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 commands

Two new commands have been added to the SilverStripe upgrader tool: `environment` and `reorganise`.

`environment` allows you to convert your `_ss_environment.php` file to an equivalent `.env` file when migrating a SilverStripe 3 project to SilverStripe 4.

`reorganise` renames your `mysite` and `mysite/code` folders to `app` and `app/src`. It also warns you of any occurence of `mysite` in your codebase.

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

### New GridField Action Menu

A new `GridField_ActionMenu` is included by default in GridFields configured with `GridFieldConfig_RecordEditor`
or `GridFieldConfig_RelationEditor`.
In addition to this `GridFieldDeleteAction` and `GridFieldEditButton` now implement `GridField_ActionMenuItem`,
this means that any GridField that uses a config of or based on `GridFieldConfig_RecordEditor` 
or `GridFieldConfig_RelationEditor` will have an action menu on each item row with
the 'Delete/Unlink' and 'Edit' actions moved into it.

If you wish to opt out of having this menu and the respective actions moved into it, you can remove the `GridField_ActionMenu`
component from the config that is passed into your GridField.

```php
// method 1: removing GridField_ActionMenu from a new GridField
$config = GridFieldConfig_RecordEditor::create();
$config->removeComponentsByType(GridField_ActionMenu);

$gridField = new GridField('Teams', 'Teams', $this->Teams(), $config);

// method 2: removing GridField_ActionMenu from an existing GridField
$gridField->getConfig()->removeComponentsByType(GridField_ActionMenu);
```
### Versioned cache segmentation

`SilverStripe\Core\Cache\CacheFactory` now maintains separate cache pools for each versioned stage. This prevents developers from caching draft data and then accidentally exposing it on the live stage without potentially required authorisation checks. Unless you rely on caching across stages, you don't need to change your own code for this change to take effect. Note that cache keys will be internally rewritten, causing any existing cache items to become invalid when this change is deployed.

```php
// Before:
$cache = Injector::inst()->get(CacheInterface::class . '.myapp');
Versioned::set_stage(Versioned::DRAFT);
$cache->set('my_key', 'Some draft content. Not for public viewing yet.');
Versioned::set_stage(Versioned::LIVE);
$cache->get('my_key'); // 'Some draft content. Not for public viewing yet'

// After:
$cache = Injector::inst()->get(CacheInterface::class . '.myapp');
Versioned::set_stage(Versioned::DRAFT);
$cache->set('my_key', 'Some draft content. Not for public viewing yet.');
Versioned::set_stage(Versioned::LIVE);
$cache->get('my_key'); // null
```
Data that is not content sensitive can be cached across stages by simply opting out of the segmented cache with the `disable-container` argument.

```yaml
SilverStripe\Core\Injector\Injector:
  Psr\SimpleCache\CacheInterface.myapp:
    factory: SilverStripe\Core\Cache\CacheFactory     
    constructor:
      namespace: "MyInsensitiveData"
      args:
        disable-container: true 
``` 

### HTTP Cache Header changes

#### Overview

In order to support developers in making safe choices around HTTP caching,
we've introduced a `HTTPCacheControlMiddleware` class to control if a response
should be considered public or private. This is an abstraction on existing
lowlevel APIs like `HTTP::add_cache_headers()` and `HTTPResponse->addHeader()`.

This change introduces smaller but necessary changes to HTTP caching headers
sent by SilverStripe. If you are relying on HTTP caching in your implementation,
or use modules such as [silverstripe/controllerpolicy](https://github.com/silverstripe/silverstripe-controllerpolicy),
please review the implications of these changes below. 

In short, these APIs make it easier to express your caching preferences
without running the risk of overriding essential core safety measures.
Most commonly, these APIs will prevent HTTP caching of draft content.

It will also prevent caching of content generated with an active session,
since the system can't tell whether session data was used to vary the output.
In this case, it's up to the developer to opt-in to caching,
after ensuring that certain execution paths are safe despite of using sessions.

The system behaviour does not guard against accidentally caching "private" content,
since there are too many variations under which output could be considered private
(e.g. a custom "approval" flag on a comment object). It is up to
the developer to ensure caching is used appropriately there.

By default, SilverStripe sends headers which signal to HTTP caches
that the response should be considered not cacheable.

See [Developer Guide: Performance > HTTP Cache Headers](/developer_guide/performance/http_cache_headers)
for details on the new API.

#### Disabling legacy cache headers

In order to forcibly disable all deprecated HTTP APIs you can set the below config:

```yaml
SilverStripe\Control\HTTP:
  ignoreDeprecatedCaching: true
```

This will ensure that any code paths that use the old API will not interefere with upgraded code
that interferes with the new behaviour.

#### Example Usage

##### Global opt-in for page content 

Enable caching for all page content (through `PageController`).

```diff
<?php

-use SilverStripe\Control\HTTP;
+use SilverStripe\Control\Middleware\HTTPCacheControlMiddleware;
use SilverStripe\CMS\Controllers\ContentController;

class PageController extends ContentController
{
    public function init()
    {
-        HTTP::set_cache_age(60);
+        HTTPCacheControlMiddleware::singleton()
+           ->enableCache()
+           ->setMaxAge(60); // 1 minute
        
        parent::init();
    }
}
```

Note: SilverStripe will still override this preference when a session is active,
a [CSRF token](/developer_guides/forms/form_security) token is present,
or draft content has been requested.

##### Opt-out for a particular controller action

If a controller output relies on session data, cookies,
permission checks or other triggers for conditional output,
you can disable caching either on a controller level
(through `init()`) or for a particular action.

```diff
<?php

-use SilverStripe\Control\HTTP;
+use SilverStripe\Control\Middleware\HTTPCacheControlMiddleware;
use SilverStripe\CMS\Controllers\ContentController;

class PageController extends ContentController
{
    public function myprivateaction($request)
    {
-        HTTP::set_cache_age(0);
+        HTTPCacheControlMiddleware::singleton()
+           ->disableCache();
        
        return $this->myPrivateResponse();
    }
}
```

Note: SilverStripe will still override this preference when a session is active,
a [CSRF token](/developer_guides/forms/form_security) token is present,
or draft content has been requested.

##### Global opt-in, ignoring session (advanced)

This can be helpful in situations where forms are embedded on the website.
SilverStripe will still override this preference when draft content has been requested.
CAUTION: This mode relies on a developer examining each execution path to ensure
that no session data is used to vary output. 

Use case: By default, forms include a [CSRF token](/developer_guides/forms/form_security)
which starts a session with a value that's unique to the visitor, which makes the output uncacheable.
But any subsequent requests by this visitor will also carry a session, leading to uncacheable output
for this visitor. This is the case even if the output does not contain any forms,
and does not vary for this particular visitor.

```diff
<?php

-use SilverStripe\Control\HTTP;
+use SilverStripe\Control\Middleware\HTTPCacheControlMiddleware;
use SilverStripe\CMS\Controllers\ContentController;

class PageController extends ContentController
{
    public function init()
    {
-        HTTP::set_cache_age(60);
+        HTTPCacheControlMiddleware::singleton()
+           ->enableCache($force=true) // DANGER ZONE
+           ->setMaxAge(60); // 1 minute

        parent::init();
    }
}
```

#### Detailed Cache-Control Changes:

 * Added `Cache-Control: no-store` header to default responses,
   to prevent intermediary HTTP proxies (e.g. CDNs) from caching unless developers opt-in
 * Removed `Cache-Control: no-transform` header from default responses
 * Removed `Vary: Cookie` as an unreliable cache buster,
   rely on the existing `Cache-Control: no-store` defaults instead
 * Removed `Vary: Accept`, since it's very uncommon to vary content on
   the `Accept` headers submitted through the request,
   and it can significantly decrease the likelyhood of a cache hit.
   Note this is different from `Vary: Accept-Encoding`,
   which is important for compression (e.g. gzip), and usually added by
   other layers such as Apache's mod_gzip.