-args parser context with an iterable arg that hasn't
             # seen any value yet
             def filename_args():
@@ -643,6 +644,12 @@ def prints_help_for_task_only(self):
   -h STRING, --why=STRING   Motive
   -w STRING, --who=STRING   Who to punch
 
+Pre-tasks:
+  none
+
+Post-tasks:
+  none
+
 """.lstrip()
                 for flag in ["-h", "--help"]:
                     expect("-c decorators {} punch".format(flag), out=expected)
@@ -657,6 +664,12 @@ def works_for_unparameterized_tasks(self):
 Options:
   none
 
+Pre-tasks:
+  foo3
+
+Post-tasks:
+  none
+
 """.lstrip()
                 expect("-c decorators -h biz", out=expected)
 
@@ -676,6 +689,12 @@ def displays_docstrings_if_given(self):
 Options:
   none
 
+Pre-tasks:
+  none
+
+Post-tasks:
+  none
+
 """.lstrip()
                 expect("-c decorators -h foo", out=expected)
 
@@ -693,6 +712,12 @@ def dedents_correctly(self):
 Options:
   none
 
+Pre-tasks:
+  none
+
+Post-tasks:
+  none
+
 """.lstrip()
                 expect("-c decorators -h foo2", out=expected)
 
@@ -710,6 +735,12 @@ def dedents_correctly_for_alt_docstring_style(self):
 Options:
   none
 
+Pre-tasks:
+  none
+
+Post-tasks:
+  foo2
+
 """.lstrip()
                 expect("-c decorators -h foo3", out=expected)
 
@@ -726,6 +757,12 @@ def exits_after_printing(self):
   -h STRING, --why=STRING   Motive
   -w STRING, --who=STRING   Who to punch
 
+Pre-tasks:
+  none
+
+Post-tasks:
+  none
+
 """.lstrip()
                 expect("-c decorators -h punch --list", out=expected)
 
@@ -1374,6 +1411,7 @@ def env_vars_load_with_prefix(self, monkeypatch):
 
         def env_var_prefix_can_be_overridden(self, monkeypatch):
             monkeypatch.setenv("MYAPP_RUN_HIDE", "both")
+
             # This forces the execution stuff, including Executor, to run
             # NOTE: it's not really possible to rework the impl so this test is
             # cleaner - tasks require per-task/per-collection config, which can