local_storage storeItem/getItem/removeItem validation errors bypass FES and don't prevent invalid operations

[MASTERsj01]

Increasing access

The Friendly Error System (FES) exists to provide beginner-friendly, translatable error messages. When parts of the codebase bypass FES with raw console.log(), those messages cannot be translated via i18n and are not suppressed by p5.disableFriendlyErrors = true. Additionally, when validation errors don't halt execution, invalid data gets silently stored, causing confusing behavior for beginners.

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build process
• Unit testing
• Internationalization
• Friendly errors
• Other (specify if possible)

Feature enhancement details

Five methods in src/data/local_storage.js use raw console.log() for validation errors instead of the Friendly Error System. Worse, some of these validations don't prevent the invalid operation from proceeding.

Affected locations in src/data/local_storage.js:

Function	Line	Message	Blocks execution?
storeItem()	L125	Non-string key warning	❌ No — stores anyway
storeItem()	L130	Key ending with p5TypeID warning	❌ No — stores anyway
storeItem()	L136	Undefined value warning	❌ No — stores anyway
getItem()	L283	Unable to determine stored type	❌ No — continues
removeItem()	L447	Non-string key warning	❌ No — removes anyway

Example of current code:

// storeItem() at line 123
p5.prototype.storeItem = function(key, value) {
  if (typeof key !== 'string') {
    console.log(
      `The argument that you passed to storeItem() - ${key} is not a string.`
    );
  }
  if (key.endsWith('p5TypeID')) {
    console.log(
      `The argument that you passed to storeItem() - ${key} must not end with 'p5TypeID'.`
    );
  }
  if (typeof value === 'undefined') {
    console.log('You cannot store undefined variables using storeItem().');
  }
  // ⚠️ Execution continues even after errors above — invalid data gets stored!
  let type = typeof value;
  // ...stores the value anyway...
};

Two problems here:

1. FES bypass: All 5 messages use raw console.log() instead of p5._friendlyError(), so they aren't suppressed by p5.disableFriendlyErrors = true and can't be translated via i18n.

2. Missing early returns: storeItem() logs the error but still proceeds to store the invalid key/value. For example, passing an undefined value logs a warning but still calls localStorage.setItem(key, undefined). Similarly, removeItem() warns about non-string keys but still tries to remove.

Expected behavior:

These validation messages should use p5._friendlyError() and the functions should return early after detecting invalid input, so that invalid data is not silently stored or removed.

Additional context:

This is consistent with ongoing efforts to migrate raw console.log/console.warn calls to FES across the codebase. The p5.TypedDict module in the same Data sub-area has similar patterns.

I'd be happy to work on this if it gets approved!

[MASTERsj01]

Consolidated into #8621