Dom Tree about xml-rs

[linkmauve]

In addition to xmltree-rs mentioned above, we now have https://crates.io/crates/minidom and https://crates.io/crates/elementtree, I’d suggest closing this issue as out of scope.

[netvl]

Yes, you're correct on that the library needs a DOM tree building. I want just to finish XML writing first.

As for your suggestions, I think that encapsulating existing events is a no-go. Events and DOM trees are way too different. A separate data type will be needed.

One of the best XML DOM libraries I've ever used is JDOM2. It may be used as a source of inspiration. It is a Java library, so its approach can't be used directly in Rust, though; I believe we have the same troubles here as the Servo team has with HTML DOM nodes.

I was also thinking about using a zipper structure. It may be more convenient to use given Rust ownership semantics and more extensive functional capabilities, but it may have the same problem with bidirectional references like in a regular DOM tree. This requires additional research.

[masklinn]

@netvl not all DOMs have bidi links, and though bidirectional parent/child links are useful much can already be done with just parent -> child.

For instance Python's ElementTree API is reasonably well regarded and provides no child -> parent link (although lxml reimplementation does extend it with one such link, and numerous others, that capability might be added later on if somebody figures out how, alternatively the first DOM could be called Simple* and provide only a basic tree-ish API with a simple costs profile, with the ability to either extend it later on or add a separate more featureful treeish).

Servo must implement a W3C DOM with all its requirements and java-ish-based semantics, xml-rs doesn't necessarily have to.

[netvl]

@masklinn, you're right, of course. I think that at first something like Json ADT will do fine.

[zonyitoo]

I think the DOM structure could be

// Attribute could be represented as a Map
type OwnedAttribute = BTreeMap<OwnedName, String>;

struct Node {
    parent: Weak<Node>,
    data: NodeData,
}

enum NodeData {
    Element {
        name: OwnedName,
        attributes: OwnedAttribute,
        namespace: Rc<Namespace>,
        children: DList<Rc<Node>>,
    },
    Text(String),
    CData(String),
    Comment(String),
    ProcInst {
        encoding: Encoding,
        target: String,
        version: Version,
    }
}

struct Document {
    root: Rc<Node>,
    encoding: Encoding,
    namespace: Rc<Namespace>,
}

[rminderhoud]

This crate provides this functionality and is built on top of xml-rs: https://github.com/eminence/xmltree-rs

[kornelski]

I'll leave DOM construction to other crates.