resolvePitchParams() error message hardcodes algorithm list - becomes stale when new variable-ratio algorithms added

[Elshayib]

Bug Report

Issue

In host.js, the resolvePitchParams() function has a hardcoded error message listing specific algorithms that support variable ratios. This error message becomes outdated when new algorithms are added that support variable ratios.

Location

host.js lines 25-30

Details

export function resolvePitchParams(opts) {
  let semitones = opts?.semitones ?? 0
  if (!Number.isFinite(semitones)) throw new TypeError('pitchShift: `semitones` must be a finite number')
  let raw = opts?.ratio
  if (typeof raw === 'function' || raw instanceof Float32Array) {
    throw new TypeError('pitchShift: variable `ratio` (function or Float32Array) is supported by vocoder, phaseLock, transient, formant, paulstretch, sms, hpss, and sample')
  }
  // ...
}

The Bug: The error message explicitly lists algorithms: "vocoder, phaseLock, transient, formant, paulstretch, sms, hpss, and sample". When a new algorithm is added that supports variable ratios (e.g., a future melody algorithm), the error message won't be updated, misleading users.

Additionally, lpc and delay algorithms were added later (as seen in pitch-shift.js and test.js) and also support variable ratios, but they're not in this error message list.

Impact

• Medium: Misleading error messages when using variable ratios with newer algorithms
• Maintenance burden: every new variable-ratio algorithm requires updating this error message

Suggested Fix

Replace the hardcoded list with a reference to a central capability registry, or at minimum make the message generic:

if (typeof raw === 'function' || raw instanceof Float32Array) {
  throw new TypeError('pitchShift: variable `ratio` (function or Float32Array) is not supported by this algorithm. Use the main `pitchShift()` entry point which auto-selects a compatible method, or use one of the algorithms that explicitly supports variable ratios.')
}

Or better, maintain a SUPPORTS_VARIABLE_RATIO Set/Map that algorithms register themselves into:

// At top of host.js or in a shared capabilities file
const VARIABLE_RATIO_ALGORITHMS = new Set([
  'vocoder', 'phaseLock', 'transient', 'formant', 
  'paulstretch', 'sms', 'hpss', 'sample', 'delay', 'lpc'
])

export function resolvePitchParams(opts) {
  // ...
  if (typeof raw === 'function' || raw instanceof Float32Array) {
    const algos = [...VARIABLE_RATIO_ALGORITHMS].join(', ')
    throw new TypeError(`pitchShift: variable \`ratio\` (function or Float32Array) is supported by: ${algos}. Use the main \`pitchShift()\` entry point for auto-selection.`)
  }
  // ...
}

Then each algorithm file can import and register itself:

// In delay.js, lpc.js, etc.
import { VARIABLE_RATIO_ALGORITHMS } from './host.js'
VARIABLE_RATIO_ALGORITHMS.add('delay')

This makes the capability explicit and self-documenting.

Related Note

The lpc and delay algorithms (added in recent commits) support variable ratios per the tests but are missing from the error message list.