Feature Flags Age + AST-Grep Collector

✓ Guardrail ↓ Collector Stable Testing And Quality

Enforce Feature Flags Age using data collected by AST-Grep Collector. Automatically check testing and quality standards on every PR.

Guardrail: Detects feature flags that have existed longer than a configurable threshold. Feature flags should be temporary and removed once a feature is fully rolled out. Stale flags add complexity and technical debt to the codebase.

Data Source: Analyze source code using AST-based pattern matching with ast-grep. Define custom rules to detect security issues, anti-patterns, and code style violations.

Get Started View on GitHub

How AST-Grep Collector Powers This Guardrail

The AST-Grep Collector gathers metadata from your code analysis, security systems. This data flows into Lunar's Component JSON, where the Feature Flags Age guardrail evaluates it against your standards.

When enabled, this check runs automatically on every PR and in AI coding workflows, providing real-time enforcement with actionable feedback.

↓ AST-Grep Collector Gathers Data Collector

Extracts metadata from code, configs, and tool outputs

{ } Component JSON

Data centralized in structured format for evaluation

✓ Feature Flags Age Checks Guardrail

Pass/fail result with actionable feedback in PRs

Quick Start Configuration

Add both the collector and policy to your lunar-config.yml to enable this guardrail.

📄 lunar-config.yml

# Step 1: Enable the AST-Grep Collector
collectors:
  - uses: github://earthly/lunar-lib/collectors/ast-grep@v1.0.0
    # with: ...

# Step 2: Enable the Feature Flags Guardrails
policies:
  - uses: github://earthly/lunar-lib/policies/feature-flags@v1.0.0
    include: [feature-flags-age]
    # with: ...

What AST-Grep Collector Collects

This collector gathers the following data that the Feature Flags Age guardrail evaluates.

Collector code

`ast-grep`

Runs user-defined ast-grep YAML rules against source code and collects pattern matches. Supports full ast-grep rule syntax including relational rules (inside, has), composite rules (all, any, not), and metavariables ($VAR, $$$ARGS). Groups results by rule ID (format: category.subcategory) and writes structured matches with file, range, and code snippet to .code_patterns...

Example Data Flow

Here's an example of the data that AST-Grep Collector writes to the Component JSON, which Feature Flags Age then evaluates.

{ } component.json From AST-Grep Collector

{
  "code_patterns": {
    "source": {
      "tool": "ast-grep",
      "version": "0.40.5"
    },
    "security": {
      "sql_concat": {
        "count": 0,
        "message": "SQL query built via string concatenation",
        "severity": "error",
        "matches": []
      },
      "eval": {
        "count": 2,
        "message": "Dangerous eval() usage",
        "severity": "error",
        "matches": [
          {
            "file": "utils/dynamic.py",
            "range": { "start": { "line": 45, "column": 8 }, "end": { "line": 45, "column": 25 } },
            "code": "eval(user_input)"
          },
          {
            "file": "handlers/admin.py",
            "range": { "start": { "line": 112, "column": 12 }, "end": { "line": 112, "column": 30 } },
            "code": "exec(code_string)"
          }
        ]
      }
    },
    "logging": {
      "printf": {
        "count": 5,
        "message": "Use structured logging instead of fmt.Printf",
        "severity": "warning",
        "matches": [
          {
            "file": "handler.go",
            "range": { "start": { "line": 42, "column": 2 }, "end": { "line": 42, "column": 38 } },
            "code": "fmt.Printf(\"User: %s\", user)"
          }
        ]
      }
    }
  }
}

Configuration Options

AST-Grep Collector Inputs

Input	Required	Default	Description
`rules`	Required	—	Multi-line YAML string containing ast-grep rules. Use YAML multi-document syntax (---) to define multiple rules. Rule IDs should follow the format <category>.<subcategory> to map to Component JSON paths. Example: id: security.sql_concat -> .code_patterns.security.sql_concat
`exclude_paths`	Optional	`vendor,node_modules,.git,dist,build`	Comma-separated paths to exclude from scanning
`max_matches_per_rule`	Optional	`100`	Maximum matches to report per rule (prevents huge output)
`debug`	Optional	`false`	Enable debug output (echoes rules and raw ast-grep output)

Feature Flags Guardrails Inputs

Input	Required	Default	Description
`max_days`	Optional	`90`	Maximum number of days a feature flag should exist before failing the check

Learn More

Guardrail · Feature Flags Guardrails Feature Flags Age View all compatible integrations

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Collector AST-Grep Collector View full documentation

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