fix: make hash persistence unicode-safe by Pixel998 · Pull Request #367 · eslint/code-explorer

Pixel998 · 2026-03-28T21:17:13Z

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AI acknowledgment

I did not use AI to generate this PR.
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What is the purpose of this pull request?

This PR fixes explorer state persistence when the edited code contains Unicode characters. Previously, writing the shareable URL hash could throw InvalidCharacterError because the app used btoa(...) on a string containing characters outside the Latin1 range.

Steps to reproduce

Replace the editor contents with code containing non-Latin-1 characters, for example:

const π = "😀";

Open the browser console.
Observe this error when the app tries to write the hash:

InvalidCharacterError: Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.

What changes did you make? (Give an overview)

Updated hash persistence to use a versioned UTF-8-safe format for newly generated links while preserving support for legacy links.
Added e2e coverage.

Related Issues

I ran into this while working on eslint/markdown#640, where I noticed that emojis in the editor were no longer present after a reload.

Is there anything you'd like reviewers to focus on?

netlify · 2026-03-28T21:17:18Z

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amareshsm

LGTM. I’ll keep it open for another day in case anyone else wants to review.

Copilot

Pull request overview

Fixes explorer state persistence for Unicode-containing code by switching URL-hash serialization to a UTF-8-safe, versioned format while retaining backward compatibility with legacy hash links.

Changes:

Add v2: UTF-8-safe base64 encoding/decoding for persisted state stored in the URL hash, with legacy hash support preserved.
Harden hash reads by validating decoded payloads and falling back to localStorage when malformed.
Add Playwright e2e coverage for Unicode hash persistence, legacy link loading, and malformed-hash fallback.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/hooks/use-explorer.ts	Introduces versioned UTF-8-safe hash encoding/decoding and legacy decoding fallback to prevent `btoa` Unicode errors.
e2e-tests/persistence.test.ts	Adds e2e tests covering Unicode-safe hash persistence, legacy hash compatibility, and malformed hash fallback behavior.

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Copilot · 2026-04-02T08:45:46Z

src/hooks/use-explorer.ts

+const versionedHashPrefix = "v2:";
+


Using versionedHashPrefix = "v2:" means URLSearchParams will percent-encode the colon in the hash value (and standard base64 will also trigger percent-encoding for +, /, =). This inflates shared URLs and reduces the maximum amount of state that can fit in the hash. Consider a URL-safe prefix/format (e.g., base64url) to avoid extra encoding overhead.

Could using - instead of : be an option here, since it appears as - rather than %3A?

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Copilot · 2026-04-02T08:45:47Z

src/hooks/use-explorer.ts

+	let binary = "";
+
+	for (const byte of bytes) {
+		binary += String.fromCharCode(byte);
+	}
+


encodeHashStorageValue builds a binary string via repeated binary += String.fromCharCode(byte) concatenation. This allocates/concats once per byte and can become expensive for larger persisted payloads (the editor state can grow quite large). Consider a chunked conversion strategy or a Uint8Array→base64 helper to reduce intermediate string churn.

Suggested change

let binary = "";

for (const byte of bytes) {

binary += String.fromCharCode(byte);

}

const chunkSize = 0x8000; // 32KB chunks to limit argument list size

const chunks: string[] = [];

for (let i = 0; i < bytes.length; i += chunkSize) {

const chunk = bytes.subarray(i, i + chunkSize);

chunks.push(String.fromCharCode(...chunk));

}

const binary = chunks.join("");

I've tested this logic locally, but I'm not sure it really improves performance. Any further thoughts?

lumirlumir

LGTM, thanks. I don't have any further comments, but the Copilot review is worth a look. I'll leave this open to get another opinion before merging.

lumirlumir · 2026-04-02T09:00:02Z

src/hooks/use-explorer.ts

+const versionedHashPrefix = "v2:";
+


Could using - instead of : be an option here, since it appears as - rather than %3A?

To provide additional context for other reviewers, the URL is shown below:

If it is suffixed with -, the URL is shown below:

lumirlumir · 2026-04-02T09:10:57Z

src/hooks/use-explorer.ts

+	let binary = "";
+
+	for (const byte of bytes) {
+		binary += String.fromCharCode(byte);
+	}
+


I've tested this logic locally, but I'm not sure it really improves performance. Any further thoughts?

fix: make hash persistence unicode-safe

ff40263

eslint-github-bot bot added the bug Something isn't working label Mar 28, 2026

eslintbot added this to Triage Mar 28, 2026

github-project-automation bot moved this to Needs Triage in Triage Mar 28, 2026

amareshsm approved these changes Mar 29, 2026

View reviewed changes

amareshsm added the accepted There is consensus among the team that this change meets the criteria for inclusion label Mar 29, 2026

Pixel998 moved this from Needs Triage to Implementing in Triage Mar 30, 2026

lumirlumir self-requested a review April 2, 2026 07:40

lumirlumir moved this from Implementing to Second Review Needed in Triage Apr 2, 2026

lumirlumir requested a review from Copilot April 2, 2026 08:41

Copilot started reviewing on behalf of lumirlumir April 2, 2026 08:41 View session

Copilot AI reviewed Apr 2, 2026

View reviewed changes

lumirlumir approved these changes Apr 2, 2026

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lumirlumir requested a review from a team April 2, 2026 09:18

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fix: make hash persistence unicode-safe#367

fix: make hash persistence unicode-safe#367
Pixel998 wants to merge 1 commit intomainfrom
fix/unicode-safe-hash-persistence

Pixel998 commented Mar 28, 2026

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-	let binary = "";
-	for (const byte of bytes) {
-		binary += String.fromCharCode(byte);
-	}
+	const chunkSize = 0x8000; // 32KB chunks to limit argument list size
+	const chunks: string[] = [];
+	for (let i = 0; i < bytes.length; i += chunkSize) {
+		const chunk = bytes.subarray(i, i + chunkSize);
+		chunks.push(String.fromCharCode(...chunk));
+	}
+	const binary = chunks.join("");

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Pixel998 commented Mar 28, 2026

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What is the purpose of this pull request?

Steps to reproduce

What changes did you make? (Give an overview)

Related Issues

Is there anything you'd like reviewers to focus on?

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netlify bot commented Mar 28, 2026 •

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