Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 44.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 44.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Continuation lines indentation.

Continuation lines should align wrapped elements either vertically
using Python's implicit line joining inside parentheses, brackets
and braces, or using a hanging indent.

When using a hanging indent these considerations should be applied:
- there should be no arguments on the first line, and
- further indentation should be used to clearly distinguish itself
  as a continuation line.

Okay: a = (\n)
E123: a = (\n    )

Okay: a = (\n    42)
E121: a = (\n   42)
E122: a = (\n42)
E123: a = (\n    42\n    )
E124: a = (24,\n     42\n)
E125: if (\n    b):\n    pass
E126: a = (\n        42)
E127: a = (24,\n      42)
E128: a = (24,\n    42)
E129: if (a or\n    b):\n    pass
E131: a = (\n    42\n 24)

Avoid breaks after binary operators.

The preferred place to break around a binary operator is before the
operator, not after it.

W504: (width == 0 +\n height == 0)
W504: (width == 0 and\n height == 0)
W504: var = (1 &\n       ~2)

Okay: foo(\n    -x)
Okay: foo(x\n    [])
Okay: x = '''\n''' + ''
Okay: x = '' + '''\n'''
Okay: foo(x,\n    -y)
Okay: foo(x,  # comment\n    -y)

The following should be W504 but unary_context is tricky with these
Okay: var = (1 /\n       -2)
Okay: var = (1 +\n       -1 +\n       -2)

Avoid breaks after binary operators.

The preferred place to break around a binary operator is before the
operator, not after it.

W504: (width == 0 +\n height == 0)
W504: (width == 0 and\n height == 0)
W504: var = (1 &\n       ~2)

Okay: foo(\n    -x)
Okay: foo(x\n    [])
Okay: x = '''\n''' + ''
Okay: x = '' + '''\n'''
Okay: foo(x,\n    -y)
Okay: foo(x,  # comment\n    -y)

The following should be W504 but unary_context is tricky with these
Okay: var = (1 /\n       -2)
Okay: var = (1 +\n       -1 +\n       -2)

Avoid breaks after binary operators.

The preferred place to break around a binary operator is before the
operator, not after it.

W504: (width == 0 +\n height == 0)
W504: (width == 0 and\n height == 0)
W504: var = (1 &\n       ~2)

Okay: foo(\n    -x)
Okay: foo(x\n    [])
Okay: x = '''\n''' + ''
Okay: x = '' + '''\n'''
Okay: foo(x,\n    -y)
Okay: foo(x,  # comment\n    -y)

The following should be W504 but unary_context is tricky with these
Okay: var = (1 /\n       -2)
Okay: var = (1 +\n       -1 +\n       -2)