feat: add cli tool for listing available patches

tutor/commands/config.py

@@ -154,7 +154,21 @@ def printvalue(context: Context, key: str) -> None:
     except KeyError as e:
         raise exceptions.TutorError(f"Missing configuration value: {key}") from e
 
+@click.group(
+    name="patches",
+)
+def patches_command() -> None:
+    pass
+
+@click.command(name="list", help="Print the project root")
+@click.pass_obj
+def patches_list(context: Context) -> None:
+    config = tutor_config.load(context.root)
+    renderer = env.PatchRenderer(config)
+    renderer.print_patches_locations()
 
 config_command.add_command(save)
 config_command.add_command(printroot)
 config_command.add_command(printvalue)
+config_command.add_command(patches_command)
+patches_command.add_command(patches_list)

tutor/env.py

@@ -6,6 +6,7 @@
 import typing as t
 from copy import deepcopy
 
+import click
 import jinja2
 import pkg_resources
 
@@ -214,6 +215,55 @@ def __render(self, template: jinja2.Template) -> str:
         except jinja2.exceptions.UndefinedError as e:
             raise exceptions.TutorError(f"Missing configuration value: {e.args[0]}")
 
+class PatchRenderer(Renderer):
+    """_summary_
+
+    Args:
+        Renderer (_type_): _description_
+    """
+    def render_template(self, template_name: str) -> t.Union[str, bytes]:
+        self.current_template = template_name
+        return super().render_template(template_name)
+
+    def patch(self, name: str, separator: str = "\n", suffix: str = "") -> str:
+        if not self.patches_locations.get(name):
+            self.patches_locations.update({name: [self.current_template]})
+        else:
+            self.patches_locations[name].append(self.current_template)
+
+        # Store the template's name, and replace it with the name of this patch.
+        # This handles the case where patches themselves include patches.
+        original_template = self.current_template
+        self.current_template = f"within patch: {name}"
+
+        rendered_patch = super().patch(name, separator=separator, suffix=suffix)
+        self.current_template = original_template  # Restore the template's name from before.
+        return rendered_patch
+
+    def render_all(self, *prefix: str) -> None:
+        """
+        `prefix` can be used to limit the templates to render.
+        """
+        for template_name in self.iter_templates_in(*prefix):
+            rendered = self.render_template(template_name)
+
+    def print_patches_locations(self):
+        click.echo(f"{'PATCH'.ljust(self.space)} LOCATIONS")
+        self.render_all()
+        for key, values in self.patches_locations.items():
+            n_values = 0
+            for value in values:
+                if n_values < 1:
+                    click.echo(f"{key.ljust(self.space)} {value}")
+                    n_values += 1
+                else:
+                    click.echo(f"{''.ljust(self.space)} {value}")
+
+    def __init__(self, config: t.Optional[Config] = None, space: int = 40):
+        self.space = space
+        self.patches_locations = dict()
+        super().__init__(config)
+
 
 def is_rendered(path: str) -> bool:
     """