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mutation observer v2 (#206)

Browse Source 
There are some long-term issues in rrweb's mutation observer.

A scenario cause problem:
A list of DOM node: n1, n2, n3, n4, n5
Steps of modifying the nodes:
  1. remove n1, n2, n3, n4 sequentially
  2. append n4, n3, n2, n1 after n5 sequentially
Then we got the added node data like this:
  (id: n4, prev: null, next: n3  )
  (id: n3, prev: n4,   next: n2  )
  (id: n2, prev: n3,   next: n1  )
  (id: n1, prev: n2,   next: null)
The problem comes when we try to replay the first add node datum.
Since its prev node is null, we rely on its next sibling n3. But
n3 was not present at this moment, and in previous code, we fallback
to append n4 to the last of its parent node.

The solution is to defer the append of elements that missing
siblings. But it is also hard to tell which node is the first one
that needs to be appended.

Take a step back and rethink the design of the mutation observer,
we've found there are two implementations make things complicated.
1. We set the id to -1 when we seeing some nodes are not serialized yet.
2. We record both previous sibling and next sibling to determine the
position of the node.
But we can do better!
First, we can put nodes with un-serialized siblings
to a queue, and try to add it again later. Then we can just record the next
sibling as 'the single truth' so we can be sure which node is the last
one of its parent.

This patch has implemented the new observer strategy. Data recorded with
the new observer should no longer have any node with id -1. But for
compatibility consideration, we still keep some replayer code that helps
solve legacy data.
This commit is contained in:
yz-yu
2026-04-01 12:00:00 +08:00
committed by GitHub
parent 2a323da123
commit 43be602816
7 changed files with 351 additions and 165 deletions
Download Patch File Download Diff File Expand all files Collapse all files

384
test/__snapshots__/integration.test.ts.snap
View File

@@ -479,7 +479,6 @@ exports[`character-data 1`] = `
\\"adds\\": [
{
\\"parentId\\": 6,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -635,7 +634,6 @@ exports[`child-list 1`] = `
\\"adds\\": [
{
\\"parentId\\": 6,
\\"previousId\\": 7,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -2480,7 +2478,6 @@ exports[`move-node-1 1`] = `
\\"adds\\": [
{
\\"parentId\\": 6,
\\"previousId\\": 9,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -2492,7 +2489,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 11,
\\"previousId\\": null,
\\"nextId\\": 13,
\\"node\\": {
\\"type\\": 3,
@@ -2502,7 +2498,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 11,
\\"previousId\\": 12,
\\"nextId\\": 18,
\\"node\\": {
\\"type\\": 2,
@@ -2514,7 +2509,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": null,
\\"nextId\\": 15,
\\"node\\": {
\\"type\\": 3,
@@ -2524,7 +2518,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": 14,
\\"nextId\\": 17,
\\"node\\": {
\\"type\\": 2,
@@ -2536,7 +2529,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 15,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2546,7 +2538,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": 15,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2556,7 +2547,6 @@ exports[`move-node-1 1`] = `
},
{
\\"parentId\\": 11,
\\"previousId\\": 13,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2748,7 +2738,6 @@ exports[`move-node-2 1`] = `
\\"adds\\": [
{
\\"parentId\\": 11,
\\"previousId\\": null,
\\"nextId\\": 13,
\\"node\\": {
\\"type\\": 3,
@@ -2758,7 +2747,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 11,
\\"previousId\\": 12,
\\"nextId\\": 18,
\\"node\\": {
\\"type\\": 2,
@@ -2770,7 +2758,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": null,
\\"nextId\\": 15,
\\"node\\": {
\\"type\\": 3,
@@ -2780,7 +2767,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": 14,
\\"nextId\\": 17,
\\"node\\": {
\\"type\\": 2,
@@ -2792,7 +2778,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 15,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2802,7 +2787,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 13,
\\"previousId\\": 15,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2812,7 +2796,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 11,
\\"previousId\\": 13,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -2822,7 +2805,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 4,
\\"previousId\\": 22,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -2834,7 +2816,6 @@ exports[`move-node-2 1`] = `
},
{
\\"parentId\\": 23,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -3804,7 +3785,7 @@ exports[`select2 1`] = `
}
},
{
\\"id\\": 75,
\\"id\\": 70,
\\"attributes\\": {
\\"style\\": \\"\\"
}
@@ -3823,7 +3804,7 @@ exports[`select2 1`] = `
}
},
{
\\"id\\": 67,
\\"id\\": 72,
\\"attributes\\": {
\\"class\\": \\"select2-results-dept-0 select2-result select2-result-selectable select2-highlighted\\"
}
@@ -3842,7 +3823,6 @@ exports[`select2 1`] = `
\\"adds\\": [
{
\\"parentId\\": 25,
\\"previousId\\": null,
\\"nextId\\": 34,
\\"node\\": {
\\"type\\": 2,
@@ -3858,7 +3838,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 26,
\\"previousId\\": null,
\\"nextId\\": 28,
\\"node\\": {
\\"type\\": 3,
@@ -3868,7 +3847,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 26,
\\"previousId\\": 27,
\\"nextId\\": 30,
\\"node\\": {
\\"type\\": 2,
@@ -3883,7 +3861,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 28,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -3893,7 +3870,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 26,
\\"previousId\\": 28,
\\"nextId\\": 31,
\\"node\\": {
\\"type\\": 2,
@@ -3907,7 +3883,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 26,
\\"previousId\\": 30,
\\"nextId\\": 32,
\\"node\\": {
\\"type\\": 3,
@@ -3917,7 +3892,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 26,
\\"previousId\\": 31,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -3932,7 +3906,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 32,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -3946,7 +3919,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 18,
\\"previousId\\": -1,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -3961,7 +3933,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 36,
\\"previousId\\": null,
\\"nextId\\": 38,
\\"node\\": {
\\"type\\": 3,
@@ -3971,7 +3942,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 36,
\\"previousId\\": 37,
\\"nextId\\": 44,
\\"node\\": {
\\"type\\": 2,
@@ -3985,7 +3955,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 38,
\\"previousId\\": null,
\\"nextId\\": 40,
\\"node\\": {
\\"type\\": 3,
@@ -3995,7 +3964,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 38,
\\"previousId\\": 39,
\\"nextId\\": 41,
\\"node\\": {
\\"type\\": 2,
@@ -4010,7 +3978,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 38,
\\"previousId\\": 40,
\\"nextId\\": 42,
\\"node\\": {
\\"type\\": 3,
@@ -4020,7 +3987,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 38,
\\"previousId\\": 41,
\\"nextId\\": 43,
\\"node\\": {
\\"type\\": 2,
@@ -4046,7 +4012,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 38,
\\"previousId\\": 42,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -4056,7 +4021,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 36,
\\"previousId\\": 38,
\\"nextId\\": 45,
\\"node\\": {
\\"type\\": 3,
@@ -4066,7 +4030,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 36,
\\"previousId\\": 44,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -4082,62 +4045,6 @@ exports[`select2 1`] = `
},
{
\\"parentId\\": 45,
\\"previousId\\": null,
\\"nextId\\": -1,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {
\\"class\\": \\"select2-results-dept-0 select2-result select2-result-selectable select2-highlighted\\",
\\"role\\": \\"presentation\\"
},
\\"childNodes\\": [],
\\"id\\": 67
}
},
{
\\"parentId\\": 67,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"div\\",
\\"attributes\\": {
\\"class\\": \\"select2-result-label\\",
\\"id\\": \\"select2-result-label-2\\",
\\"role\\": \\"option\\"
},
\\"childNodes\\": [],
\\"id\\": 68
}
},
{
\\"parentId\\": 68,
\\"previousId\\": null,
\\"nextId\\": -1,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"span\\",
\\"attributes\\": {
\\"class\\": \\"select2-match\\"
},
\\"childNodes\\": [],
\\"id\\": 69
}
},
{
\\"parentId\\": 68,
\\"previousId\\": 69,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
\\"textContent\\": \\"A\\",
\\"id\\": 70
}
},
{
\\"parentId\\": 45,
\\"previousId\\": 67,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -4147,12 +4054,11 @@ exports[`select2 1`] = `
\\"role\\": \\"presentation\\"
},
\\"childNodes\\": [],
\\"id\\": 71
\\"id\\": 67
}
},
{
\\"parentId\\": 71,
\\"previousId\\": null,
\\"parentId\\": 67,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -4163,36 +4069,20 @@ exports[`select2 1`] = `
\\"role\\": \\"option\\"
},
\\"childNodes\\": [],
\\"id\\": 72
\\"id\\": 68
}
},
{
\\"parentId\\": 72,
\\"previousId\\": null,
\\"nextId\\": -1,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"span\\",
\\"attributes\\": {
\\"class\\": \\"select2-match\\"
},
\\"childNodes\\": [],
\\"id\\": 73
}
},
{
\\"parentId\\": 72,
\\"previousId\\": 73,
\\"parentId\\": 68,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
\\"textContent\\": \\"B\\",
\\"id\\": 74
\\"id\\": 69
}
},
{
\\"parentId\\": 18,
\\"previousId\\": 66,
\\"nextId\\": 36,
\\"node\\": {
\\"type\\": 2,
@@ -4203,16 +4093,79 @@ exports[`select2 1`] = `
\\"style\\": \\"\\"
},
\\"childNodes\\": [],
\\"id\\": 75
\\"id\\": 70
}
},
{
\\"parentId\\": 62,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
\\"textContent\\": \\"2 results are available, use up and down arrow keys to navigate.\\",
\\"id\\": 71
}
},
{
\\"parentId\\": 45,
\\"nextId\\": 67,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {
\\"class\\": \\"select2-results-dept-0 select2-result select2-result-selectable select2-highlighted\\",
\\"role\\": \\"presentation\\"
},
\\"childNodes\\": [],
\\"id\\": 72
}
},
{
\\"parentId\\": 72,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"div\\",
\\"attributes\\": {
\\"class\\": \\"select2-result-label\\",
\\"id\\": \\"select2-result-label-2\\",
\\"role\\": \\"option\\"
},
\\"childNodes\\": [],
\\"id\\": 73
}
},
{
\\"parentId\\": 73,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
\\"textContent\\": \\"A\\",
\\"id\\": 74
}
},
{
\\"parentId\\": 68,
\\"nextId\\": 69,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"span\\",
\\"attributes\\": {
\\"class\\": \\"select2-match\\"
},
\\"childNodes\\": [],
\\"id\\": 75
}
},
{
\\"parentId\\": 73,
\\"nextId\\": 74,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"span\\",
\\"attributes\\": {
\\"class\\": \\"select2-match\\"
},
\\"childNodes\\": [],
\\"id\\": 76
}
}
@@ -4224,7 +4177,7 @@ exports[`select2 1`] = `
\\"data\\": {
\\"source\\": 2,
\\"type\\": 0,
\\"id\\": 75
\\"id\\": 70
}
},
{
@@ -4250,7 +4203,7 @@ exports[`select2 1`] = `
\\"data\\": {
\\"source\\": 2,
\\"type\\": 1,
\\"id\\": 75
\\"id\\": 70
}
},
{
@@ -4276,7 +4229,7 @@ exports[`select2 1`] = `
\\"texts\\": [],
\\"attributes\\": [
{
\\"id\\": 75,
\\"id\\": 70,
\\"attributes\\": {
\\"style\\": \\"display: none;\\"
}
@@ -4309,21 +4262,20 @@ exports[`select2 1`] = `
\\"removes\\": [
{
\\"parentId\\": 18,
\\"id\\": 75
\\"id\\": 70
},
{
\\"parentId\\": 45,
\\"id\\": 72
},
{
\\"parentId\\": 45,
\\"id\\": 67
},
{
\\"parentId\\": 45,
\\"id\\": 71
}
],
\\"adds\\": [
{
\\"parentId\\": 18,
\\"previousId\\": 66,
\\"nextId\\": 36,
\\"node\\": {
\\"type\\": 2,
@@ -4334,7 +4286,7 @@ exports[`select2 1`] = `
\\"style\\": \\"display: none;\\"
},
\\"childNodes\\": [],
\\"id\\": 75
\\"id\\": 70
}
}
]
@@ -4350,3 +4302,177 @@ exports[`select2 1`] = `
}
]"
`;
exports[`serialize-before-record 1`] = `
"[
{
\\"type\\": 0,
\\"data\\": {}
},
{
\\"type\\": 1,
\\"data\\": {}
},
{
\\"type\\": 4,
\\"data\\": {
\\"href\\": \\"about:blank\\",
\\"width\\": 1920,
\\"height\\": 1080
}
},
{
\\"type\\": 2,
\\"data\\": {
\\"node\\": {
\\"type\\": 0,
\\"childNodes\\": [
{
\\"type\\": 2,
\\"tagName\\": \\"html\\",
\\"attributes\\": {},
\\"childNodes\\": [
{
\\"type\\": 2,
\\"tagName\\": \\"head\\",
\\"attributes\\": {},
\\"childNodes\\": [],
\\"id\\": 3
},
{
\\"type\\": 2,
\\"tagName\\": \\"body\\",
\\"attributes\\": {},
\\"childNodes\\": [
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n \\",
\\"id\\": 5
},
{
\\"type\\": 2,
\\"tagName\\": \\"p\\",
\\"attributes\\": {},
\\"childNodes\\": [
{
\\"type\\": 3,
\\"textContent\\": \\"mutation observer\\",
\\"id\\": 7
}
],
\\"id\\": 6
},
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n \\",
\\"id\\": 8
},
{
\\"type\\": 2,
\\"tagName\\": \\"ul\\",
\\"attributes\\": {},
\\"childNodes\\": [
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n \\",
\\"id\\": 10
},
{
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {},
\\"childNodes\\": [],
\\"id\\": 11
},
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n \\",
\\"id\\": 12
}
],
\\"id\\": 9
},
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n\\\\n \\",
\\"id\\": 13
},
{
\\"type\\": 2,
\\"tagName\\": \\"script\\",
\\"attributes\\": {},
\\"childNodes\\": [
{
\\"type\\": 3,
\\"textContent\\": \\"SCRIPT_PLACEHOLDER\\",
\\"id\\": 15
}
],
\\"id\\": 14
},
{
\\"type\\": 3,
\\"textContent\\": \\"\\\\n \\\\n \\",
\\"id\\": 16
}
],
\\"id\\": 4
}
],
\\"id\\": 2
}
],
\\"id\\": 1
},
\\"initialOffset\\": {
\\"left\\": 0,
\\"top\\": 0
}
}
},
{
\\"type\\": 3,
\\"data\\": {
\\"source\\": 0,
\\"texts\\": [],
\\"attributes\\": [],
\\"removes\\": [],
\\"adds\\": [
{
\\"parentId\\": 9,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {},
\\"childNodes\\": [],
\\"id\\": 17
}
},
{
\\"parentId\\": 9,
\\"nextId\\": 17,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {},
\\"childNodes\\": [],
\\"id\\": 18
}
},
{
\\"parentId\\": 9,
\\"nextId\\": 18,
\\"node\\": {
\\"type\\": 2,
\\"tagName\\": \\"li\\",
\\"attributes\\": {},
\\"childNodes\\": [],
\\"id\\": 19
}
}
]
}
}
]"
`;

6
test/__snapshots__/record.test.ts.snap
View File

@@ -82,7 +82,6 @@ exports[`async-checkout 1`] = `
\\"adds\\": [
{
\\"parentId\\": 4,
\\"previousId\\": 7,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -94,7 +93,6 @@ exports[`async-checkout 1`] = `
},
{
\\"parentId\\": 8,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -117,7 +115,6 @@ exports[`async-checkout 1`] = `
\\"adds\\": [
{
\\"parentId\\": 9,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -220,7 +217,6 @@ exports[`async-checkout 1`] = `
\\"adds\\": [
{
\\"parentId\\": 4,
\\"previousId\\": 8,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,
@@ -232,7 +228,6 @@ exports[`async-checkout 1`] = `
},
{
\\"parentId\\": 9,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 3,
@@ -409,7 +404,6 @@ exports[`stylesheet-rules 1`] = `
\\"adds\\": [
{
\\"parentId\\": 3,
\\"previousId\\": null,
\\"nextId\\": null,
\\"node\\": {
\\"type\\": 2,