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🥅 Stricter types in apply() #40

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Jul 7, 2021
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Fixes: #37

Background

There are some corner cases that arise in the json0 library because -
given an object obj, and an array arr -these statements are both
true in JavaScript:

obj['123'] === obj[123]
arr['123'] === arr[123]

The fact that these statements are true can lead to some unexpected
silent transform() failures:

const op1 = [{p: ['a', '1', 0], si: 'hi'}]
const op2 = [{p: ['a', 1], lm: 0}]

json0.transform(op1, op2, 'left')

Actual result: [{p: ["a", 2, 0], si: "hi"}]
Expected result: [{p: ["a", 0, 0], si: "hi"}]

Solution

In order to prevent this, it's been decided that arrays should always
be indexed by number, and objects should always be indexed by
string.

This change enforces stricter type checks when calling apply(), and
now throws in the following cases:

  • When a number is used to key an object property:
    type.apply({'1': 'a'}, [{p:[1], od: 'a'}])
  • When a string is used to key an array property:
    type.apply(['a'], [{p:['0'], ld: 'a'}])
  • When adding a string to a number:
    type.apply(1, [{p:[], na: 'a}])
  • When adding a number to a string:
    type.apply('a', [{p:[], na: 1}])
  • When applying a string operation to a non-string:
    type.apply(1, [{p: [0], si: 'a'}])

Fixes: ottypes#37

# Background

There are some corner cases that arise in the `json0` library because -
given an object `obj`, and an array `arr` -these statements are both
`true` in JavaScript:

```js
obj['123'] === obj[123]
arr['123'] === arr[123]
```

The fact that these statements are true can lead to some unexpected
silent `transform()` failures:

```js
const op1 = [{p: ['a', '1', 0], si: 'hi'}]
const op2 = [{p: ['a', 1], lm: 0}]

json0.transform(op1, op2, 'left')
```

Actual result: `[{p: ["a", 2, 0], si: "hi"}]`
Expected result: `[{p: ["a", 0, 0], si: "hi"}]`

# Solution

In order to prevent this, it's been decided that arrays should *always*
be indexed by `number`, and objects should *always* be indexed by
`string`.

This change enforces stricter type checks when calling `apply()`, and
now throws in the following cases:

 - When a `number` is used to key an object property:
   `type.apply({'1': 'a'}, [{p:[1], od: 'a'}])`
 - When a `string` is used to key an array property:
   `type.apply(['a'], [{p:['0'], ld: 'a'}])`
 - When adding a `string` to a `number`:
   `type.apply(1, [{p:[], na: 'a}])`
 - When adding a `number` to a `string`:
   `type.apply('a', [{p:[], na: 1}])`
 - When applying a string operation to a non-string:
   `type.apply(1, [{p: [0], si: 'a'}])`
@nornagon nornagon merged commit afa00e0 into ottypes:master Jul 7, 2021
@alecgibson alecgibson deleted the stricter-types branch July 8, 2021 07:02
alecgibson added a commit to reedsy/json0 that referenced this pull request Jul 12, 2021
This change adds a `strict` flag to control whether we have the stricter
type checking introduced in ottypes#40

Strict mode will be off by default (to maintain compatibility with old
`json0` versions).

In order to add this flag, we also add a new `options` object to the
`type`. Strict mode is enabled on the type by setting the flag:

```js
type.options.strict = true
```

Note that `text0` will share the same options as `json0` (ie enabling
strict mode for `json0` also enables it for `text0`).

In this change we also tidy up some unused utility functions from a
previous commit.
@alecgibson alecgibson mentioned this pull request Jul 12, 2021
alecgibson added a commit to reedsy/json0 that referenced this pull request Jul 12, 2021
This change adds a `strict` flag to control whether we have the stricter
type checking introduced in ottypes#40

Strict mode will be off by default (to maintain compatibility with old
`json0` versions).

In order to add this flag, we also add a new `options` object to the
`type`. Strict mode is enabled on the type by setting the flag:

```js
type.options.strict = true
```

Note that `text0` will share the same options as `json0` (ie enabling
strict mode for `json0` also enables it for `text0`).

In this change we also tidy up some unused utility functions from a
previous commit.
alecgibson added a commit to reedsy/json0 that referenced this pull request Jul 13, 2021
This change removes unused utility functions that were accidentally
included in ottypes#40
alecgibson added a commit to share/sharedb that referenced this pull request Jul 14, 2021
`json0` recently merged a [breaking change][1] which enforces some
stricter type checking.

Apart from this stricter type checking, no other changes were made, so
any client that only ever submits well-formed ops should be able to
upgrade directly without any trouble.

However, if clients submitted some bad ops (that are no longer allowed
under the stricter checking), then `fetchSnapshot()` will fail when
trying to apply these ops to rebuild the snapshot.

This failure can be surprising if the only "bad" thing about the ops
was that they had [bad path types][2], because at the time when they
were submitted, the snapshot would have been correctly updated.

This change rescues from this particular failure by coercing paths into
the correct type: `number` for arrays, and `string` for objects. Note
that we use the exact same check for arrays and objects as `json0` to
ensure consistency.

Also note that we don't attempt to rescue new ops being submitted,
because these should correctly be rejected.

[1]: ottypes/json0#40
[2]: ottypes/json0#37
alecgibson added a commit to reedsy/json0 that referenced this pull request Dec 21, 2021
This change removes unused utility functions that were accidentally
included in ottypes#40
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Transforming ops with different use of integer/string indexes doesn't work
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