From 66bb5251e89487c5fb8c1f10b8ceb2c6c8f31eed Mon Sep 17 00:00:00 2001
From: Anders Svensson <anders@erlang.org>
Date: Thu, 13 Jul 2017 01:09:57 +0200
Subject: Add service_opt() strict_arities

To be able to disable the relatively expensive check that the number of
AVPs received in a message or grouped AVP agrees with the dictionary in
question. The may well be easier for the user in handle_request/answer
callbacks, when digesting the received message, and in some cases may
not be important.

The check at encode can also be disabled, allowing messages that don't
agree with the dictionary in question to be sent, which can be useful in
test (at least).
---
 lib/diameter/doc/src/diameter.xml | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

(limited to 'lib/diameter/doc')

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 43cb3a538c..017f6bb01d 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -955,6 +955,37 @@ Options <c>monitor</c> and <c>link</c> are ignored.</p>
 Defaults to the empty list.</p>
 </item>
 
+<tag>
+<marker id="strict_arities"/><c>{strict_arities, boolean()
+                                               | encode
+                                               | decode}</c></tag>
+<item>
+<p>
+Whether or not to require that the number of AVPs in a message or
+grouped AVP agree with those specified in the dictionary in question.
+If <c>true</c> then mismatches in an outgoing messages cause message
+encoding to fail, while mismatches in an incoming message are reported
+as 5005/5009 errors in the errors field of the diameter_packet record
+passed to &app_handle_request; or &app_handle_answer; callbacks.
+If <c>false</c> then neither error is enforced/detected.
+If <c>encode</c> or <c>decode</c> then errors are only
+enforced/detected on outgoing or incoming messages respectively.</p>
+
+<p>
+Defaults to <c>true</c>.</p>
+
+<note>
+<p>
+Disabling arity checks affects the form of messages at encode/decode.
+In particular, decoded AVPs are represented as lists of values,
+regardless of the AVP's arity (ie. expected number in the message/AVP
+grammar in question), and values are expected to be supplied as lists
+at encode.
+This differs from the historic decode behaviour of representing AVPs
+of arity 1 as bare values, not wrapped in a list.</p>
+</note>
+</item>
+
 <tag>
 <marker id="strict_mbit"/><c>{strict_mbit, boolean()}</c></tag>
 <item>
-- 
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