E11021: cognitive complexity exceeds limit - extract functions

What went wrong

Cognitive complexity measures how difficult code is to understand. Your function/method exceeds the maximum of 35.

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 765 (What is the cognitive complexity limit in EK9?)

[EK9-SPECIFIC FACTORS]

• Each control structure (if, while, for, switch, try) adds cost
• Nesting MULTIPLIES cost: depth 3 costs 3x more than depth 1
• Declaration guards (<-) add +1 penalty per guard
• Formula: (base_cost + guard_penalty) x nesting_depth

How to fix it

1. Extract nested logic into helper functions
2. Reduce nesting depth (target: 3-4 levels max)
3. Use stream pipelines for data transformations
4. Break up complex guard chains

See also

• E11021: cognitive complexity (this error)
• E11011: nesting depth limit
• E11010: cyclomatic complexity

https://ek9.io/quality.html#complexity https://ek9.io/forAI.json#$.qualityMetrics.metrics[?(@.errorCode=="E11021")]

Examples

Every example is compiled by the EK9 compiler: the first fails exactly as captioned, the others fix it.

Fails with E11021: cognitive complexity exceeds limit - extract functions

#!ek9
defines module error.e11021.bad

  defines function

    getA()
      <- rtn as String: "a"

    getB()
      <- rtn as String: "b"

    getC()
      <- rtn as String: "c"

    getD()
      <- rtn as String: "d"

    getE()
      <- rtn as String: "e"

    getF()
      <- rtn as String: "f"

    deepGuardChain()
      <- result as String: ""

      if a <- getA()
        if b <- getB()
          if c <- getC()
            if d <- getD()
              if e <- getE()
                if f <- getF()
                  result: `${a}${b}${c}${d}${e}${f}`

Fixed: Gather the values first, then make one decision

#!ek9
defines module error.e11021.good

  defines function

    getA()
      <- rtn as String: "a"

    getB()
      <- rtn as String: "b"

    getC()
      <- rtn as String: "c"

    combined()
      <- result as String: ""
      a <- getA()
      b <- getB()
      c <- getC()
      if a? and b? and c?
        result: `${a}${b}${c}`

Questions and answers

These Q&A entries show E11021 and its fix:

• Q765: What is the cognitive complexity limit in EK9?