feat(cli): add copier schema command to generate JSON Schema for copier.yml

README.md

@@ -85,6 +85,8 @@ To generate a project from the template:
     copier copy path/to/project/template path/to/destination
     ```
 
+    Generate a JSON Schema for your `copier.yml` with `copier schema`.
+
 - Or in Python code, programmatically:
 
     ```python

copier/_cli.py

@@ -1,6 +1,6 @@
 """Command line entrypoint. This module declares the Copier CLI applications.
 
-Basically, there are 4 different commands you can run:
+Basically, there are 5 different commands you can run:
 
 -   `copier`, the main app, which is a shortcut for the
     `copy` and `update` subapps.
@@ -48,6 +48,15 @@
         copier check-update
         ```
 
+-   `copier schema` to generate a JSON Schema for
+    `copier.yml` files.
+
+    !!! example
+
+        ```sh
+        copier schema -o copier.schema.json
+        ```
+
 Below are the docs of each one of those.
 
 CLI help generated from `copier --help-all`:
@@ -565,3 +574,35 @@ def inner() -> int:
             return 0
 
         return _handle_exceptions(inner)
+
+
+@CopierApp.subcommand("schema")
+class CopierSchemaSubApp(cli.Application):
+    """The `copier schema` subcommand.
+
+    Use this subcommand to generate a JSON Schema for copier.yml files.
+    The schema can be used by IDEs for autocompletion, hints, and validation.
+    """
+
+    DESCRIPTION = "Generate a JSON Schema for copier.yml files"
+
+    output = cli.SwitchAttr(
+        ["-o", "--output"],
+        help="Write the schema to a file path instead of stdout.",
+    )
+
+    def main(self) -> int:
+        """Generate and output the JSON Schema."""
+
+        def inner() -> None:
+            from ._schema import generate_copier_yml_schema
+
+            schema = generate_copier_yml_schema()
+            text = json.dumps(schema, indent=2) + "\n"
+
+            if self.output:
+                Path(self.output).write_text(text)
+            else:
+                print(text)
+
+        return _handle_exceptions(inner)