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: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: quotemark

Enforces quote character for string literals.

Notes

• Has Fix

Config

Five arguments may be optionally provided:

• "single" enforces single quotes.
• "double" enforces double quotes.
• "backtick" enforces backticks.
• "jsx-single" enforces single quotes for JSX attributes.
• "jsx-double" enforces double quotes for JSX attributes.
• "avoid-template" forbids single-line untagged template strings that do not contain string interpolations. Note that backticks may still be used if "avoid-escape" is enabled and both single and double quotes are present in the string (the latter option takes precedence).
• "avoid-escape" allows you to use the "other" quotemark in cases where escaping would normally be required. For example, [true, "double", "avoid-escape"] would not report a failure on the string literal 'Hello "World"'.

Examples

"quotemark": true,single,avoid-escape,avoid-template

"quotemark": true,single,jsx-double

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "single",
      "double",
      "backtick",
      "jsx-single",
      "jsx-double",
      "avoid-escape",
      "avoid-template"
    ]
  },
  "minLength": 0,
  "maxLength": 5
}

For more information see this page.

Rule: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: quotemark

Enforces quote character for string literals.

Notes

• Has Fix

Config

Five arguments may be optionally provided:

• "single" enforces single quotes.
• "double" enforces double quotes.
• "backtick" enforces backticks.
• "jsx-single" enforces single quotes for JSX attributes.
• "jsx-double" enforces double quotes for JSX attributes.
• "avoid-template" forbids single-line untagged template strings that do not contain string interpolations. Note that backticks may still be used if "avoid-escape" is enabled and both single and double quotes are present in the string (the latter option takes precedence).
• "avoid-escape" allows you to use the "other" quotemark in cases where escaping would normally be required. For example, [true, "double", "avoid-escape"] would not report a failure on the string literal 'Hello "World"'.

Examples

"quotemark": true,single,avoid-escape,avoid-template

"quotemark": true,single,jsx-double

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "single",
      "double",
      "backtick",
      "jsx-single",
      "jsx-double",
      "avoid-escape",
      "avoid-template"
    ]
  },
  "minLength": 0,
  "maxLength": 5
}

For more information see this page.

Rule: radix

Requires the radix parameter to be specified when calling parseInt.

Rationale

From MDN:

Always specify this parameter to eliminate reader confusion and to guarantee predictable behavior. Different implementations produce different results when a radix is not specified, usually defaulting the value to 10.

Config

Not configurable.

Examples

"radix": true

For more information see this page.

Rule: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: quotemark

Enforces quote character for string literals.

Notes

• Has Fix

Config

Five arguments may be optionally provided:

• "single" enforces single quotes.
• "double" enforces double quotes.
• "backtick" enforces backticks.
• "jsx-single" enforces single quotes for JSX attributes.
• "jsx-double" enforces double quotes for JSX attributes.
• "avoid-template" forbids single-line untagged template strings that do not contain string interpolations. Note that backticks may still be used if "avoid-escape" is enabled and both single and double quotes are present in the string (the latter option takes precedence).
• "avoid-escape" allows you to use the "other" quotemark in cases where escaping would normally be required. For example, [true, "double", "avoid-escape"] would not report a failure on the string literal 'Hello "World"'.

Examples

"quotemark": true,single,avoid-escape,avoid-template

"quotemark": true,single,jsx-double

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "single",
      "double",
      "backtick",
      "jsx-single",
      "jsx-double",
      "avoid-escape",
      "avoid-template"
    ]
  },
  "minLength": 0,
  "maxLength": 5
}

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-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.

Rule: no-inferrable-types

Disallows explicit type declarations for variables or parameters initialized to a number, string, or boolean.

Rationale

Explicit types where they can be easily inferred by the compiler make code more verbose.

Notes

• TypeScript Only
• Has Fix

Config

Two arguments may be optionally provided:

• ignore-params allows specifying an inferrable type annotation for function params. This can be useful when combining with the typedef rule.
• ignore-properties allows specifying an inferrable type annotation for class properties.

Examples

"no-inferrable-types": true

"no-inferrable-types": true,ignore-params

"no-inferrable-types": true,ignore-params,ignore-properties

Schema

{
  "type": "array",
  "items": {
    "type": "string",
    "enum": [
      "ignore-params",
      "ignore-properties"
    ]
  },
  "minLength": 0,
  "maxLength": 2
}

For more information see this page.