Simplify Your Rules Using Symbolic Propagation Techniques

Original Post: Keep your rules simple with symbolic propagation

tl;dr: Symbolic propagation is a new experimental feature in Semgrep that generalizes constant propagation, enabling pattern matching even with intermediate variable assignments. For example, return 42 will match return C where C = 42. Similarly, the pattern $OBJ.foo().bar() can now match code with intermediate assignments like:

def test(obj):
    x = obj.foo()
    x.bar()

This eliminates the need for complex patterns that account for various code shapes involving intermediate assignments. To use this feature, set symbolic_propagation: true in the rule options. This feature simplifies writing powerful and succinct Semgrep rules, and although still experimental, it aims to become a default capability soon.

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