silverstripe-framework/docs/en/04_Changelogs/4.2.0.md

# 4.2.0

## Overview {#overview}

 * Disable session-based stage setting in `Versioned` (see [#1578](https://github.com/silverstripe/silverstripe-cms/issues/1578))
 * Deprecated `FunctionalTest::useDraftSite()`. You should use querystring args instead for setting stage.

## Upgrading {#upgrading}

### App folder name

The standard 'mysite' code naming convention has changed in 4.2. Although existing sites can continue
to use 'mysite/code` to store their base project code, the recommendation and new default is to
store code in `app/src`.

Additionally, we reinforce the recommendation to use psr-4 autoloading in your project to speed up
class loading.

In order to upgrade a site to use `app/src` folder:

 - Rename the folder `mysite` to `app` and `code` to `src`.
 - Update your `app/_config/mysite.yml` config to the below:

```yaml
---
Name: myproject
---
SilverStripe\Core\Manifest\ModuleManifest:
  project: app
```

 - add psr-4 for your root project files and namespace. An example `composer.json` below
   shows how this might look:

```json
{
    "autoload": {
        "psr-4": {
            "TractorCow\\MyWebsite\\": "app/src/"
        },
        "classmap": [
            "app/src/Page.php",
            "app/src/PageController.php"
        ]
    }
}
```

 - Ensure you flush your site with `?flush=all`
 
Note: In 5.0 the app folder will be fixed to `app` and cannot be soft-coded via `mysite.yml`

### Disable session-based stage setting

When viewing a versioned record (usually pages) in "draft" mode,
SilverStripe used to record this mode in the session for further requests.
This has the advantage of transparently working on XHR and API requests,
as well as authenticated users navigating through other views.

These subsequent requests no longer carried an explicit `stage` query parameter,
which meant the same URL might show draft or live content depending on your session state.
While most HTTP caching layers deal gracefully with this variation by disabling
any caching when a session cookie is present, there is a small chance
that draft content is exposed to unauthenticated users for the lifetime of the cache.

Due to this potential risk for information leakage,
we have decided to only rely on the `stage` query parameter.
If you are consistently using the built-in `SiteTree->Link()`
and `Controller->Link()` methods to get URLs, this change likely won't affect you. 

If you are manually concatenating URLs to SilverStripe controllers
rather than through their `Link()` methods (in custom PHP or JavaScript),
or have implemented your own `Link()` methods on controllers exposing
versioned objects, you'll need to check your business logic.

Alternatively, you can opt-out of this security feature via YAML configuration:

```yml
SilverStripe\Versioned\Versioned:
  use_session: true
```

Check our [versioning docs](/developer_guides/model/versioning#controllers)
for more details.

### New Versioned API

The following methods have been added to [api:SilverStripe\Versioned\Versioned] class:

 * `withVersionedMode()` Allows users to execute a closure which may internally modify
   the current stage, but will guarantee these changes are reverted safely on return.
   Helpful when temporarily performing a task in another stage or view mode.
 * `get_draft_site_secured()` / `set_draft_site_secured()` Enables the explicit toggle
   of draft site security. By setting this to false, you can expose a draft mode to
   unauthenticated users. Replaces `unsecuredDraftSite` session var.
 * `get_default_reading_mode()` / `set_default_reading_mode()` The default reading
  mode is now configurable. Any non-default reading mode must have querystring args
  to be visible. This will be the mode choosen for requests that do not have these args.
  Note that the default mode for CMS is now draft, but is live on the frontend.

A new class [api:SilverStripe\Versioned\ReadingMode] has also been added to assist with
conversion of the reading mode between:
 - Reading mode string
 - DataQuery parameters
 - Querystring parameters

### Link tracking

SiteTreeLinkTracking has been split and refactored into two extensions, and now
no longer applies exclusively to `HTMLContent` areas on `SiteTree` objects, but now
all `DataObject` classes.
 - `SiteTreeLinkTracking` -> Tracks links between any object and SiteTree objects,
   generated from [sitetree_link] shortcodes in html areas.
 - `FileLinkTracking` -> Tracks links between any object and File objects, generated
  from [image] and [file_link] shortcodes in html areas.

Note that the `ImageTracking` property has been deprecated in favour of `FileTracking`,
which includes and tracks non-image files as well.

By default `HasBrokenFile` and `HasBrokenLink` properties are still supported, but
only for `SiteTree` objects by default. Non-SiteTree objects will still have
both `FileTracking` and `LinkTracking` relations available for tracking
linked records.

In addition, `File::BackLinkTracking()` and `SiteTree::BackLinkTracking()` are now polymorphic,
and may now both contain non-SiteTree objects. Polymorphic many_many through relations are
currently experimentally supported.

User code which relies on SiteTree-only results for these properties will need to be updated
to consider other types.

Additionally, the `SiteTree_LinkTracking` and `SiteTree_ImageTracking` tables no longer exist,
and are replaced by the `SiteTreeLink` and `FileLink` many_many through joining classes instead.
Code which relies on raw SQL queries to these tables will need to be updated.

`SiteTreeFileExtension` is deprecated, and has it's functionality baked directly into `File` dataobject.

### New upgrader command
The SilverStripe upgrader tool can now be used to convert your `_ss_environment.php` file to an equivalent `.env` file when migrating a SilverStripe 3 project to SilverStripe 4.

```
cd ~/my-project-root
upgrade-code environment --write
```