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Diffdown is a real-time collaborative Markdown editor/previewer built on the AT Protocol
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1import {parser as baseParser} from "../dist/index.js"
2import {TreeFragment} from "@lezer/common"
3
4let parser = baseParser.configure({bufferLength: 2})
5
6let r = n => Math.floor(Math.random() * n)
7
8let tags = ["p", "ul", "li", "div", "span", "th", "tr", "body", "head", "title", "dd", "code", "em", "strong"]
9
10function randomDoc(size) {
11 let doc = ""
12 if (!r(5)) doc += "<!doctype html>"
13 let scope = []
14 for (let i = 0; i < size; i++) {
15 let sel = r(20)
16 if (sel < 5) {
17 let tag = tags[r(tags.length)]
18 doc += `<${tag}${r(2) ? " a=b" : ""}>`
19 scope.push(tag)
20 } else if (sel < 10 && scope.length) {
21 let name = scope.pop()
22 doc += `</${r(5) ? name : "div"}>`
23 } else if (sel == 10) {
24 doc += `<img>`
25 } else if (sel == 11) {
26 doc += "<script>a()</script>"
27 } else if (sel == 12) {
28 doc += r(2) ? "&" : "<!--@-->"
29 } else {
30 for (let i = r(6) + 1; i >= 0; i--)
31 doc += String.fromCharCode(97 + r(26))
32 }
33 }
34 while (scope.length) {
35 let name = scope.pop()
36 if (r(5)) doc += `</${name}>`
37 }
38 return doc
39}
40
41function check(doc, [tp, pos, txt], prevAST) {
42 let change = {fromA: pos, toA: pos, fromB: pos, toB: pos}, newDoc
43 if (tp == "insert") {
44 newDoc = doc.slice(0, pos) + txt + doc.slice(pos)
45 change.toA += txt.length
46 } else if (tp == "del") {
47 newDoc = doc.slice(0, pos) + doc.slice(pos + 1)
48 change.toB++
49 } else {
50 newDoc = doc.slice(0, pos) + txt + doc.slice(pos + 1)
51 change.toA += txt.length
52 change.toB++
53 }
54 let fragments = TreeFragment.applyChanges(TreeFragment.addTree(prevAST || parser.parse(doc)), [change], 2)
55 let ast = parser.parse(newDoc, fragments)
56 let orig = parser.parse(newDoc)
57 if (ast.toString() != orig.toString()) {
58 throw new Error(`Mismatch:\n ${ast}\nvs\n ${orig}\ndocument: ${
59 JSON.stringify(doc)}\naction: ${JSON.stringify([tp, pos, ch])}`)
60 }
61 return [newDoc, ast]
62}
63
64// Call this to just run random tests until a failing one is found.
65// Not directly called in the tests because there's a bunch of
66// circumstances in which uninteresting deviations in error recovery
67// will create differing parses, so results have to be manually
68// inspected.
69function generate() {
70 for (let count = 0, size = 2;; size = Math.min(40, size + 1)) {
71 let doc = randomDoc(size), prev = null
72 for (let i = 0; i < 2; i++) {
73 console.log("Attempt", ++count)
74 let action = [["del", "insert", "replace"][r(3)], r(doc.length - 1), "<>/piabc "[r(9)]]
75 ;([doc, prev] = check(doc, action, prev))
76 }
77 }
78}
79
80describe("Incremental parsing", () => {
81 it("doesn't get confused by reused opening tags", () => {
82 check("<code><code>mgnbni</code></code>", ["del", 29])
83 })
84
85 it("can handle a renamed opening tag after a self-closing", () => {
86 check("<p>one two three four five six seven<p>eight", ["replace", 37, "a"])
87 })
88
89 it("is okay with nameless elements", () => {
90 check("<body><code><img></code><>body>", ["replace", 14, ">"])
91 check("abcde<>fghij<", ["replace", 12, ">"])
92 })
93
94 it("doesn't get confused by an invalid close tag receiving a matching open tag", () => {
95 check("<div><p>foo</body>", ["insert", 0, "<body>"])
96 })
97})