replace unbounded retry loops with bounded exponential backoff in Turtle and Block cache methods

[Ashutoshx7]

Summary

This PR fixes critical unbounded retry loops in Turtle._createCache() and Turtle.updateCache() that can cause infinite loops and browser hangs when canvas container bounds are never available. It also consolidates duplicated retry logic across turtle.js and block.js into a shared, well-tested utility.

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Problems Fixed

1. Unbounded retry in Turtle._createCache() (infinite loop)

The original code called setTimeout(() => this._createCache(), 200) with no maximum retry limit. If container.getBounds() never returns a value (e.g., due to a rendering failure or detached container), this loops forever, consuming memory and CPU.

2. Broken promise chain in Turtle.updateCache() (silent failures + infinite recursion)

• The recursive this.updateCache() call was neither awaited nor returned, so failures were silently swallowed
• No retry limit — infinite recursion if bounds stays null
• Logged "Block container" instead of "Turtle container" (copy-paste bug)

3. Code duplication across turtle.js and block.js

Three separate hand-rolled retry implementations existed with inconsistent patterns. block.js already had bounded retries with exponential backoff, but turtle.js did not.

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Changes

File	What changed
js/utils/retryWithBackoff.js	New — Shared retry utility with configurable max retries, exponential backoff, and proper Promise semantics
js/turtle.js	_createCache(): unbounded setTimeout → bounded retryWithBackoff() (max 20 retries). updateCache(): unbounded async recursion → bounded retry (max 15), fixed log message
js/block.js	_createCache() and updateCache(): replaced 60+ lines of hand-rolled retry logic with ~30 lines using shared utility. Restored missing blockBlocks global declaration
js/loader.js	Added RequireJS shim entry for utils/retryWithBackoff with dependency declarations for activity/turtle and activity/block
js/activity.js	Added "utils/retryWithBackoff" to MYDEFINES array so the module loads at startup
js/tests/retryWithBackoff.test.js	New — 19 unit tests covering: immediate success, retry behavior, exponential delay verification, max retries exceeded, error propagation, edge cases

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Before / After

Turtle._createCache() — Before

_createCache() {
    this.bounds = this.container.getBounds();
    if (this.bounds == null) {
        setTimeout(() => {
            this._createCache();
        }, 200); // ← No limit. Runs forever.
    } else {
        this.container.cache(this.bounds.x, this.bounds.y, this.bounds.width, this.bounds.height);
    }
}

Turtle._createCache() — After

_createCache() {
    return retryWithBackoff({
        check: () => {
            this.bounds = this.container.getBounds();
            return this.bounds;
        },
        onSuccess: (bounds) => {
            this.container.cache(bounds.x, bounds.y, bounds.width, bounds.height);
        },
        maxRetries: 20,
        initialDelay: 50,
        errorMessage: "Turtle._createCache: could not get container bounds after 20 attempts"
    });
}

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.

[shashank03-dev]

In retryWithBackoff.js, since you’re already using await, you could simplify the logic by replacing the new Promise wrapper and recursion with a standard await for-loop. It would shorten the code and it would look a bit modern too.

[github-actions]

✅ All Jest tests passed! This PR is ready to merge.