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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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51
doc/src/guide/constraints.ezdoc Normal file
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::: Constraints
Cowboy provides an optional constraints based validation feature
when interacting with user input.
Constraints are first used during routing. The router uses
constraints to more accurately match bound values, allowing
to create routes where a segment is an integer for example,
and rejecting the others.
Constraints are also used when performing a match operation
on input data, like the query string or cookies. There, a
default value can also be provided for optional values.
Finally, constraints can be used to not only validate input,
but also convert said input into proper Erlang terms, all in
one step.
:: Structure
Constraints are provided as a list of fields and for each
field a list of constraints for that field can be provided.
Fields are either the name of the field; the name and
one or more constraints; or the name, one or more constraints
and a default value.
When no default value is provided then the field is required.
Otherwise the default value is used.
All constraints for a field will be used to match its value
in the order they are given. If the value is modified by a
constraint, the next constraint receives the updated value.
:: Built-in constraints
|| Constraint Description
|
| int Convert binary value to integer
| nonempty Ensures the binary value is non-empty
:: Custom constraint
In addition to the predefined constraints, Cowboy will accept
a fun. This fun must accept one argument and return one of
`true`, `{true, NewValue}` or `false`. The result indicates
whether the value matches the constraint, and if it does it
can optionally be modified. This allows converting the value
to a more appropriate Erlang term.
Note that constraint functions SHOULD be pure and MUST NOT crash.