ENH Add permission methods based on owner

[GuySartorelli]

Note

The behaviour of the link field itself is out of scope - see #103

Issue

• Permisson model #12

[sabina-talipova]

Could you provide an example of how I could test these changes, it seems to me that I am testing it incorrectly.
Steps I took for testing:

• I have a Page
• The page has all can* methods that return true.
• I have an ExternalLinkExtension which has a canView which returns false.
• When I create a new link, no matter what type, I do not see the new link in the LinkField.
• If I change the return value of ExternalLinkExtension::canView to true then everything works.

[GuySartorelli]

• I have a Page
• The page has all can* methods that return true.
• I have an ExternalLinkExtension which has a canView which returns false.
• When I create a new link, no matter what type, I do not see the new link in the LinkField.
• If I change the return value of ExternalLinkExtension::canView to true then everything works.

Seeing the permissions be respected in the LinkField is out of scope - you should call the can* method directly and check the returned value is what you think it should be.
But in this case, what you're seeing is the expected behaviour.

Here's what should happen, in a variety of scenarios:

If there are no extensions and no Owner

• canView(), canEdit(), and canDelete() should use the default value as defined in DataObject
• canCreate() should return true

If there are no extensions but there is an Owner

• canView() should return the same as $this->Owner()->canView()
• canEdit() and canDelete() should return the same as $this->Owner()->canEdit()
• canCreate() should return true

If there are extensions

Regardless of the value on the owner, or even if there is an owner or not, if the extension's can* method returns true or false, that value will be returned.

If the extension's can* method returns null, it is as though the extension isn't there, so use the appropriate heading above for whether there is an owner or not.

[sabina-talipova]

LGTM. Test locally.