mcp-server-semgrep/semgrep-rules/python/lang/correctness/common-mistakes/is-comparison-string.yaml

MCP Server for Semgrep Integration - static code analysis with AI

rules:
  - id: identical-is-comparison
    pattern: $S is $S
    message: Found identical comparison using is. Ensure this is what you intended.
    languages: [python]
    severity: ERROR
    metadata:
      category: correctness
      technology:
        - python
  - id: string-is-comparison
    patterns:
      - pattern-not: $S is None
      - pattern-not: type($X) is $T
      - pattern-not: $S is True
      - pattern-not: $S is False
      - pattern-not: $S is ""
      - pattern-either:
          - pattern: $S is "..."
            # quotes needed b/c YAML complains if starting with "..."
          - pattern: '"..." is $S'
    message: >-
      Found string comparison using 'is' operator. The 'is' operator
      is for reference equality, not value equality, and therefore should
      not be used to compare strings. For more information, see
      https://github.com/satwikkansal/wtfpython#-how-not-to-use-is-operator"
    languages: [python]
    severity: ERROR
    metadata:
      category: correctness
      technology:
        - python