Implement cli option.

Author: tobiasraabe

src/_pytask/build.py

@@ -126,6 +126,7 @@ def main(config_from_cli: dict[str, Any]) -> Session:
         "[dim]\\[default: True][/]"
     ),
 )
+@click.option("--dry-run", type=bool, is_flag=True, help="Perform a dry-run.")
 def build(**config_from_cli: Any) -> NoReturn:
     """Collect tasks, execute them and report the results.
 

src/_pytask/config.py

@@ -246,6 +246,8 @@ def pytask_parse_config(
         config_from_file.get("sort_table", True)
     )
 
+    config["dry_run"] = config_from_cli.get("dry_run", False)
+
 
 @hookimpl
 def pytask_post_parse(config: dict[str, Any]) -> None:

tests/test_execute.py

@@ -349,3 +349,14 @@ def task_second(): pass
     assert ("Task task_example.py::task_second failed" in result.output) is (
         verbose == 2
     )
+
+
+@pytest.mark.end_to_end
+def test_dry_run(runner, tmp_path):
+    tmp_path.joinpath("task_example.py").write_text("def task_example(): ...")
+
+    result = runner.invoke(cli, ["--dry-run", tmp_path.as_posix()])
+
+    print(result.output)
+    assert result.exit_code == ExitCode.OK
+    assert "1  Would be executed" in result.output