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Breaking update of the cowboy_req interface

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Simplify the interface for most cowboy_req functions. They all return
a single value except the four body reading functions. The reply functions
now only return a Req value.

Access functions do not return a Req anymore.

Functions that used to cache results do not have a cache anymore.

The interface for accessing query string and cookies has therefore
been changed.

There are now three query string functions: qs/1 provides access
to the raw query string value; parse_qs/1 returns the query string
as a list of key/values; match_qs/2 returns a map containing the
values requested in the second argument, after applying constraints
and default value.

Similarly, there are two cookie functions: parse_cookies/1 and
match_cookies/2. More match functions will be added in future commits.

None of the functions return an error tuple anymore. It either works
or crashes. Cowboy will attempt to provide an appropriate status code
in the response of crashed handlers.

As a result, the content decode function has its return value changed
to a simple binary, and the body reading functions only return on success.
This commit is contained in:
Loïc Hoguin 2014-09-23 16:43:29 +03:00
parent b57f94661f
commit f1c3b6d76f
61 changed files with 814 additions and 767 deletions
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41
doc/src/guide/cookies.ezdoc
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@ -116,22 +116,47 @@ As we said, the client sends cookies with every request.
But unlike the server, the client only sends the cookie
name and value.
You can read the value of a cookie.
Cowboy provides two different ways to read cookies. You
can either parse them as a list of key/value pairs, or
match them into a map, optionally applying constraints
to the values or providing a default if they are missing.
You can parse the cookies and then use standard library
functions to access individual values.
``` erlang
{CookieVal, Req2} = cowboy_req:cookie(<<"lang">>, Req).
Cookies = cowboy_req:parse_cookies(Req),
{_, Lang} = lists:keyfind(<<"lang">>, 1, Cookies).
```
You can also get a default value returned when the cookie
isn't set.
You can match the cookies into a map.
``` erlang
{CookieVal, Req2} = cowboy_req:cookie(<<"lang">>, Req, <<"fr">>).
#{id := ID, lang := Lang} = cowboy_req:match_cookies(Req, [id, lang]).
```
And you can obtain all cookies at once as a list of
key/value tuples.
You can use constraints to validate the values while matching
them. The following snippet will crash if the `id` cookie is
not an integer number or if the `lang` cookie is empty. Additionally
the `id` cookie value will be converted to an integer term, saving
you a conversion step.
``` erlang
{AllCookies, Req2} = cowboy_req:cookies(Req).
CookiesMap = cowboy_req:match_cookies(Req, [{id, int}, {lang, nonempty}]).
```
Note that if two cookies share the same name, then the map value
will be a list of the two cookie values.
Read more about ^constraints^.
A default value can be provided. The default will be used
if the `lang` cookie is not found. It will not be used if
the cookie is found but has an empty value.
``` erlang
#{lang := Lang} = cowboy_req:match_cookies(Req, [{lang, [], <<"en-US">>}]).
```
If no default is provided and the value is missing, the
query string is deemed invalid and the process will crash.