Script to add new rule file

.gitignore

@@ -18,3 +18,4 @@ build/
 docs/source/rules/
 coverage.xml
 coverage_report.html
+.idea/

docs/source/build_a_lint_rule.ipynb

@@ -121,14 +121,86 @@
     "        ..."
    ]
   },
+  {
+   "cell_type": "raw",
+   "metadata": {},
+   "source": [
+    "Iteration order of attributes is the same as the order they appear in the source code.\n",
+    "In this case, that means visit_If_test is called before visit_If_body and visit_If_orelse.\n",
+    "\n",
+    "Use fixit's cli to generate a skeleton of new rule file::\n",
+    "\n",
+    "    $ python -m fixit.cli.add_new_rule # Creates new_rule.py at fixit/rules/new_rule.py\n",
+    "    $ python -m fixit.cli.add_new_rule --path fixit/rules/my_rule.py # Creates rule file at path specified\n",
+    "\n",
+    "This will generate a model rule file used to create new rule."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "outputs": [],
+   "source": [
+    "import libcst as cst\n",
+    "import libcst.matchers as m\n",
+    "\n",
+    "from fixit import CstLintRule, InvalidTestCase as Invalid, ValidTestCase as Valid\n",
+    "\n",
+    "class Rule(CstLintRule):\n",
+    "    \"\"\"\n",
+    "    docstring or new_rule description\n",
+    "    \"\"\"\n",
+    "\n",
+    "    MESSAGE = \"Enter rule description message\"\n",
+    "\n",
+    "    VALID = [Valid(\"'example'\")]     # Valid examples\n",
+    "\n",
+    "    INVALID = [Invalid(\"'example'\")] # Invalid examples\n",
+    "    ..."
+   ],
+   "metadata": {
+    "collapsed": false,
+    "pycharm": {
+     "name": "#%%\n"
+    }
+   }
+  },
+  {
+   "cell_type": "raw",
+   "source": [
+    "Use above structure to create a new rule. \n",
+    "\n",
+    "The Declarative Matcher API\n",
+    "===========================\n",
+    "\n",
+    "Once we have a ``ClassDef`` node, we need to see if it contains a base class named ``object``.\n",
+    "We could implement by inspecting attributes of the node using equality and isinstance."
+   ],
+   "metadata": {
+    "collapsed": false
+   }
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# check if any of the base classes of this class def is \"object\"\n",
+    "def visit_ClassDef(self, node: cst.ClassDef):\n",
+    "    has_object_base = any(\n",
+    "        isinstance(arg.value, cst.Name) and arg.value.value == \"object\"\n",
+    "        for arg in node.bases\n",
+    "    )"
+   ]
+  },
   {
    "cell_type": "raw",
    "metadata": {
     "raw_mimetype": "text/restructuredtext"
    },
    "source": [
-    "Iteration order of attributes is the same as the order they appear in the source code.\n",
-    "In this case, that means visit_If_test is called before visit_If_body and visit_If_orelse.\n",
+    "Use above structure to create a new rule. \n",
     "\n",
     "The Declarative Matcher API\n",
     "===========================\n",
@@ -323,9 +395,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.5"
+   "version": "3.7.0b1"
   }
  },
  "nbformat": 4,
  "nbformat_minor": 4
-}
+}

fixit/cli/add_new_rule.py

@@ -0,0 +1,95 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+# Usage:
+#
+#   $ python -m fixit.cli.add_new_rule --help
+#   $ python -m fixit.cli.add_new_rule
+#   $ python -m fixit.cli.add_new_rule --path fixit/rules/new_rule.py
+
+import argparse
+from pathlib import Path
+
+from libcst.codemod._cli import invoke_formatter
+
+from fixit.common.config import get_lint_config
+
+
+_LICENCE = """# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+"""
+
+_IMPORTS = """
+import libcst as cst
+import libcst.matchers as m
+
+from fixit import CstLintRule, InvalidTestCase as Invalid, ValidTestCase as Valid
+
+"""
+
+_TO_DOS = """
+\"""
+This is a model rule file for adding a new rule to fixit module
+\"""
+
+"""
+
+_RULE_CLASS = """
+class Rule(CstLintRule):
+    \"""
+    docstring or new_rule description
+    \"""
+
+    MESSAGE = "Enter rule description message"
+
+    VALID = [Valid("'example'")]
+
+    INVALID = [Invalid("'example'")]
+"""
+
+
+def is_path_exists(path: str) -> Path:
+    """Check for valid path, if yes, return `Path` else raise `Error` """
+    filepath = Path(path)
+    if filepath.exists():
+        raise FileNotFoundError(f"{filepath} already exists")
+    elif not filepath.parent.exists():
+        raise TypeError(f"{filepath} is not a valid path, provide path with file name")
+    else:
+        return filepath
+
+
+def create_rule_file(file_path: Path) -> None:
+    """Create a new rule file."""
+    context = _LICENCE + _IMPORTS + _TO_DOS + _RULE_CLASS
+    updated_context = invoke_formatter(get_lint_config().formatter, context)
+
+    with open(file_path, "w") as f:
+        f.write(updated_context)
+
+    print(f"Successfully created {file_path.name} rule file at {file_path.parent}")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(
+        description="Creates a skeleton of adding new rule file"
+    )
+    parser.add_argument(
+        "-p",
+        "--path",
+        type=is_path_exists,
+        default=Path("fixit/rules/new_rule.py"),
+        help="Path to add rule file, Default is fixit/rules/new_rule.py",
+    )
+
+    args = parser.parse_args()
+    create_rule_file(args.path)
+
+
+if __name__ == "__main__":
+    main()