**/*.ts: - Use the Onion Pattern to organize a package's code in layers

• Try to use immutable code and avoid sharing state across different functions, objects, and systems
• Try to build code that's idempotent whenever possible
• Prefer functional programming style functions: small, deterministic, 1 input, 1 output
• Minimize coupling / dependencies
• Avoid modifying objects received as parameter
• Only add comments to code to explain why something was done, not how it works
• Naming
  • classes, enums: PascalCase
  • constants, variables, functions: camelCase
  • file names: kebab-case
  • table and column names: snake_case
  • Use meaningful names, so whoever is reading the code understands what it means
  • Don’t use negative names, like notEnabled, prefer isDisabled
  • For numeric values, if the type doesn’t convey the unit, add the unit to the name
• Typescript
  • Use types
  • Prefer const instead of let
  • Avoid any and casting from any to other types
  • Type predicates: only applicable to narrow down the type, not to force a complete type conversion
  • Prefer deconstructing parameters for functions instead of multiple parameters that might be of
    the same type
  • Don’t use null inside the app, only on code interacting with external interfaces/services,
    like DB and HTTP; convert to undefined before sending inwards into the code
  • Use async/await instead of .then()
  • Use the strict equality operator ===, don’t use abstract equality operator ==
  • When calling a Promise-returning function asynchronously (i.e., not awaiting), use .catch() to
    handle errors (see processAsyncError and emptyFunction depending on the case)
  • Date and Time
    • Always use buildDayjs() to create dayjs instances
    • Prefer dayjs.duration(...) to create duration consts and keep them as duration
• Prefer Nullish Coalesce (??) than the OR operator (||) to provide a default value
• Avoid creating arrow functions
• Use truthy syntax instead of in - i.e., if (data.link) not if ('link' in data)
• Error handling
  • Pass the original error as the new one’s cause so the stack trace is persisted
  • Error messages should have a static message - add dynamic data to MetriportError's additionalInfo prop
  • Avoid sending multiple events to Sentry for a single error
• Global constants and variables
  • Move literals to constants declared after imports when possible (avoid magic numbers)
  • Avoid shared, global objects
• Avoid using console.log and console.error in packages other than utils, infra and shared,
  and try to use out().log instead
• Avoid multi-line logs
  • don't send objects as a second parameter to console.log() or out().log()
  • don't create multi-line strings when using JSON.stringify()
• Use eslint to enforce code style
• Use prettier to format code
• max column length is 100 chars
• multi-line comments use /** */
• scripts: top-level comments go after the import

• packages/utils/src/fhir-converter/count-bundle-refs.ts
• packages/core/src/external/fhir/shared/__tests__/deep-search.test.ts
• packages/core/src/external/fhir/shared/bundle.ts

[error] 57-57: Use a regular expression literal instead of the RegExp constructor.

Regular expression literals avoid some escaping required in a string literal, and are easier to analyze statically.
Safe fix: Use a literal notation instead.

(lint/complexity/useRegexLiterals)