python.lang.maintainability.useless-innerfunction.useless-inner-function

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function $FF is defined inside a function but never used

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Defintion

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rules:
  - id: useless-inner-function
    patterns:
      - pattern-not-inside: |
          def $F(...):
              ...
              def $FF(...):
                 ...
              ...
              <... $FF ...>
      - pattern-not-inside: |
          def $F(...):
              ...
              class $CLAZZ(...):
                ...
      - pattern-inside: |
          def $F(...):
            ...
            def $FF(...):
               ...
            ...
      - pattern: |
          def $FF(...):
            ...
      - pattern-not: |
          @$DECORATOR
          def $FF(...):
            ...
    message: function `$FF` is defined inside a function but never used
    languages:
      - python
    severity: ERROR
    metadata:
      category: maintainability
      technology:
        - python
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]

Examples

useless-innerfunction.py

def A():
    print_error('test')

    # ruleid:useless-inner-function
    def B():
        print_error('again')

    # ruleid:useless-inner-function
    def C():
        print_error('another')
    return None

def A():
    print_error('test')

    # ok:useless-inner-function
    def B():
        print_error('again')

    # ok:useless-inner-function
    def C():
        print_error('another')

    # ok:useless-inner-function
    @something
    def D():
        print_error('with decorator')

    return B(), C()

def foo():
    # ok:useless-inner-function
    def bar():
        print("hi mom")
    return bar

def create_decorating_metaclass(decorators, prefix='test_'):
    class DecoratingMethodsMetaclass(type):
        # ok:useless-inner-function
        def __new__(cls, name, bases, namespace):
            namespace_items = tuple(namespace.items())
            for key, val in namespace_items:
                if key.startswith(prefix) and callable(val):
                    for dec in decorators:
                        val = dec(val)
                    namespace[key] = val
            return type.__new__(cls, name, bases, dict(namespace))

    return DecoratingMethodsMetaclass

def dec(f):
    # ok:useless-inner-function
    def inner(*args, **kwargs):
        return f(*args, **kwargs)
    result = other_dec(inner)
    return result

def decorator_factory( foo ):
    def decorator( function ):
        # https://github.com/returntocorp/semgrep-rules/issues/660
        # ok:useless-inner-function
        def function_wrapper( *args, **kwargs ):
            # Do something with 'foo'.
            return function( *args, **kwargs )
        return function_wrapper
    return decorator

@decorator_factory( 'bar' )
def test( ): ''' Simple reproducer. '''