What is meant by "document context" in JEP 198?

[Ethan McCue]

I suppose while I'm asking questions - what exactly are the parts of the
JDK making use of ad-hoc json? Maybe we could ship *something* as a
jdk.internal module for those use cases?

On Thu, Nov 24, 2022 at 8:55 PM Ethan McCue <ethan at mccue.dev> wrote:

> I'm reading JEP 198 and sketching out what an implementation could look
> like pursuant to this old conversation.
>
> https://mail.openjdk.org/pipermail/discuss/2020-April/005401.html
>
> My biggest question right now is what does the JEP mean exactly by
> "document context"
>
>
>    - Parsing APIs which allow a choice of parsing token stream, event
>    (includes document hierarchy context) stream, or immutable tree
>    representation views of JSON documents and data streams.
>
>
>
> So token stream I understand as something akin to
>
> sealed interface Token {
>     record StartArray() implements Token {}
>     record EndArray() implements Token {}
>     record StartObject() implements Token {}
>     record EndObject() implements Token {}
>     record Number(Json.Number value) implements Token {}
>     record String(Json.String value) implements Token {}
>     record True() implements Token {}
>     record False() implements Token {}
>     record Null() implements Token {}
> }
>
> Which matches up with the model in
> https://fasterxml.github.io/jackson-core/javadoc/2.7/com/fasterxml/jackson/core/JsonToken.html
>
> And an immutable tree representation as akin to
>
> sealed interface Json {
>     sealed interface Array extends Json, List<Json> ...
>     sealed interface Object extends Json, Map<java.lang.String, Json> ...
>     sealed abstract class Number extends java.lang.Number implements Json
> ...
>     sealed interface String extends Json, CharSequence ...
>     sealed interface Boolean ...
>     sealed interface Null extends Json ...
> }
>
> Which, ignoring the open questions of
> * Does the immutable tree need to be eagerly realized?
> * Do we need to wait for valhalla to land
> * Do we need to wait for full pattern matching to land
>
> (because they make me sad)
>
> I'm still unsure what information needs to be included in an "Event"
> stream that would constitute "document context". Is it pointers to parent
> collections? The current "Path"?
>
> sealed interface PathElement {
>     record Field(String fieldName) implements PathElement {}
>     record Index(int index) implements PathElement {}
> }
>
>
>
>
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