1 files changed, 70 insertions, 0 deletions
diff --git a/doc/disfluid.texi b/doc/disfluid.texi
index fa5347a..6b9ad08 100644
--- a/doc/disfluid.texi
+++ b/doc/disfluid.texi
@@ -1539,10 +1539,80 @@ Return the path prefix @var{endpoint} is configured to respond to.
 Check if @var{endpoint} is configured to respond to @var{request}.
 @end deffn
 
+The handler may throw exceptions to signal errors. Exception messages
+will be printed to the log file, and user messages will be passed to
+the user.
+
 @menu
+* Error signalling::
 * Router endpoint::
 @end menu
 
+@node Error signalling
+@section Error signalling
+The @emph{(webid-oidc server endpoint)} module defines exception types
+that can be emitted to abort the computation in a handler. If an
+exception of a different kind is raised, this will lead to a 500
+Internal Server Error response.
+
+@deftp {Exception type} &web-exception @var{code} @var{reason-phrase}
+The request failed, with @var{code} and @var{reason-phrase}.
+@end deftp
+
+@deffn {function} make-web-exception @var{code} @var{reason-phrase}
+Create an exception with @var{code} and @var{reason-phrase}.
+@end deffn
+
+@deffn {function} web-exception? @var{exn}
+Check if @var{exn} was thrown because the request failed.
+@end deffn
+
+@deffn {function} web-exception-code @var{exn}
+@deffnx {function} web-exception-reason-phrase @var{exn}
+Return the code and reason-phrase for when @var{exn} was thrown, if it
+was thrown because of a failing request.
+@end deffn
+
+@deftp {Exception type} &caused-by-user @var{webid}
+If a web exception is raised, maybe it is caused by some user
+identified by @var{webid} (an URI, or @code{#f}.
+@end deftp
+
+@deffn {function} make-caused-by-user @var{webid}
+Constructor for @code{&caused-by-user}.
+@end deffn
+
+@deffn {function} caused-by-user? @var{exn}
+Check if @var{exn} was caused by the user.
+@end deffn
+
+@deffn {function} caused-by-user-webid @var{exn}
+Return the webid of the user that caused @var{exn}.
+@end deffn
+
+@deftp {Exception type} &user-message @var{sxml}
+An exception containing a message that is safe to show to the user, as
+an SXML fragment of XHTML. Typically, this would be a @code{<p/>}, or
+a @code{<div/>}.
+
+You can set a user-message multiple times. The occurences will be
+concatenated in the response, in the order they appear in the
+composite exception.
+@end deftp
+
+@deffn {function} make-user-message @var{sxml}
+Create a new user message containing the @var{sxml} fragment.
+@end deffn
+
+@deffn {function} user-message? @var{exn}
+Check if there is at least one user message in @var{exn}.
+@end deffn
+
+@deffn {function} user-message-sxml @var{exn}
+Return all user messages in @var{exn}, as a @code{<div/>} SXML
+fragment.
+@end deffn
+
 @node Router endpoint
 @section Router endpoint
 The first non-trivial handler is for the router endpoint, defined in