chrome-devtools-frontend/front_end/ui/lit/strip-whitespace.ts

Chrome DevTools UI

// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import * as Platform from '../../core/platform/platform.js';
import * as Lit from '../../third_party/lit/lit.js';

const templates = new WeakMap<TemplateStringsArray, TemplateStringsArray>();

export function isLitDirective(value: unknown): value is {values: unknown[]} {
  return Boolean(typeof value === 'object' && value && '_$litDirective$' in value && 'values' in value);
}

export function html(strings: TemplateStringsArray, ...values: unknown[]): Lit.TemplateResult {
  let stripped = templates.get(strings);
  if (!stripped) {
    if (strings.some(s => s.includes('\n'))) {
      stripped = strip(strings);
    } else {
      stripped = strings;
    }
  }
  templates.set(strings, stripped);

  const escapeValue = (val: unknown): unknown => {
    if (typeof val === 'string') {
      return Platform.StringUtilities.safeEscapeUnicode(val);
    }
    if (Array.isArray(val)) {
      return val.map(escapeValue);
    }
    if (isLitDirective(val)) {
      val.values = val.values.map(escapeValue);
      return val;
    }
    return val;
  };
  const escapedValues = values.map(escapeValue);

  return Lit.html(stripped, ...escapedValues);
}

function strip(strings: TemplateStringsArray): TemplateStringsArray {
  let inTag = false;
  // Remove runs of whitespace following newline outside of tags.
  const stripped = strings.map(s => s.replace(/[<>]|\n\s*/g, s => {
    if (s === '<') {
      inTag = true;
    } else if (inTag && s === '>') {
      inTag = false;
    } else if (!inTag) {
      return '';
    }
    return s;
  })) as string[] & {raw: readonly string[]};
  stripped.raw = strings.raw;
  return stripped as TemplateStringsArray;
}