✨ Add presence support #48
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alecgibson
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ericyhwang
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Dec 29, 2021
lib/json0.js
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| // Deletions should be treated as insertions: transforming | ||
| // by them should result in a no-op (null presence), so | ||
| // let's just pretend that deletions are oi to get the |
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The "pretend that deletions are oi" comment is confusing on first read, would be worth elaborating a bit more on how that works
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👍🏼 I've tried to clarify
README.md
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| The format of a `json0` presence object follows a similar syntax to its ops: | ||
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| [{p: ['key', 123], v: 0}] |
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From the implementation, this shouldn't have an array wrapping it?
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Yup, docs were wrong. I've updated.
lib/json0.js
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| for (var i = 0; i < op.length; i++) { | ||
| var component = op[i]; | ||
| // Set side as 'right' because we always want the op to win ties, since | ||
| // our transformed "op" isn't really an op |
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Would be worth mentioning that for json0, this is just to handle subpath changes as a result of list move, insert, delete.
lib/json0.js
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| delete component.od; | ||
| } | ||
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| if ('ld' in component) { |
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I'm curious if this breaks the json.transform(transformed, [component], 'right') lower down, if you, say, have presence on index 4 of an array and do a ld on index 2.
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Great catch. Fixed with a path check.
alecgibson
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Dec 29, 2021
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This change adds support for the `transformPresence()` method that
[`sharedb` uses][1].
We add support for both `text0` and `json0`.
`text0`
-------
The `text0` implementation leans on the existing
[`transformPosition`][2], and takes its form and tests from
[`rich-text`][3].
Its shape takes the form:
```js
{
index: 3,
length: 5,
}
```
Where:
- `index` is the cursor position
- `length` is the selection length (`0` for a collapsed selection)
`json0`
-------
The `json0` implementation has limited functionality because of the
limitations of the `json0` type itself: we handle list moves `lm`, but
cannot infer any information when moving objects around the tree,
because the `oi` and `od` operations are destructive.
However, it will attempt to transform embedded subtypes that support
presence.
Its shape takes the form:
```js
{
p: ['key', 123],
v: {},
}
```
Where:
- `p` is the path to the client's position within the document
- `v` is the presence value
The presence value `v` can take any arbitrary value (in simple cases it
may even be omitted entirely).
The exception to this is when using subtypes, where `v` should take the
presence shape defined by the subtype. For example, when using `text0`:
```js
{
p: ['key'],
v: {index: 5, length: 0},
}
```
[1]: share/sharedb#322
[2]: https://github.com/ottypes/json0/blob/90a3ae26364c4fa3b19b6df34dad46707a704421/lib/text0.js#L147
[3]: ottypes/rich-text#32
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Fixes #30
This change adds support for the
transformPresence()method thatsharedbuses.We add support for both
text0andjson0.text0The
text0implementation leans on the existingtransformPosition, and takes its form and tests fromrich-text.Its shape takes the form:
Where:
indexis the cursor positionlengthis the selection length (0for a collapsed selection)json0The
json0implementation has limited functionality because of thelimitations of the
json0type itself: we handle list moveslm, butcannot infer any information when moving objects around the tree,
because the
oiandodoperations are destructive.However, it will attempt to transform embedded subtypes that support
presence.
Its shape takes the form:
Where:
pis the path to the client's position within the documentvis the presence valueThe presence value
vcan take any arbitrary value (in simple cases itmay even be omitted entirely).
The exception to this is when using subtypes, where
vshould take thepresence shape defined by the subtype. For example, when using
text0: