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FSH Lint

Cardinality Rules

Overview

Section titled “Overview”

Cardinality rules validate that element cardinality constraints are valid and consistent.

Rules

Section titled “Rules”

correctness/invalid-cardinality

Section titled “correctness/invalid-cardinality”

Severity: Error Fixable: Yes (safe)

Cardinality must be specified as min..max where min <= max.

Example:

// ✓ Good
Profile: PatientProfile
* name 1..1
* telecom 0..*


// ✗ Bad
Profile: PatientProfile
* name 2..1  // min > max

correctness/cardinality-conflict

Section titled “correctness/cardinality-conflict”

Severity: Error Fixable: No

Multiple cardinality rules on the same element must be compatible.

Example:

// ✗ Bad - Conflicting cardinality
Profile: PatientProfile
* name 1..1
* name 0..*  // Conflicts with previous rule

suspicious/redundant-cardinality

Section titled “suspicious/redundant-cardinality”

Severity: Info Fixable: Yes (safe)

Cardinality that matches the parent is redundant.

Example:

// ⚠ Redundant
Profile: PatientProfile
Parent: Patient
* identifier 0..*  // Same as base Patient.identifier

Rationale

Section titled “Rationale”

Valid cardinality ensures:

  • FHIR validation works correctly
  • Clear data requirements
  • Prevents impossible constraints