/
router.ex
526 lines (399 loc) · 15.9 KB
/
router.ex
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
defmodule Plug.Router do
@moduledoc ~S"""
A DSL to define a routing algorithm that works with Plug.
It provides a set of macros to generate routes. For example:
defmodule AppRouter do
use Plug.Router
plug :match
plug :dispatch
get "/hello" do
send_resp(conn, 200, "world")
end
match _ do
send_resp(conn, 404, "oops")
end
end
Each route needs to return a connection, as per the Plug spec.
A catch-all `match` is recommended to be defined as in the example
above, otherwise routing fails with a function clause error.
The router is itself a plug, which means it can be invoked as:
AppRouter.call(conn, AppRouter.init([]))
Notice the router contains a plug pipeline and by default it requires
two plugs: `match` and `dispatch`. `match` is responsible for
finding a matching route which is then forwarded to `dispatch`.
This means users can easily hook into the router mechanism and add
behaviour before match, before dispatch or after both.
To specify private options on `match` that can be used by plugs
before `dispatch` pass an option with key `:private` containing a map.
Example:
get "/hello", private: %{an_option: :a_value} do
send_resp(conn, 200, "world")
end
These options are assigned to `:private` in the call's `Plug.Conn`.
## Routes
get "/hello" do
send_resp(conn, 200, "world")
end
In the example above, a request will only match if it is a `GET` request and
the route is "/hello". The supported HTTP methods are `get`, `post`, `put`,
`patch`, `delete` and `options`.
A route can also specify parameters which will then be
available in the function body:
get "/hello/:name" do
send_resp(conn, 200, "hello #{name}")
end
The `:name` parameter will also be available in the function body as
`conn.params["name"]` and `conn.path_params["name"]`.
Routes allow for globbing which will match the remaining parts
of a route and can be available as a parameter in the function
body. Also note that a glob can't be followed by other segments:
get "/hello/*_rest" do
send_resp(conn, 200, "matches all routes starting with /hello")
end
get "/hello/*glob" do
send_resp(conn, 200, "route after /hello: #{inspect glob}")
end
Finally, a general `match` function is also supported:
match "/hello" do
send_resp(conn, 200, "world")
end
A `match` will match any route regardless of the HTTP method.
Check `match/3` for more information on how route compilation
works and a list of supported options.
## Parameter Parsing
Handling request data can be done through the
[`Plug.Parsers`](https://hexdocs.pm/plug/Plug.Parsers.html#content) plug. It
provides support for parsing URL-encoded, form-data, and JSON data as well as
providing a behaviour that others parsers can adopt.
Here is an example of `Plug.Parsers` can be used in a `Plug.Router` router to
parse the JSON-encoded body of a POST request:
defmodule AppRouter do
use Plug.Router
plug :match
plug Plug.Parsers, parsers: [:json],
pass: ["application/json"],
json_decoder: Jason
plug :dispatch
post "/hello" do
IO.inspect conn.body_params # Prints JSON POST body
send_resp(conn, 200, "Success!")
end
end
It is important that `Plug.Parsers` is placed before the `:dispatch` plug in
the pipeline, otherwise the matched clause route will not receive the parsed
body in its `Plug.Conn` argument when dispatched.
`Plug.Parsers` can also be plugged between `:match` and `:dispatch` (like in
the example above): this means that `Plug.Parsers` will run only if there is a
matching route. This can be useful to perform actions such as authentication
*before* parsing the body, which should only be parsed if a route matches
afterwards.
## Error handling
In case something goes wrong in a request, the router by default
will crash, without returning any response to the client. This
behaviour can be configured in two ways, by using two different
modules:
* `Plug.ErrorHandler` - allows the developer to customize exactly
which page is sent to the client via the `handle_errors/2` function;
* `Plug.Debugger` - automatically shows debugging and request information
about the failure. This module is recommended to be used only in a
development environment.
Here is an example of how both modules could be used in an application:
defmodule AppRouter do
use Plug.Router
if Mix.env == :dev do
use Plug.Debugger
end
use Plug.ErrorHandler
plug :match
plug :dispatch
get "/hello" do
send_resp(conn, 200, "world")
end
defp handle_errors(conn, %{kind: _kind, reason: _reason, stack: _stack}) do
send_resp(conn, conn.status, "Something went wrong")
end
end
## Routes compilation
All routes are compiled to a match function that receives
three arguments: the method, the request path split on `/`
and the connection. Consider this example:
match "/foo/bar", via: :get do
send_resp(conn, 200, "hello world")
end
It is compiled to:
defp match("GET", ["foo", "bar"], conn) do
send_resp(conn, 200, "hello world")
end
This means guards can be given to `match`:
match "/foo/bar/:baz" when size(baz) <= 3, via: :get do
send_resp(conn, 200, "hello world")
end
After a match is found, the block given as `do/end` is stored
as a function in the connection. This function is then retrieved
and invoked in the `dispatch` plug.
## Options
When used, the following options are accepted by `Plug.Router`:
* `:log_on_halt` - accepts the level to log whenever the request is halted
"""
@doc false
defmacro __using__(opts) do
quote location: :keep do
import Plug.Router
@before_compile Plug.Router
use Plug.Builder, unquote(opts)
@doc false
def match(conn, _opts) do
do_match(conn, conn.method, Enum.map(conn.path_info, &URI.decode/1), conn.host)
end
@doc false
def dispatch(%Plug.Conn{assigns: assigns} = conn, _opts) do
{_path, fun} = Map.fetch!(conn.private, :plug_route)
fun.(conn)
end
defoverridable match: 2, dispatch: 2
end
end
@doc false
defmacro __before_compile__(env) do
unless Module.defines?(env.module, {:do_match, 4}) do
raise "no routes defined in module #{inspect(env.module)} using Plug.Router"
end
quote do
import Plug.Router, only: []
end
end
@doc """
Returns the path of the route that the request was matched to.
"""
@spec match_path(Plug.Conn.t()) :: String.t()
def match_path(%Plug.Conn{} = conn) do
{path, _fun} = Map.fetch!(conn.private, :plug_route)
path
end
## Match
@doc """
Main API to define routes.
It accepts an expression representing the path and many options
allowing the match to be configured.
The route can dispatch either to a function body or a Plug module.
## Examples
match "/foo/bar", via: :get do
send_resp(conn, 200, "hello world")
end
match "/baz", to: MyPlug, init_opts: [an_option: :a_value]
## Options
`match/3` and the other route macros accept the following options:
* `:host` - the host which the route should match. Defaults to `nil`,
meaning no host match, but can be a string like "example.com" or a
string ending with ".", like "subdomain." for a subdomain match.
* `:private` - assigns values to `conn.private` for use in the match
* `:assigns` - assigns values to `conn.assigns` for use in the match
* `:via` - matches the route against some specific HTTP method (specified as
an atom, like `:get` or `:put`.
* `:do` - contains the implementation to be invoked in case
the route matches.
* `:to` - a Plug that will be called in case the route matches.
* `:init_opts` - the options for the target Plug given by `:to`.
A route should specify only one of `:do` or `:to` options.
"""
defmacro match(path, options, contents \\ []) do
compile(nil, path, options, contents)
end
@doc """
Dispatches to the path only if the request is a GET request.
See `match/3` for more examples.
"""
defmacro get(path, options, contents \\ []) do
compile(:get, path, options, contents)
end
@doc """
Dispatches to the path only if the request is a POST request.
See `match/3` for more examples.
"""
defmacro post(path, options, contents \\ []) do
compile(:post, path, options, contents)
end
@doc """
Dispatches to the path only if the request is a PUT request.
See `match/3` for more examples.
"""
defmacro put(path, options, contents \\ []) do
compile(:put, path, options, contents)
end
@doc """
Dispatches to the path only if the request is a PATCH request.
See `match/3` for more examples.
"""
defmacro patch(path, options, contents \\ []) do
compile(:patch, path, options, contents)
end
@doc """
Dispatches to the path only if the request is a DELETE request.
See `match/3` for more examples.
"""
defmacro delete(path, options, contents \\ []) do
compile(:delete, path, options, contents)
end
@doc """
Dispatches to the path only if the request is an OPTIONS request.
See `match/3` for more examples.
"""
defmacro options(path, options, contents \\ []) do
compile(:options, path, options, contents)
end
@doc """
Forwards requests to another Plug. The `path_info` of the forwarded
connection will exclude the portion of the path specified in the
call to `forward`. If the path contains any parameters, those will
be available in the target Plug in `conn.params` and `conn.path_params`.
## Options
`forward` accepts the following options:
* `:to` - a Plug the requests will be forwarded to.
* `:init_opts` - the options for the target Plug.
* `:host` - a string representing the host or subdomain, exactly like in
`match/3`.
* `:private` - values for `conn.private`, exactly like in `match/3`.
* `:assigns` - values for `conn.assigns`, exactly like in `match/3`.
If `:init_opts` is undefined, then all remaining options are passed
to the target plug.
## Examples
forward "/users", to: UserRouter
Assuming the above code, a request to `/users/sign_in` will be forwarded to
the `UserRouter` plug, which will receive what it will see as a request to
`/sign_in`.
forward "/foo/:bar/qux", to: FooPlug
Here, a request to `/foo/BAZ/qux` will be forwarded to the `FooPlug`
plug, which will receive what it will see as a request to `/`,
and `conn.params["bar"]` will be set to `"BAZ"`.
Some other examples:
forward "/foo/bar", to: :foo_bar_plug, host: "foobar."
forward "/baz", to: BazPlug, init_opts: [plug_specific_option: true]
"""
defmacro forward(path, options) when is_binary(path) do
quote bind_quoted: [path: path, options: options] do
{target, options} = Keyword.pop(options, :to)
{options, plug_options} = Keyword.split(options, [:host, :private, :assigns])
plug_options = Keyword.get(plug_options, :init_opts, plug_options)
if is_nil(target) or !is_atom(target) do
raise ArgumentError, message: "expected :to to be an alias or an atom"
end
{target, target_opts} =
case Atom.to_string(target) do
"Elixir." <> _ -> {target, target.init(plug_options)}
_ -> {{__MODULE__, target}, plug_options}
end
@plug_forward_target target
@plug_forward_opts target_opts
# Delegate the matching to the match/3 macro along with the options
# specified by Keyword.split/2.
match path <> "/*glob", options do
Plug.Router.Utils.forward(
var!(conn),
var!(glob),
@plug_forward_target,
@plug_forward_opts
)
end
end
end
## Match Helpers
@doc false
def __route__(method, path, guards, options) do
{method, guards} = build_methods(List.wrap(method || options[:via]), guards)
{vars, match} = Plug.Router.Utils.build_path_match(path)
params_match = Plug.Router.Utils.build_path_params_match(vars)
private = extract_merger(options, :private)
assigns = extract_merger(options, :assigns)
host_match = Plug.Router.Utils.build_host_match(options[:host])
{quote(do: conn), method, match, params_match, host_match, guards, private, assigns}
end
@doc false
def __put_route__(conn, path, fun) do
Plug.Conn.put_private(conn, :plug_route, {append_match_path(conn, path), fun})
end
defp append_match_path(%Plug.Conn{private: %{plug_route: {base_path, _}}}, path) do
base_path <> path
end
defp append_match_path(%Plug.Conn{}, path) do
path
end
# Entry point for both forward and match that is actually
# responsible to compile the route.
defp compile(method, expr, options, contents) do
{body, options} =
cond do
Keyword.has_key?(contents, :do) ->
{contents[:do], options}
Keyword.has_key?(options, :do) ->
Keyword.pop(options, :do)
options[:to] ->
{to, options} = Keyword.pop(options, :to)
{init_opts, options} = Keyword.pop(options, :init_opts, [])
body =
quote do
@plug_router_to.call(var!(conn), @plug_router_init)
end
options =
quote do
to = unquote(to)
@plug_router_to to
@plug_router_init to.init(unquote(init_opts))
unquote(options)
end
{body, options}
true ->
raise ArgumentError, message: "expected one of :to or :do to be given as option"
end
{path, guards} = extract_path_and_guards(expr)
quote bind_quoted: [
method: method,
path: path,
options: options,
guards: Macro.escape(guards, unquote: true),
body: Macro.escape(body, unquote: true)
] do
route = Plug.Router.__route__(method, path, guards, options)
{conn, method, match, params, host, guards, private, assigns} = route
defp do_match(unquote(conn), unquote(method), unquote(match), unquote(host))
when unquote(guards) do
unquote(private)
unquote(assigns)
merge_params = fn
%Plug.Conn.Unfetched{} -> unquote({:%{}, [], params})
fetched -> Map.merge(fetched, unquote({:%{}, [], params}))
end
conn = update_in(unquote(conn).params, merge_params)
conn = update_in(conn.path_params, merge_params)
Plug.Router.__put_route__(conn, unquote(path), fn var!(conn) -> unquote(body) end)
end
end
end
defp extract_merger(options, key) when is_list(options) do
if option = Keyword.get(options, key) do
quote do
conn = update_in(conn.unquote(key), &Map.merge(&1, unquote(Macro.escape(option))))
end
end
end
# Convert the verbs given with `:via` into a variable and guard set that can
# be added to the dispatch clause.
defp build_methods([], guards) do
{quote(do: _), guards}
end
defp build_methods([method], guards) do
{Plug.Router.Utils.normalize_method(method), guards}
end
defp build_methods(methods, guards) do
methods = Enum.map(methods, &Plug.Router.Utils.normalize_method(&1))
var = quote do: method
guards = join_guards(quote(do: unquote(var) in unquote(methods)), guards)
{var, guards}
end
defp join_guards(fst, true), do: fst
defp join_guards(fst, snd), do: quote(do: unquote(fst) and unquote(snd))
# Extract the path and guards from the path.
defp extract_path_and_guards({:when, _, [path, guards]}), do: {extract_path(path), guards}
defp extract_path_and_guards(path), do: {extract_path(path), true}
defp extract_path({:_, _, var}) when is_atom(var), do: "/*_path"
defp extract_path(path), do: path
end