mcp-server-semgrep/semgrep-rules/python/lang/best-practice/manual-collections-create.yaml

MCP Server for Semgrep Integration - static code analysis with AI

rules:
  - id: manual-defaultdict-dict-create
    message: manually creating a defaultdict - use collections.defaultdict(dict)
    languages: [python]
    severity: WARNING
    pattern-either:
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              if $KEY not in $DICT:
                  ...
                  $DICT[$KEY] = {}
                  ...
              $DICT[$KEY].update(...)
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              $DICT.setdefault($KEY, {}).update(...)
    metadata:
      category: best-practice
      technology:
        - python
  - id: manual-defaultdict-set-create
    message: manually creating a defaultdict - use collections.defaultdict(set)
    languages: [python]
    severity: WARNING
    pattern-either:
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              if $KEY not in $DICT:
                  ...
                  $DICT[$KEY] = set()
                  ...
              $DICT[$KEY].add(...)
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              $DICT.setdefault($KEY, set()).add(...)
    metadata:
      category: best-practice
      technology:
        - python
  - id: manual-defaultdict-list-create
    message: manually creating a defaultdict - use collections.defaultdict(list)
    languages: [python]
    severity: WARNING
    pattern-either:
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              if $KEY not in $DICT:
                  ...
                  $DICT[$KEY] = []
                  ...
              $DICT[$KEY].append(...)
      - pattern: |
          $DICT = {}
          ...
          for $KEY, $VALUE in $OTHERDICT.items():
              ...
              $DICT.setdefault($KEY, []).append(...)
    metadata:
      category: best-practice
      technology:
        - python
  - id: manual-counter-create
    pattern: |
      $DICT = {}
      ...
      for $KEY, $VALUE in $OTHERDICT.items():
          ...
          if $KEY not in $DICT:
              ...
              $DICT[$KEY] = 0
              ...
          $DICT[$KEY] += 1
    message: manually creating a counter - use collections.Counter
    languages: [python]
    severity: WARNING
    metadata:
      category: best-practice
      technology:
        - python