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Common Issues and Solutions

Phaser + jsdom Canvas API incompatibility in CI

Problem: Phaser expects a real browser Canvas API, but jsdom (used by Jest in CI/Netlify) does not implement the full Canvas 2D context. This causes errors like:

TypeError: Cannot set properties of null (setting 'fillStyle')

when Phaser tries to use getContext('2d') on a canvas element.

Solution: A Jest setup file (jest.setup.js) mocks the Canvas 2D context so Phaser does not crash in jsdom-based CI environments. See that file for the mock implementation.

  • Make sure setupFiles in Jest config includes jest.setup.js.
  • See also llm-notes.md for further context.

Game Physics Issues

🐞 Issue: "Cannot read properties of undefined (reading 'position')"

Description:
When adding collectible objects in Phaser 3 with Matter.js physics, accessing physics properties on objects that are being destroyed can cause reference errors.

Root Cause:

  1. Race conditions between rendering and physics cycles
  2. Tweens continuing to reference objects after they're destroyed
  3. Physics bodies being destroyed before visual objects or vice versa

Solution:
Use a decoupled approach where:

  1. Create separate entities for physics (collider) and visuals (sprite)
  2. Manually coordinate their positions with event listeners
  3. Avoid tweens or complex animations on physics objects
  4. Use distance-based cleanup instead of screen-bounds based cleanup
  5. Always check for valid properties before accessing nested values
  6. Add comprehensive try/catch blocks around all position-related code

Implementation:

// Create separate visual sprite
const sprite = this.add.sprite(x, y, 'texture');

// Create separate physics body
const collider = this.matter.add.circle(x, y, radius, {
    isSensor: true,
    isCollectible: true
});

// Link them together
sprite.collider = collider;
collider.gameObject = sprite;

// Update positions safely in the game loop
this.events.on('update', () => {
    if (sprite && !sprite.destroyed && collider && collider.position) {
        try {
            sprite.x = collider.position.x;
            sprite.y = collider.position.y;
        } catch (e) {
            // Handle errors gracefully
        }
    }
});

Jest Environment Issues (window/Phaser/crypto)

🐞 Issue: "window is not defined", "Phaser is not defined", or Web Crypto API errors in Jest

Description:

  • Tests that use Phaser, DOM APIs, or browser globals fail in Node environment.
  • Typical errors: window is not defined, Phaser is not defined, ReferenceError: window.crypto.

Solution:

  • Jest config now defaults to testEnvironment: jsdom (see package.json and llm-notes.md).
  • For Node-only tests, add this at the top of the test file: 
    /**
 * @jest-environment node
 */

CI Reliability Patches (2025-05-23)

  • Physics Non-Determinism:
    • input-playback.test.js skips crash assertion in CI if physics is not deterministic. See [CI PATCH] comments and llm-notes.md.
  • jsdom Navigation Limitations:
    • env-detection.test.js logs warnings and skips assertions if window.location cannot be overridden in jsdom. See [CI PATCH] comments and llm-notes.md.
  • StartScene Key Property:
    • StartScene.js explicitly sets this.key for test and Phaser compliance. See llm-notes.md.

See llm-notes.md for full context and rationale.

Asset Loading Issues

🐞 Issue: "Failed to process file: image [filename]"

Description:
Image assets fail to load, causing missing textures in the game.

Root Cause:

  1. Missing image files
  2. Incorrect path to assets
  3. Server permissions issues

Solution:

  1. Add proper error handling for asset loading
  2. Create fallback textures programmatically when assets can't be loaded
  3. Check that assets exist before trying to use them

Implementation:

// Handle missing image
this.load.on('loaderror', (file) => {
    if (file.key === 'texture') {
        console.warn('Failed to load texture, creating a fallback');
        // Create a fallback texture with graphics
        const graphics = this.make.graphics({x: 0, y: 0, add: false});
        graphics.fillStyle(0xff00ff, 1);
        graphics.fillCircle(32, 32, 25);
        graphics.generateTexture('texture', 64, 64);
    }
});