ast-analyzer

What this skill does

## AST Analyzer Skill

Provides comprehensive Abstract Syntax Tree (AST) analysis capabilities for understanding code at a structural level, identifying patterns, dependencies, and potential issues that simple text analysis would miss.

## Core Philosophy

**Beyond Text Analysis**: While traditional code analysis works with text patterns, AST analysis understands the actual structure and semantics of code, enabling:
- Precise refactoring without breaking logic
- Accurate dependency tracking
- Reliable impact analysis
- Language-aware pattern detection

## Core Capabilities

### 1. AST Parsing

**Multi-Language Support**:
```python
# Python example using ast module
import ast

def parse_python_code(source_code):
    tree = ast.parse(source_code)

    # Extract all function definitions
    functions = [
        node for node in ast.walk(tree)
        if isinstance(node, ast.FunctionDef)
    ]

    # Extract all class definitions
    classes = [
        node for node in ast.walk(tree)
        if isinstance(node, ast.ClassDef)
    ]

    return {
        "functions": len(functions),
        "classes": len(classes),
        "function_details": [
            {
                "name": f.name,
                "args": [arg.arg for arg in f.args.args],
                "line": f.lineno,
                "decorators": [d.id for d in f.decorator_list if isinstance(d, ast.Name)]
            }
            for f in functions
        ]
    }
```

**JavaScript/TypeScript Support**:
```javascript
// Using babel or acorn parser
const parser = require('@babel/parser');
const traverse = require('@babel/traverse').default;

function parseJavaScriptCode(sourceCode) {
    const ast = parser.parse(sourceCode, {
        sourceType: 'module',
        plugins: ['jsx', 'typescript']
    });

    const analysis = {
        functions: [],
        classes: [],
        imports: [],
        exports: []
    };

    traverse(ast, {
        FunctionDeclaration(path) {
            analysis.functions.push({
                name: path.node.id.name,
                params: path.node.params.map(p => p.name),
                async: path.node.async
            });
        },
        ClassDeclaration(path) {
            analysis.classes.push({
                name: path.node.id.name,
                methods: path.node.body.body.filter(
                    m => m.type === 'ClassMethod'
                )
            });
        }
    });

    return analysis;
}
```

### 2. Function and Class Hierarchy Analysis

**Hierarchy Extraction**:
```python
def analyze_class_hierarchy(ast_tree):
    """Extract complete class inheritance hierarchy."""
    hierarchy = {}

    for node in ast.walk(ast_tree):
        if isinstance(node, ast.ClassDef):
            class_info = {
                "name": node.name,
                "bases": [
                    base.id if isinstance(base, ast.Name) else str(base)
                    for base in node.bases
                ],
                "methods": [
                    m.name for m in node.body
                    if isinstance(m, ast.FunctionDef)
                ],
                "decorators": [
                    d.id for d in node.decorator_list
                    if isinstance(d, ast.Name)
                ],
                "line": node.lineno
            }
            hierarchy[node.name] = class_info

    # Build inheritance tree
    for class_name, info in hierarchy.items():
        info["children"] = [
            name for name, data in hierarchy.items()
            if class_name in data["bases"]
        ]

    return hierarchy
```

**Method Call Graph**:
```python
def build_call_graph(ast_tree):
    """Build function call graph showing dependencies."""
    call_graph = {}

    for node in ast.walk(ast_tree):
        if isinstance(node, ast.FunctionDef):
            function_name = node.name
            calls = []

            # Find all function calls within this function
            for child in ast.walk(node):
                if isinstance(child, ast.Call):
                    if isinstance(child.func, ast.Name):
                        calls.append(child.func.id)
                    elif isinstance(child.func, ast.Attribute):
                        calls.append(f"{child.func.value.id}.{child.func.attr}")

            call_graph[function_name] = {
                "calls": list(set(calls)),
                "complexity": calculate_complexity(node)
            }

    return call_graph
```

### 3. Variable Scope and Lifetime Tracking

**Scope Analysis**:
```python
def analyze_variable_scope(ast_tree):
    """Track variable definitions, assignments, and usage scope."""
    scopes = []

    class ScopeAnalyzer(ast.NodeVisitor):
        def __init__(self):
            self.current_scope = None
            self.scopes = {}

        def visit_FunctionDef(self, node):
            # Enter new scope
            scope_name = f"{self.current_scope}.{node.name}" if self.current_scope else node.name
            self.scopes[scope_name] = {
                "type": "function",
                "variables": {},
                "params": [arg.arg for arg in node.args.args],
                "line": node.lineno
            }

            old_scope = self.current_scope
            self.current_scope = scope_name

            # Analyze variable assignments in this scope
            for child in ast.walk(node):
                if isinstance(child, ast.Assign):
                    for target in child.targets:
                        if isinstance(target, ast.Name):
                            self.scopes[scope_name]["variables"][target.id] = {
                                "first_assignment": child.lineno,
                                "type": "local"
                            }

            self.current_scope = old_scope

        def visit_ClassDef(self, node):
            # Similar scope tracking for classes
            scope_name = f"{self.current_scope}.{node.name}" if self.current_scope else node.name
            self.scopes[scope_name] = {
                "type": "class",
                "variables": {},
                "methods": [m.name for m in node.body if isinstance(m, ast.FunctionDef)],
                "line": node.lineno
            }

    analyzer = ScopeAnalyzer()
    analyzer.visit(ast_tree)
    return analyzer.scopes
```

### 4. Code Pattern and Anti-Pattern Detection

**Common Patterns**:
```python
def detect_patterns(ast_tree):
    """Detect common code patterns and anti-patterns."""
    patterns_found = {
        "design_patterns": [],
        "anti_patterns": [],
        "code_smells": []
    }

    # Singleton pattern detection
    for node in ast.walk(ast_tree):
        if isinstance(node, ast.ClassDef):
            # Check for singleton indicators
            has_instance_attr = any(
                isinstance(n, ast.Assign) and
                any(isinstance(t, ast.Name) and t.id == '_instance' for t in n.targets)
                for n in node.body
            )

            has_new_method = any(
                isinstance(n, ast.FunctionDef) and n.name == '__new__'
                for n in node.body
            )

            if has_instance_attr and has_new_method:
                patterns_found["design_patterns"].append({
                    "pattern": "Singleton",
                    "class": node.name,
                    "line": node.lineno
                })

    # Anti-pattern: God class (too many methods)
    for node in ast.walk(ast_tree):
        if isinstance(node, ast.ClassDef):
            method_count = sum(1 for n in node.body if isinstance(n, ast.FunctionDef))

            if method_count > 20:
                patterns_found["anti_patterns"].append({
                    "pattern": "God Class",
                    "class": node.name,
                    "method_count": method_count,
                    "line": node.lineno,
                    "severity": "high"
                })

    # Code smell: Long function
    for node i