HIP: Add Exclude File Option to Helm Lint Command

hips/hip-0019.md

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+--- 
+hip: 0019
+title: "Add Exclude File Option to Helm Lint Command"
+authors: Danilo Patrucco
+created: "2024-07-03"
+type: "feature"
+status: "draft"
+---
+
+## Abstract
+This proposal introduces enhancements to the `helm lint` command, allowing the exclusion of specific files or patterns through a `.helmlintconfig.yaml` file, analogous to `.gitignore` or `.helmignore`. Additionally, a `--lint-config-file` flag will be added to specify alternative locations for the `.helmlintconfig.yaml` file. This feature is particularly useful in projects with multiple sub-charts. An environment variable `HELM_LINT_CONFIG_FILE` will also be introduced to mirror the functionality of the flag.
+
+## Motivation
+In large Helm charts, certain files or configurations may not conform to standard linting rules but are accepted by the maintainers. The current `helm lint` process evaluates all files within a chart, often leading to irrelevant warnings or errors. An option to exclude specific files and the ability to specify config file locations would streamline the linting process.
+
+## Rationale
+The aim of this proposal is to grant developers and integrators more control over the linting process by enabling:
+- Exclusions for files imported or managed by third parties that are not directly editable.
+- Exclusions for files that may not adhere to static linting rules.
+- Exclusions for files containing intentional deviations from standard practices due to specific deployment scenarios.
+
+The `.helmlintconfig.yaml` file will support simple patterns for matching files and directories, enhancing ease of management. The `--lint-config-file` flag will facilitate centralized management of lint exclusions in complex projects.
+
+## Specification
+### `.helmlintconfig.yaml` File Format
+The `.helmlintconfig.yaml` file enables chart developers to specify glob patterns for both file paths and error stirngs to exclude from linting. The format is YAML, with patterns specified under a `lintConfig` key, making future extensions for additional configurations feasible.
+
+#### Example
+```
+# .helmlintconfig.yaml file example
+lintIgnore:
+  - pathIgnore: "migrations/templates/job.yaml"                                       # Ignores all errors from this file
+  - errorIgnore: "chart metadata is missing these dependencies**"                     # Ignores all icon errors
+  - pathIgnore: "gitlab/templates/shared-secrets/self-signed-cert-job.yml"
+    errorIgnore: "<include 'fullname' .>"                                             # Ignores this specific error but not other errors in the file
+```
+
+### Command Behavior
+When `helm lint` is executed, it checks for the presence of a `.helmlintconfig.yaml` file in the chart directory or at a location specified by the `--lint-config-file` flag. The command then parses this file to exclude any files or directories matching the patterns specified, including specific error lines.
+
+## Backwards Compatibility
+This proposal introduces no breaking changes. Charts without a `.helmlintconfig.yaml` file or those not using the `--lint-config-file` flag will function as before.
+
+## Security Implications
+No significant security implications are expected as the `.helmlintconfig.yaml` file is processed locally by `helm lint`, without modifying chart content or involving network activity.
+
+## How to Teach This
+Documentation for the `.helmlintconfig.yaml` file and the `--lint-config-file` flag will be integrated into the official Helm documentation under the `helm lint` section. Detailed examples and common patterns will be provided to assist new users.
+
+## Reference Implementation
+PR #[13257](https://github.com/helm/helm/pull/13257) created in the Helm/helm repository in gitlab 
+
+## Open Issues
+- Developing an Effective and User-Friendly Pattern Syntax: We are considering the design of a flexible and intuitive pattern syntax for the `.helmlintconfig.yaml` file. This syntax would ideally support rule-specific configurations and exclusions, allowing users to finely control lint behaviors on a per-rule basis.
+- In-File Annotations for Excluding Chart Sections: Exploring the possibility of in-file annotations that would let developers temporarily exclude specific sections of a chart from linting. This feature would provide granular control directly within Helm chart files.
+- Rule Naming and Configurations: Currently, Helm does not support named lint rules. Introducing named rules is a foundational step that would enable us to implement more sophisticated configuration features, such as rule-specific exclusions and settings. This would also allow users to extend or override a "default" configuration set, similar to practices seen in tools like [yamllint](https://yamllint.readthedocs.io/en/stable/configuration.html#extending-the-default-configuration). Naming rules would facilitate clearer and more maintainable configurations, laying the groundwork for future enhancements.
+- Future Enhancements and Extensibility: The proposed changes to the Helm linting system will likely require significant modifications to the existing codebase. As such, these enhancements could be implemented in phases, starting with foundational features like rule naming and extending to more complex configurations. This phased approach will help ensure stability and usability while expanding the linting capabilities of Helm.
+
+## Rejected Ideas
+None at this time.
+
+## References
+- This proposal aligns with practices outlined in [HIP-0001](https://github.com/helm/community/blob/master/hips/hip-0001.md).