from typing import Any, Dict, List, Optional
def scan_m_practices(query_executor: Any, dmv_cap: int = 1000, issues_max: Optional[int] = None) -> Dict[str, Any]:
"""Scan M expressions for common issues.
Returns a dict with keys: success: bool, count: int, issues: List[dict]
"""
try:
m_query = f'''EVALUATE
SELECTCOLUMNS(
TOPN({dmv_cap}, $SYSTEM.TMSCHEMA_EXPRESSIONS),
"Name", [Name],
"Expression", [Expression],
"Kind", [Kind]
)'''
data = query_executor.validate_and_execute_dax(m_query, dmv_cap)
if not isinstance(data, dict) or not data.get('success'):
# Fallback to TOM enumeration on Desktop where DMV may be blocked
try:
data = query_executor.enumerate_m_expressions_tom(dmv_cap)
except Exception as _e:
return data if isinstance(data, dict) else {'success': False, 'error': str(_e)}
issues: List[Dict[str, Any]] = []
for row in data.get('rows', []):
if str(row.get('Kind', '')).upper() != 'M':
continue
name = row.get('Name') or '<unknown>'
expr = (row.get('Expression') or '')
expr_lower = expr.lower()
if 'table.buffer(' in expr_lower:
issues.append({'rule': 'M001', 'severity': 'warning', 'name': name, 'description': 'Table.Buffer used; can cause high memory usage if misapplied.'})
if 'web.contents(' in expr_lower and ('relativepath' not in expr_lower and 'query=' not in expr_lower):
issues.append({'rule': 'M002', 'severity': 'info', 'name': name, 'description': 'Web.Contents without RelativePath/Query options may be less cache-friendly.'})
# Detect absolute Windows (C:\) or URL-like (C:/) paths
if 'excel.workbook(file.contents(' in expr_lower and (':\\' in expr_lower or ':/' in expr_lower):
issues.append({'rule': 'M003', 'severity': 'warning', 'name': name, 'description': 'Excel.Workbook(File.Contents) with absolute path detected; consider parameterizing path.'})
if 'table.selectrows(' in expr_lower:
issues.append({'rule': 'M004', 'severity': 'info', 'name': name, 'description': 'Table.SelectRows found; ensure filtering is pushed to source where possible.'})
if isinstance(issues_max, int) and issues_max > 0 and len(issues) > issues_max:
issues = issues[:issues_max]
return {'success': True, 'count': len(issues), 'issues': issues}
except Exception as e:
return {'success': False, 'error': str(e)}
