Everything compiles, tests pass.

src/dog_and_duck/quack/fault_messages.clj

@@ -23,6 +23,9 @@
    :no-context "Section 3 of the ActivityPub specification states Implementers SHOULD include the ActivityPub context in their object definitions`."
    :no-id-persistent "Persistent objects MUST have unique global identifiers."
    :no-id-transient "The ActivityPub specification allows objects without `id` fields only if they are intentionally transient; even so it is preferred that the object should have an explicit null id."
-   :null-id-persistent "Persistent objects MUST have non-null identifiers."
+   :no-inbox "Actor objects MUST have an `inbox` property, whose value MUST be a reference to an ordered collection."
+   :no-outbox "Actor objects MUST have an `outbox` property, whose value MUST be a reference to an ordered collection."
    :no-type "The ActivityPub specification states that the `type` field is optional, but it is hard to process objects with no known type."
+   :not-actor-type "The `type` value of the object was not a recognised actor type."
+   :null-id-persistent "Persistent objects MUST have non-null identifiers."
    :not-an-object "ActivityStreams object must be JSON objects."})

src/dog_and_duck/quack/picky.clj

@@ -207,9 +207,8 @@
 (defmacro nil-if-empty
   "if `x` is an empty collection, return `nil`; else return `x`."
   [x]
-  `(if (coll? ~x)
-     (nil-if-empty ~x)
-     ~x))
+  `(if (and (coll? ~x) (empty? ~x)) nil
+       ~x))
 
 (defn has-type-or-fault
   "If object `x` has a `:type` value which is `acceptable`, return `nil`;
@@ -271,7 +270,9 @@
    (uri-or-fault u severity if-missing-token if-missing-token))
   ([u severity if-missing-token if-invalid-token]
    (try
-     (uri? (URI. u))
+     (if (uri? (URI. u))
+       nil
+       (make-fault-object severity if-invalid-token))
      (catch URISyntaxException _
        (make-fault-object severity if-invalid-token))
      (catch NullPointerException _
@@ -306,10 +307,10 @@
     "Person"
     "Service"})
 
-(defmacro actor-type?
+(defn actor-type?
   "Return `true` if the `x` is a recognised actor type, else `false`."
   [^String x]
-  `(if (actor-types ~x) true false))
+  (if (actor-types x) true false))
 
 (defn has-actor-type?
   "Return `true` if the object `x` has a type which is an actor type, else 
@@ -344,11 +345,11 @@
     "Offer" "Question" "Reject" "Read" "Remove" "TentativeAccept"
     "TentativeReject" "Travel" "Undo" "Update" "View"})
 
-(defmacro verb-type?
+(defn verb-type?
   "`true` if `x`, a string, represents a recognised ActivityStreams activity
    type."
   [^String x]
-  `(if (verb-types ~x) true false))
+  (if (verb-types x) true false))
 
 (defn has-activity-type?
   "Return `true` if the object `x` has a type which is an activity type, else 
@@ -474,8 +475,8 @@
          :object
          (fn [v]
            (object-reference-or-faults v #{"Invite" "Person"}
-                                      :must
-                                      :bad-accept-target))))
+                                       :must
+                                       :bad-accept-target))))
 
 (def ^:const activity-required-properties
   "Properties activities should have, keyed by activity type. Values are maps 

src/dog_and_duck/quack/quack.clj

@@ -15,7 +15,9 @@
 
   (:require [dog-and-duck.quack.picky :refer [*reject-severity* activity-faults
                                               actor-faults filter-severity link-faults
-                                              object-faults persistent-object-faults]]))
+                                              object-faults persistent-object-faults]])
+
+  (:import [java.net URI URISyntaxException]))
 
 ;;;     Copyright (C) Simon Brooke, 2022
 
@@ -81,13 +83,16 @@
    *must be* to an actor object, but before, may only be to a URI pointing to 
    one."
   [x]
-  (and
-   (cond (string? x) (uri? (URI. x))
-         :else (actor? x))
-   true))
+  (try
+    (and
+     (cond (string? x) (uri? (URI. x))
+           :else (actor? x))
+     true)
+    (catch URISyntaxException _ false)
+    (catch NullPointerException _ false)))
 
 (defn activity?
-  "`true` iff `x` quacks like an activity, else false." 
+  "`true` iff `x` quacks like an activity, else false."
   ([x] (activity? x *reject-severity*))
   ([x severity]
    (empty? (filter-severity (activity-faults x) severity))))