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 50.

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

Rule: whitespace

Enforces whitespace style conventions.

Rationale

Helps maintain a readable, consistent style in your codebase.

Notes

• Has Fix

Config

Several arguments may be optionally provided:

• "check-branch" checks branching statements (if/else/for/while) are followed by whitespace.
• "check-decl"checks that variable declarations have whitespace around the equals token.
• "check-operator" checks for whitespace around operator tokens.
• "check-module" checks for whitespace in import & export statements.
• "check-separator" checks for whitespace after separator tokens (,/;).
• "check-rest-spread" checks that there is no whitespace after rest/spread operator (...).
• "check-type" checks for whitespace before a variable type specification.
• "check-typecast" checks for whitespace between a typecast and its target.
• "check-type-operator" checks for whitespace between type operators | and &.
• "check-preblock" checks for whitespace before the opening brace of a block.
• "check-postbrace" checks for whitespace after an opening brace.

Examples

"whitespace": true,check-branch,check-operator,check-typecast

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "check-branch",
      "check-decl",
      "check-operator",
      "check-module",
      "check-separator",
      "check-rest-spread",
      "check-type",
      "check-typecast",
      "check-type-operator",
      "check-preblock",
      "check-postbrace"
    ]
  },
  "minLength": 0,
  "maxLength": 11
}

For more information see this page.

Rule: prefer-const

Requires that variable declarations use const instead of let and var if possible.

If a variable is only assigned to once when it is declared, it should be declared using 'const'

Notes

• Has Fix

Config

An optional object containing the property "destructuring" with two possible values:

• "any" (default) - If any variable in destructuring can be const, this rule warns for those variables.
• "all" - Only warns if all variables in destructuring can be const.

Examples

"prefer-const": true

"prefer-const": true,[object Object]

Schema

{
  "type": "object",
  "properties": {
    "destructuring": {
      "type": "string",
      "enum": [
        "all",
        "any"
      ]
    }
  }
}

For more information see this page.

Rule: curly

Enforces braces for if/for/do/while statements.

Rationale

if (foo === bar)
    foo++;
    bar++;

In the code above, the author almost certainly meant for both foo++ and bar++ to be executed only if foo === bar. However, they forgot braces and bar++ will be executed no matter what. This rule could prevent such a mistake.

Notes

• Has Fix

Config

One of the following options may be provided:

• "as-needed" forbids any unnecessary curly braces.
• "ignore-same-line" skips checking braces for control-flow statements that are on one line and start on the same line as their control-flow keyword

Examples

"curly": true

"curly": true,ignore-same-line

"curly": true,as-needed

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "as-needed",
      "ignore-same-line"
    ]
  }
}

For more information see this page.

Rule: no-trailing-whitespace

Disallows trailing whitespace at the end of a line.

Rationale

Keeps version control diffs clean as it prevents accidental whitespace from being committed.

Notes

• Has Fix

Config

Possible settings are:

• "ignore-template-strings": Allows trailing whitespace in template strings.
• "ignore-comments": Allows trailing whitespace in comments.
• "ignore-jsdoc": Allows trailing whitespace only in JSDoc comments.
• "ignore-blank-lines": Allows trailing whitespace on empty lines.

Examples

"no-trailing-whitespace": true

"no-trailing-whitespace": true,ignore-comments

"no-trailing-whitespace": true,ignore-jsdoc

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-comments",
      "ignore-jsdoc",
      "ignore-template-strings",
      "ignore-blank-lines"
    ]
  }
}

For more information see this page.

Rule: curly

Enforces braces for if/for/do/while statements.

Rationale

if (foo === bar)
    foo++;
    bar++;

In the code above, the author almost certainly meant for both foo++ and bar++ to be executed only if foo === bar. However, they forgot braces and bar++ will be executed no matter what. This rule could prevent such a mistake.

Notes

• Has Fix

Config

One of the following options may be provided:

• "as-needed" forbids any unnecessary curly braces.
• "ignore-same-line" skips checking braces for control-flow statements that are on one line and start on the same line as their control-flow keyword

Examples

"curly": true

"curly": true,ignore-same-line

"curly": true,as-needed

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "as-needed",
      "ignore-same-line"
    ]
  }
}

For more information see this page.

Rule: curly

Enforces braces for if/for/do/while statements.

Rationale

if (foo === bar)
    foo++;
    bar++;

In the code above, the author almost certainly meant for both foo++ and bar++ to be executed only if foo === bar. However, they forgot braces and bar++ will be executed no matter what. This rule could prevent such a mistake.

Notes

• Has Fix

Config

One of the following options may be provided:

• "as-needed" forbids any unnecessary curly braces.
• "ignore-same-line" skips checking braces for control-flow statements that are on one line and start on the same line as their control-flow keyword

Examples

"curly": true

"curly": true,ignore-same-line

"curly": true,as-needed

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "as-needed",
      "ignore-same-line"
    ]
  }
}

For more information see this page.