sindresorhus/eslint-plugin-unicorn

Rule proposal: `no-canvas-to-image`

Closed

#1,271 opened on May 13, 2021

View on GitHubContributor guide
 (1 comment) (3 reactions) (0 assignees)JavaScript (468 forks)user submission
help wantednew rule

Repository metrics

Stars
 (5,022 stars)
PR merge metrics
 (Avg merge 1d 16h) (399 merged PRs in 30d)

Description

Many people don't know CanvasRenderingContext2D.drawImage() accept HTMLCanvasElement as CanvasImageSource

Fail

const image = await loadImage(canvas1.toDataURL());
context2.drawImage(image);

const imageData = context1.getImageData();
context2.putImageData(imageData);

Pass

context2.drawImage(canvas1)

Contributor guide

Research direction
Implement a new ESLint rule 'no canvas to image' that detects inefficient canvas to image conversions. Study existing rules in the eslint plugin unicorn repository (e.g., in the 'rules' folder) to understand the pattern. Create a rule file that uses AST selectors to find calls like `canvas.toDataURL()` used in `loadImage` or `new Image()`. Write corresponding tests in the 'test' folder. The rule should suggest using `drawImage(canvas)` directly. Base your implementation on the structure of other rules that check for API misuse.
Tech stack
javascript
Domain
frontendperformance
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
understanding of ESLint plugin developmentfamiliarity with AST manipulation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65