lit-html/development/static.js

/**
 * @license
 * Copyright 2020 Google LLC
 * SPDX-License-Identifier: BSD-3-Clause
 */
// Any new exports need to be added to the export statement in
// `packages/lit/src/index.all.ts`.
import { html as coreHtml, svg as coreSvg } from './lit-html.js';
/**
 * Prevents JSON injection attacks.
 *
 * The goals of this brand:
 *   1) fast to check
 *   2) code is small on the wire
 *   3) multiple versions of Lit in a single page will all produce mutually
 *      interoperable StaticValues
 *   4) normal JSON.parse (without an unusual reviver) can not produce a
 *      StaticValue
 *
 * Symbols satisfy (1), (2), and (4). We use Symbol.for to satisfy (3), but
 * we don't care about the key, so we break ties via (2) and use the empty
 * string.
 */
const brand = Symbol.for('');
/** Safely extracts the string part of a StaticValue. */
const unwrapStaticValue = (value) => {
    if (value?.r !== brand) {
        return undefined;
    }
    return value?.['_$litStatic$'];
};
/**
 * Wraps a string so that it behaves like part of the static template
 * strings instead of a dynamic value.
 *
 * Users must take care to ensure that adding the static string to the template
 * results in well-formed HTML, or else templates may break unexpectedly.
 *
 * Note that this function is unsafe to use on untrusted content, as it will be
 * directly parsed into HTML. Do not pass user input to this function
 * without sanitizing it.
 *
 * Static values can be changed, but they will cause a complete re-render
 * since they effectively create a new template.
 */
export const unsafeStatic = (value) => ({
    ['_$litStatic$']: value,
    r: brand,
});
const textFromStatic = (value) => {
    if (value['_$litStatic$'] !== undefined) {
        return value['_$litStatic$'];
    }
    else {
        throw new Error(`Value passed to 'literal' function must be a 'literal' result: ${value}. Use 'unsafeStatic' to pass non-literal values, but
            take care to ensure page security.`);
    }
};
/**
 * Tags a string literal so that it behaves like part of the static template
 * strings instead of a dynamic value.
 *
 * The only values that may be used in template expressions are other tagged
 * `literal` results or `unsafeStatic` values (note that untrusted content
 * should never be passed to `unsafeStatic`).
 *
 * Users must take care to ensure that adding the static string to the template
 * results in well-formed HTML, or else templates may break unexpectedly.
 *
 * Static values can be changed, but they will cause a complete re-render since
 * they effectively create a new template.
 */
export const literal = (strings, ...values) => ({
    ['_$litStatic$']: values.reduce((acc, v, idx) => acc + textFromStatic(v) + strings[idx + 1], strings[0]),
    r: brand,
});
const stringsCache = new Map();
/**
 * Wraps a lit-html template tag (`html` or `svg`) to add static value support.
 */
export const withStatic = (coreTag) => (strings, ...values) => {
    const l = values.length;
    let staticValue;
    let dynamicValue;
    const staticStrings = [];
    const dynamicValues = [];
    let i = 0;
    let hasStatics = false;
    let s;
    while (i < l) {
        s = strings[i];
        // Collect any unsafeStatic values, and their following template strings
        // so that we treat a run of template strings and unsafe static values as
        // a single template string.
        while (i < l &&
            ((dynamicValue = values[i]),
                (staticValue = unwrapStaticValue(dynamicValue))) !== undefined) {
            s += staticValue + strings[++i];
            hasStatics = true;
        }
        // If the last value is static, we don't need to push it.
        if (i !== l) {
            dynamicValues.push(dynamicValue);
        }
        staticStrings.push(s);
        i++;
    }
    // If the last value isn't static (which would have consumed the last
    // string), then we need to add the last string.
    if (i === l) {
        staticStrings.push(strings[l]);
    }
    if (hasStatics) {
        const key = staticStrings.join('$$lit$$');
        strings = stringsCache.get(key);
        if (strings === undefined) {
            // Beware: in general this pattern is unsafe, and doing so may bypass
            // lit's security checks and allow an attacker to execute arbitrary
            // code and inject arbitrary content.
            // eslint-disable-next-line @typescript-eslint/no-explicit-any
            staticStrings.raw = staticStrings;
            stringsCache.set(key, (strings = staticStrings));
        }
        values = dynamicValues;
    }
    return coreTag(strings, ...values);
};
/**
 * Interprets a template literal as an HTML template that can efficiently
 * render to and update a container.
 *
 * Includes static value support from `lit-html/static.js`.
 */
export const html = withStatic(coreHtml);
/**
 * Interprets a template literal as an SVG template that can efficiently
 * render to and update a container.
 *
 * Includes static value support from `lit-html/static.js`.
 */
export const svg = withStatic(coreSvg);
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