[Gemini Code Assist on GitHub](https://docs.cloud.google.com/gemini/docs/code-review/review-repo-code.md.txt) lets you define custom conventions and best practices to use when performing automated code reviews. You can apply a style guide directly to an individual repository by adding a `styleguide.md` Markdown file to the `.gemini/` root folder of your repository, or [you can use the Google Cloud console](https://docs.cloud.google.com/gemini/docs/code-review/style-guide.md.txt#bulk-config) to manage standards across multiple repositories. ## Standard code review patterns When custom style guides aren't specified, these are the main categories of areas where Gemini Code Assist focuses its code review on: - **Correctness**: Makes sure the code functions as intended and handles edge cases, checks for logic errors, race conditions, or incorrect API usage. - **Efficiency**: Identifies potential performance bottlenecks or areas for optimization, like excessive loops, memory leaks, inefficient data structures, redundant calculations, excessive logging, and inefficient string manipulation. - **Maintainability**: Assesses code readability, modularity, and adherence to language idioms and best practices. Targets poor naming for variables, functions, and classes, lack of comments or documentation, complex code, code duplication, inconsistent formatting, and magic numbers. - **Security**: Identifies potential vulnerabilities in data handling or input validation, like insecure storage of sensitive data, injection attacks, insufficient access controls, Cross-Site Request Forgery (CSRF), and Insecure Direct Object References (IDOR). - **Miscellaneous**: Other topics are considered when reviewing the pull request, like testing, performance, scalability, modularity and reusability, and error logging and monitoring. ### Example style guide The `styleguide.md` file does not have a defined schema. Instead, it's a natural language description of how you want Gemini Code Assist to structure its code reviews, and it expands the standard prompt that Gemini Code Assist on GitHub uses. The following code snippet is an example of a `styleguide.md` file: # Company X Python Style Guide ## Introduction This style guide outlines the coding conventions for Python code developed at Company X. It's based on PEP 8, but with some modifications to address specific needs and preferences within our organization. ## Key Principles * **Readability:** Code should be easy to understand for all team members. * **Maintainability:** Code should be easy to modify and extend. * **Consistency:** Adhering to a consistent style across all projects improves collaboration and reduces errors. * **Performance:** While readability is paramount, code should be efficient. ## Deviations from PEP 8 ### Line Length * **Maximum line length:** 100 characters (instead of PEP 8's 79). * Modern screens allow for wider lines, improving code readability in many cases. * Many common patterns in our codebase, like long strings or URLs, often exceed 79 characters. ### Indentation * **Use 4 spaces per indentation level.** (PEP 8 recommendation) ### Imports * **Group imports:** * Standard library imports * Related third party imports * Local application/library specific imports * **Absolute imports:** Always use absolute imports for clarity. * **Import order within groups:** Sort alphabetically. ### Naming Conventions * **Variables:** Use lowercase with underscores (snake_case): `user_name`, `total_count` * **Constants:** Use uppercase with underscores: `MAX_VALUE`, `DATABASE_NAME` * **Functions:** Use lowercase with underscores (snake_case): `calculate_total()`, `process_data()` * **Classes:** Use CapWords (CamelCase): `UserManager`, `PaymentProcessor` * **Modules:** Use lowercase with underscores (snake_case): `user_utils`, `payment_gateway` ### Docstrings * **Use triple double quotes (`"""Docstring goes here."""`) for all docstrings.** * **First line:** Concise summary of the object's purpose. * **For complex functions/classes:** Include detailed descriptions of parameters, return values, attributes, and exceptions. * **Use Google style docstrings:** This helps with automated documentation generation. ```python def my_function(param1, param2): """Single-line summary. More detailed description, if necessary. Args: param1 (int): The first parameter. param2 (str): The second parameter. Returns: bool: The return value. True for success, False otherwise. Raises: ValueError: If `param2` is invalid. """ # function body here ``` ### Type Hints * **Use type hints:** Type hints improve code readability and help catch errors early. * **Follow PEP 484:** Use the standard type hinting syntax. ### Comments * **Write clear and concise comments:** Explain the "why" behind the code, not just the "what". * **Comment sparingly:** Well-written code should be self-documenting where possible. * **Use complete sentences:** Start comments with a capital letter and use proper punctuation. ### Logging * **Use a standard logging framework:** Company X uses the built-in `logging` module. * **Log at appropriate levels:** DEBUG, INFO, WARNING, ERROR, CRITICAL * **Provide context:** Include relevant information in log messages to aid debugging. ### Error Handling * **Use specific exceptions:** Avoid using broad exceptions like `Exception`. * **Handle exceptions gracefully:** Provide informative error messages and avoid crashing the program. * **Use `try...except` blocks:** Isolate code that might raise exceptions. ## Tooling * **Code formatter:** [Specify formatter, e.g., Black] - Enforces consistent formatting automatically. * **Linter:** [Specify linter, e.g., Flake8, Pylint] - Identifies potential issues and style violations. ## Manage style guides across multiple repositories You can have one style guide apply to multiple repositories. Repositories are grouped by a [Developer Connect connection](https://docs.cloud.google.com/gemini/docs/code-review/review-repo-code.md.txt#considerations), and managing their collective style guide is accomplished through the Google Cloud console. If a repository is managed as part of a group but also has its own `styleguide.md` file, the repository's `styleguide.md` is combined with the group style guide. The following steps show how you can control one style guide across multiple repositories. These steps assume you have previously [set up Gemini Code Assist on GitHub](https://docs.cloud.google.com/gemini/docs/code-review/set-up-code-assist-github.md.txt). > [!WARNING] > **Preview** > > This feature is subject to the "Pre-GA Offerings Terms" in the General > Service Terms section of the > [Service Specific Terms for Google Cloud](https://cloud.google.com/terms/service-terms#1). > Pre-GA features are available "as is" and might have limited support. For > more information, see the > [Google Cloud launch stage descriptions](https://cloud.google.com/products/#product-launch-stages). 1. In the Google Cloud console, go to the Gemini Code Assist **Agents \& Tools** page. [Go to Agents \& Tools](https://console.cloud.google.com/gemini-code-assist/agents-tools) 2. In the **Agents** section, locate the **Code Assist Source Code Management** card, and click **Advanced**. The **Edit Code Assist Source Code Management** pane opens. 3. In the **Connections** table, click the name of the connection that you want to apply a style guide to. The details page for the connection opens. 4. In the **Style guide** tab, add the style guide you want the repositories associated with this connection to use. 5. Click **Save**. ## What's next - [Modify the configuration](https://docs.cloud.google.com/gemini/docs/code-review/customize-repo-review.md.txt) for Gemini Code Assist on GitHub.