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The consistency rule type ensures that variant spellings or terms aren’t mixed within the same document. When multiple valid options exist, this rule enforces picking one and sticking with it.

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How It Works

The consistency rule tracks pairs of alternatives defined in the either map. If both variants appear in the same file, it triggers an alert. This is file-scoped, meaning consistency is enforced across the entire document.

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Parameters

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either
map
required
A map of option1: option2 pairs. Only one option from each pair should appear in a document.
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ignorecase
boolean
default:"false"
Makes pattern matching case-insensitive when set to true.
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nonword
boolean
default:"false"
Removes the default word boundaries (\b) when set to true.

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Examples

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Spelling Consistency

Enforce consistent spelling across British and American English: 
extends: consistency
message: "Inconsistent spelling of '%s'."
level: error
ignorecase: true
either:
  advisor: adviser
  centre: center
  colour: color
  emphasise: emphasize
  finalise: finalize
  focussed: focused
  labour: labor
  organise: organize

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Smart Quotes vs Straight Quotes

Ensure consistent use of quote styles: 
extends: consistency
message: "Inconsistent use of '%s' ('smart' mixed with 'dumb')"
level: error
scope: text
nonword: true
either:
  '"': '[""]'
  "'": '[''']'

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Hyphenation Consistency

Enforce consistent hyphenation of compound terms: 
extends: consistency
message: "Inconsistent hyphenation of '%s'."
level: warning
ignorecase: true
either:
  built-in: builtin
  e-mail: email
  open-source: opensource

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Brand Name Variants

Ensure consistent brand name usage: 
extends: consistency
message: "Use '%s' consistently throughout the document."
level: error
ignorecase: false
either:
  GitHub: Github
  JavaScript: Javascript
  PostgreSQL: Postgres

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Date Format Consistency

Enforce consistent date formatting: 
extends: consistency
message: "Use consistent date format: '%s'."
level: warning
nonword: true
either:
  '\d{1,2}/\d{1,2}/\d{4}': '\d{4}-\d{2}-\d{2}'

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Use Cases

The consistency rule is ideal for:
  • Enforcing spelling consistency (US vs UK English)
  • Maintaining consistent hyphenation
  • Ensuring uniform quote style
  • Preventing mixed terminology
  • Standardizing date/time formats

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File-Level Scope

The consistency rule operates at the file level. It tracks all occurrences across the entire document and only triggers when both variants appear in the same file.Unlike other rules, it doesn’t matter which variant you choose—just that you use only one consistently throughout the document.

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Technical Details

Internally, the consistency rule (internal/check/consistency.go:80-112):
  1. Creates a separate check step for each key-value pair in either
  2. Compiles each pair into a regex with named capture groups
  3. Stores all matches in the file’s Sequences array
  4. If both names from a pair appear in Sequences, triggers an alert
  5. Uses core.AllStringsInSlice() to check for complete pairs
The rule creates named capture groups for tracking: 
chkRE = fmt.Sprintf("(?P<%s>%s)|(?P<%s>%s)", subs[0], v1, subs[1], v2)
This allows Vale to track which variant was used throughout the document.

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Multiple Pairs

You can define multiple pairs in a single rule. Vale will check each pair independently: 
extends: consistency
message: "Inconsistent spelling of '%s'."
level: error
either:
  color: colour
  center: centre
  organize: organise
Each pair is evaluated separately, so you could use “color” and “centre” in the same document without triggering alerts (though that would be unusual).

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Case Sensitivity

By default, consistency rules are case-sensitive. Set ignorecase: true to treat “Color” and “color” as the same variant: 
extends: consistency
message: "Inconsistent spelling of '%s'."
level: error
ignorecase: true
either:
  Color: Colour
  • substitution: Use when you want to enforce one specific variant (rather than just consistency)
  • existence: Use when you want to flag specific terms regardless of alternatives
  • spelling: Use for general spell-checking with dictionaries

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