Yesod.Core.Handler.languages checks first for a language set in the
user's session, prepending that value to YesodRequest{reqLangs}, so it
is respected above all else if present.
For context, reqLangs itself also includes the session, but just later
in line:
langs' = catMaybes [ lookup langKey gets -- Query _LANG
, lookup langKey cookies -- Cookie _LANG
, lookupText langKey session -- Session _LANG
] ++ langs -- Accept-Language(s)
In #1720, it was raised that allowing the session (something implicitly
present for any request) to override a query parameter (something
explicitly given on that request) is surprising.
We decided (without knowing what order reqLangs was doing) that query,
cookie, session, accept was best and languages should be changed to do
that. Conveniently, this just makes languages equivalent to reqLangs, so
that is what this patch does.
GHC 8.0 and later come with the `DeriveLift` extension for deriving
instances of `Language.Haskell.TH.Syntax.Lift`. `yesod-core` supports
GHC 8.2 and up, so it is able to make use of this. Not only does
`DeriveLift` make for much shorter code, but it also fixes warnings
that you get when compiling `yesod-core` with GHC 8.10 or later:
```
[20 of 31] Compiling Yesod.Routes.TH.Types ( src/Yesod/Routes/TH/Types.hs, interpreted )
src/Yesod/Routes/TH/Types.hs:34:10: warning: [-Wmissing-methods]
• No explicit implementation for
‘liftTyped’
• In the instance declaration for ‘Lift (ResourceTree t)’
|
34 | instance Lift t => Lift (ResourceTree t) where
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
src/Yesod/Routes/TH/Types.hs:49:10: warning: [-Wmissing-methods]
• No explicit implementation for
‘liftTyped’
• In the instance declaration for ‘Lift (Resource t)’
|
49 | instance Lift t => Lift (Resource t) where
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
src/Yesod/Routes/TH/Types.hs:59:10: warning: [-Wmissing-methods]
• No explicit implementation for
‘liftTyped’
• In the instance declaration for ‘Lift (Piece t)’
|
59 | instance Lift t => Lift (Piece t) where
| ^^^^^^^^^^^^^^^^^^^^^^^^
src/Yesod/Routes/TH/Types.hs:78:10: warning: [-Wmissing-methods]
• No explicit implementation for
‘liftTyped’
• In the instance declaration for ‘Lift (Dispatch t)’
|
78 | instance Lift t => Lift (Dispatch t) where
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
This is because `DeriveLift` fills in implementations of `liftTyped`,
a method that was introduced to `Lift` in `template-haskell-2.16.0.0`
(bundled with GHC 8.10).
* Add functions for setting description and OG meta
It's common that a website author will want to add a specific
description and Open Graph image to a given page in their website. These
functions are simple conveniences to add these meta tags to the document
head.
I decided against simply adding all possible meta tags, because not all
of them are useful, and even in the case of Open Graph tags, many of
them should be set only once and they should use the same value for the
entire website. In those cases, it's probably better for the website
author to add those tags in their layout template.
Closes https://github.com/yesodweb/yesod/issues/1659
