Never Nesting

Each level of indentation is one more condition the reader must hold as true to understand the innermost line. SonarSource's cognitive-complexity metric formalizes this: every control structure costs +1, plus +1 for each level of nesting it sits under. Four sequential guard clauses cost 4; the same logic as four nested ifs costs 1+2+3+4 = 10. Nesting doesn't add difficulty linearly — it compounds. The Linux kernel style guide puts it bluntly: "if you need more than 3 levels of indentation, you're screwed anyway, and should fix your program."

Treat three levels as a soft ceiling and a fourth as a refactoring signal, not a formatting problem. The moves below flatten code; the last section covers the cases where flattening makes code worse.

Use this skill when