type/family-conformance

Status: active

Default severity: warning

What it checks

For every node in the snapshot, the rule reads the computed font-family value and splits it into a comma-separated list of family names. Outer quotes are stripped from each entry. A violation fires when none of the parsed families match any entry in type.families (case-insensitive comparison).

The rule MUST skip a node when:

• the node has no computed font-family value;
• the computed value is empty or whitespace-only;
• or type.families is empty (the rule is a no-op).

Why it matters

A type system defines which font families belong in a product. Using an off-brand family (a system default fallback, a debug font, a copy-pasted Google Fonts import that was never removed) undermines visual consistency. This rule catches those before they ship.

Example violation

{
  "rule_id": "type/family-conformance",
  "severity": "warning",
  "message": "`html > body > p` uses font-family `\"Comic Sans MS\", cursive` which is not in type.families.",
  "selector": "html > body > p",
  "viewport": "desktop",
  "dom_order": 3,
  "fix": {
    "kind": {
      "kind": "description",
      "text": "Use one of the allowed font families: Inter, sans-serif."
    },
    "description": "Replace `font-family` with one of the allowed families (Inter, sans-serif).",
    "confidence": "medium"
  },
  "doc_url": "https://plumb.aramhammoudeh.com/rules/type-family-conformance"
}

Configuration

type.families is the list of allowed font-family names. Default is empty (the rule is a no-op).

[type]
families = ["Inter", "sans-serif"]

Matching is case-insensitive. If any family in the element’s font-family stack matches any entry in type.families, the element passes.

Suppression

Disable the rule for an entire run:

[rules."type/family-conformance"]
enabled = false

Bump or lower the severity:

[rules."type/family-conformance"]
severity = "info"

See also

• type/scale-conformance — the sibling rule for font-size tokens.
• type/weight-conformance — the sibling rule for font-weight tokens.