improving component inheritance

[amitu]

If we want to patch some existing component we have to copy over all its arguments.

-- import: doc-site

-- component page:
optional caption title:
children children:
optional body body:

-- doc-site.page: $page.title
children: $page.children
body: $page.body

-- doc-site.page.sidebar: 

-- ftd.text: Awesome Sidebar

-- end: doc-site.page.sidebar: 
-- end: doc-site.page

-- end: page

If the original component was further updated to add another argument, our patched component will have to be updated. This is tedious and error prone.

Imagine if we can write this:

-- import: doc-site

-- component page:
inherit: doc-site.page

-- inherited:

-- inherited.sidebar: 
-- ftd.text: Awesome Sidebar
-- end: inherited.sidebar: 

-- end: inherited

-- end: page

Notice how we instead of defining arguments we used inherit: doc-site.page. This copies over all the arguments from the inherited component. We can define more arguments if we want. And we can define default values for existing arguments as well. We can even change the type of argument if we wanted.

Notice then how we used -- inherited:. This will pass all the arguments we have that can be passed to inherited component. If we have defined extra argument and we want to pass them to original component we can do that as well.