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Some playground improvements #4213

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b460632
Some playground improvements
Earlopain Aug 26, 2026
ffeef1e
Correctly handle multibyte chars in the playground
Earlopain Aug 26, 2026
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2 changes: 1 addition & 1 deletion doc/playground.css
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Original file line number Diff line number Diff line change
Expand Up @@ -268,7 +268,7 @@ main {
}

.tree-null {
color: var(--color-text-light);
color: #7e22ce;
font-style: italic;
}

Expand Down
62 changes: 39 additions & 23 deletions doc/playground.js
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,9 @@ const editorDiv = document.getElementById("editor");
const loading = document.getElementById("loading");
const toast = document.getElementById("toast");

const encoder = new TextEncoder();
const decoder = new TextDecoder();

// Load Prism WASM and Monaco, show error if either fails
let instance, monaco;
try {
Expand Down Expand Up @@ -115,15 +118,15 @@ end

// URL-safe base64 encode/decode (RFC 4648 §5)
function encodeSource(str) {
const bytes = new TextEncoder().encode(str);
const bytes = encoder.encode(str);
let binary = "";
for (let i = 0; i < bytes.length; i++) binary += String.fromCharCode(bytes[i]);
return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

function decodeSource(str) {
const padded = str.replace(/-/g, "+").replace(/_/g, "/") + "==".slice(0, (4 - str.length % 4) % 4);
return new TextDecoder().decode(Uint8Array.from(atob(padded), ch => ch.codePointAt(0)));
return decoder.decode(Uint8Array.from(atob(padded), ch => ch.codePointAt(0)));
}

// Read initial source from URL hash or use default
Expand Down Expand Up @@ -241,22 +244,30 @@ document.getElementById("expand-all").addEventListener("click", () => {
output.querySelectorAll(".tree-toggle").forEach(toggle => setToggleState(toggle, false));
});

// Convert byte offset to line:column using the source string
function offsetToLineCol(source, offset) {
// Convert byte offset to line:column using the utf8 bytes
function offsetToLineCol(utf8Bytes, offset) {
let line = 1, col = 0;
for (let i = 0; i < offset && i < source.length; i++) {
if (source[i] === "\n") { line++; col = 0; }
for (let i = 0; i < offset && i < utf8Bytes.length; i++) {
// Check for newline
if (utf8Bytes[i] === 10) { line++; col = 0; }
else { col++; }
}
return { line, col };
}


function formatLoc(source, loc) {
function formatLoc(utf8Bytes, loc, includeSlice) {
if (!loc || loc.startOffset === undefined) return null;
const start = offsetToLineCol(source, loc.startOffset);
const end = offsetToLineCol(source, loc.startOffset + loc.length);
return { start, end, text: `${start.line}:${start.col}-${end.line}:${end.col}` };
const start = offsetToLineCol(utf8Bytes, loc.startOffset);
const end = offsetToLineCol(utf8Bytes, loc.startOffset + loc.length);

let text = `${start.line}:${start.col}-${end.line}:${end.col}`;

if (includeSlice) {
const slice = decoder.decode(utf8Bytes.slice(loc.startOffset, loc.startOffset + loc.length));
text = `${text} = <span class="tree-string">${JSON.stringify(slice)}</span>`
}
return { start, end, text };
}

function locDataAttrs(loc) {
Expand Down Expand Up @@ -284,6 +295,10 @@ function isNode(value) {
return value && typeof value === "object" && !Array.isArray(value) && value.location && value.constructor && value.constructor.name !== "Object";
}

function isString(value) {
return value && typeof value === "object" && Object.hasOwn(value, "encoding")
}

// Get the node type name from the class name
function nodeType(node) {
return node.constructor?.name || "Unknown";
Expand Down Expand Up @@ -333,7 +348,7 @@ function hasChildNodes(fields, node) {
const CONNECTOR = { last: "└── ", mid: "├── ", lastPad: " ", midPad: "│ " };

// Build the AST tree as interactive HTML
function renderNode(node, source, prefix, isLast, isRoot) {
function renderNode(node, utf8Bytes, prefix, isLast, isRoot) {
if (!isNode(node)) return "";

const type = nodeType(node);
Expand All @@ -346,11 +361,11 @@ function renderNode(node, source, prefix, isLast, isRoot) {
if (!isRoot) html += `<span class="tree-connector" aria-hidden="true">${prefix}${isLast ? CONNECTOR.last : CONNECTOR.mid}</span>`;
if (foldable) html += `<button class="tree-toggle" aria-label="Toggle ${escapedType}">▼</button>`;

const loc = formatLoc(source, node.location);
const loc = formatLoc(utf8Bytes, node.location, false);
const locAttrs = locDataAttrs(loc);

html += `<span class="tree-type"${locAttrs}>@ ${escapedType}</span>`;
if (loc) html += ` <span class="tree-loc"${locAttrs}>(${loc.text})</span>`;
if (loc) html += ` <span class="tree-loc"${locAttrs}>(location: ${loc.text})</span>`;
html += `</div>`;

html += `<div class="tree-children" role="group">`;
Expand All @@ -375,7 +390,7 @@ function renderNode(node, source, prefix, isLast, isRoot) {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>: (${value.length} item${value.length === 1 ? "" : "s"})</div>`;
value.forEach((item, i) => {
if (isNode(item)) {
html += renderNode(item, source, fieldChildPrefix, i === value.length - 1);
html += renderNode(item, utf8Bytes, fieldChildPrefix, i === value.length - 1);
} else {
const itemConnector = i === value.length - 1 ? CONNECTOR.last : CONNECTOR.mid;
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${fieldChildPrefix}${itemConnector}</span><span class="tree-value">${escapeHtml(JSON.stringify(item))}</span></div>`;
Expand All @@ -384,14 +399,14 @@ function renderNode(node, source, prefix, isLast, isRoot) {
}
} else if (isNode(value)) {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>:</div>`;
html += renderNode(value, source, fieldChildPrefix, true);
html += renderNode(value, utf8Bytes, fieldChildPrefix, true);
} else if (typeof value === "object" && value.startOffset !== undefined) {
const fieldLoc = formatLoc(source, value);
const fieldLoc = formatLoc(utf8Bytes, value, true);
if (fieldLoc) {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>: <span class="tree-loc"${locDataAttrs(fieldLoc)}>${fieldLoc.text}</span></div>`;
}
} else if (typeof value === "string") {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>: <span class="tree-string">${escapeHtml(JSON.stringify(value))}</span></div>`;
} else if (isString(value)) {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>: <span class="tree-string">${escapeHtml(JSON.stringify(value.value))}</span></div>`;
} else {
html += `<div class="tree-node"><span class="tree-connector" aria-hidden="true">${childPrefix}${fieldConnector}</span><span class="tree-field">${escapeHtml(field)}</span>: <span class="tree-value">${escapeHtml(String(value))}</span></div>`;
}
Expand All @@ -407,8 +422,8 @@ function escapeHtml(str) {
}

// Render a single diagnostic line
function renderDiagnostic(source, item, kind) {
const loc = formatLoc(source, item.location);
function renderDiagnostic(utf8Bytes, item, kind) {
const loc = formatLoc(utf8Bytes, item.location, false);
const cssClass = kind === "Error" ? "error-text" : "warning-text";
return `<div class="diagnostics-line ${cssClass}"${locDataAttrs(loc)}>${kind}: ${escapeHtml(item.message)}${loc ? ` <span class="tree-loc">(${loc.text})</span>` : ""}</div>`;
}
Expand Down Expand Up @@ -453,9 +468,10 @@ function render() {

output.setAttribute("aria-labelledby", currentTab === "ast" ? "tab-ast" : "tab-diagnostics");

const utf8Bytes = encoder.encode(lastSource);
switch (currentTab) {
case "ast":
const tree = renderNode(lastResult.value, lastSource, "", true, true);
const tree = renderNode(lastResult.value, utf8Bytes, "", true, true);
output.innerHTML = tree
? `<div role="tree" aria-label="Abstract syntax tree">${tree}</div>`
: `<div class="empty-message error-text">${escapeHtml(lastResult.error || "Failed to parse.")}</div>`;
Expand All @@ -468,8 +484,8 @@ function render() {
output.innerHTML = `<div class="empty-message">No errors or warnings.</div>`;
} else {
let html = "";
for (const err of errors) html += renderDiagnostic(lastSource, err, "Error");
for (const warn of warnings) html += renderDiagnostic(lastSource, warn, "Warning");
for (const err of errors) html += renderDiagnostic(utf8Bytes, err, "Error");
for (const warn of warnings) html += renderDiagnostic(utf8Bytes, warn, "Warning");
output.innerHTML = html;
}
break;
Expand Down