6 /**
7 * @import {
8 * Create,
9+ * Extension,
10 * FullNormalizedExtension,
11 * InitialConstruct,
12 * ParseContext,
14 import * as defaultConstructs from './constructs.js'
15 import {createTokenizer} from './create-tokenizer.js'
17+/** @type {WeakMap<ReadonlyArray<Extension>, FullNormalizedExtension>} */
18+const combined = new WeakMap()
19+/** @type {Array<Extension>} */
20+const noExtensions = []
21+
22 /**
23 * @param {ParseOptions | null | undefined} [options]
24 * Configuration (optional).
26 */
27 export function parse(options) {
28 const settings = options || {}
29- const constructs = /** @type {FullNormalizedExtension} */ (
30- combineExtensions([defaultConstructs, ...(settings.extensions || [])])
31- )
32+ const extensions = settings.extensions || noExtensions
33+ // Parsers are made per document; their constructs only depend on the extensions, which must
34+ // not change once parsed with (unified fills them while attaching plugins, before parsing).
35+ let constructs = combined.get(extensions)
36+ if (!constructs) {
37+ constructs = /** @type {FullNormalizedExtension} */ (
38+ combineExtensions([defaultConstructs, ...extensions])
39+ )
40+ combined.set(extensions, constructs)
41+ }
43 /** @type {ParseContext} */
44 const parser = {
50 /**
51 * @import {
52 * Create,
53+ * Extension,
54 * FullNormalizedExtension,
55 * InitialConstruct,
56 * ParseContext,
58 import * as defaultConstructs from './constructs.js';
59 import { createTokenizer } from './create-tokenizer.js';
61+/** @type {WeakMap<ReadonlyArray<Extension>, FullNormalizedExtension>} */
62+const combined = new WeakMap();
63+/** @type {Array<Extension>} */
64+const noExtensions = [];
65+
66 /**
67 * @param {ParseOptions | null | undefined} [options]
68 * Configuration (optional).
70 */
71 export function parse(options) {
72 const settings = options || {};
73- const constructs = /** @type {FullNormalizedExtension} */
74- combineExtensions([defaultConstructs, ...(settings.extensions || [])]);
75+ const extensions = settings.extensions || noExtensions;
76+ // Parsers are made per document; their constructs only depend on the extensions, which must
77+ // not change once parsed with (unified fills them while attaching plugins, before parsing).
78+ let constructs = combined.get(extensions);
79+ if (!constructs) {
80+ constructs = /** @type {FullNormalizedExtension} */ (
81+ combineExtensions([defaultConstructs, ...extensions])
82+ );
83+ combined.set(extensions, constructs);
84+ }
86 /** @type {ParseContext} */
87 const parser = {