xp-framework/rfc — Issue #200: XML API Rework
Author: thekid
Created: 2011-10-17 16:05:22+00:00
State: open
Labels: draft, framework

Scope of Change
====
The XML API will be extended to fully support markup-style XML documents.

Rationale
====
At the moment, certain information will be lost when loading and then
emitting an XML tree:

```php
Hello
World')->getSource();

//
// World
//

//
?>
```

Functionality
====
This loss of information is due to the fact that the above is transformed
to the following internal structure by the parser:

```
Node(name = 'html', content= 'World') {
Node(name = 'br')
}

```

The "Hello" is lost because any text encountered during parsing will be
set as the enclosing node's content, while any node will be added as
a child element. Then, when outputting the document again, the content
is appended first and after that any existing child.

Addressing this issue
----
Several new classes will be added to the xml package. They will all
implement the `xml.Element` interface:

```
* xml.Text
* xml.Comment
* xml.ProcessingInstruction

```

The `xml.Node` and `xml.Tree` class' `addChild()`
methods will be changed to accept any `xml.Element` implementation.

Finally, the parser will turn markup as seen before into the following
internal structure:

```
Node(name = 'html') {
Text(content = 'Hello'),
Node(name = 'br'),
Text(content = 'World')
}

```

The existing model with children will be used for the new implementation,
whereas the "content" member in a `xml.Node` and its accessors,
the `getContent()` and `setContent()` methods will be
deprecated.

BC: Constructor parameter "content"
----
A `Node` can be constructed with the content passed in its second
parameter:

```php
'http://example.com/'));
?>
```

The old behaviour would set the content member:

```
Node(name = 'a', content = 'Click', @{href = 'http://example.com/'})

```

The constructor will be changed to add a `Text` child node:

```
Node(name = 'a', @{href = 'http://example.com/'}) {
Text(content = 'Click')
}
?>
```

This will yield the same XML when `getSource()` is called.

CData
----
The `xml.CData` class will also implement the `Element`
interface.

PCData vs. Fragment
----
The `xml.PCData` class will also implement the `Element`
interface. It will be deprecated though, and replaced with a new class
called `xml.Fragment`.

I/O
----
The `xml.Tree`'s `fromFile()` and `fromString()`
methods will be deprecated in favor of the `xml.parser.TreeParser`
class.

```php
parse(new StreamInputSource(new FileInputStream('payload.xml')));
?>
```

The `getSource()` method will be deprecated in favor of the
`asXml()` method which will accept an `xml.io.OutputFormat`
instance.

```php
getSource(INDENT_DEFAULT);

// New
$xml= $tree->asXml(OutputFormat::$DEFAULT);

// Writing to any stream
$writer= new TreeWriter(new ...OutputStream(), OutputFormat::$DEFAULT);
$writer->write($tree);
?>
```

Security considerations
====
n/a

Speed impact
====
(TODO: Test)

Dependencies
====
None.

Related documents
====
Inspiration:
* http://dom4j.sourceforge.net/dom4j-1.6.1/index.html

Implementing patch:
* http://xp-framework.net/rfc/contrib/rfc0200.diff

Overlay:
* http://xp-framework.net/rfc/contrib/rfc0200.xar