Add PUBLIC_COLLECTION constant for public addressing

CHANGES.md

@@ -8,6 +8,10 @@ Version 0.7.0
 
 To be released.
 
+ -  Added `PUBLIC_COLLECTION` constant for [public addressing].
+
+[public addressing]: https://www.w3.org/TR/activitypub/#public-addressing
+
 
 Version 0.6.0
 -------------

docs/manual/send.md

@@ -132,7 +132,7 @@ recipient's personal inbox.  To deliver an activity to the shared inbox,
 you can pass the `preferSharedInbox` option:
 
 ~~~~ typescript
-import { Actor, Context, Create, Note } from "@fedify/fedify";
+import { Actor, Context, Create, Note, PUBLIC_COLLECTION } from "@fedify/fedify";
 
 async function sendNote(
   ctx: Context<void>,
@@ -144,10 +144,10 @@ async function sendNote(
     recipient,
     new Create({
       actor: ctx.getActorUri(senderHandle),
-      to: new URL("https://www.w3.org/ns/activitystreams#Public"),
+      to: PUBLIC_COLLECTION,
       object: new Note({
         attribution: ctx.getActorUri(senderHandle),
-        to: new URL("https://www.w3.org/ns/activitystreams#Public"),
+        to: PUBLIC_COLLECTION,
       }),
     }),
     { preferSharedInbox: true },  // [!code highlight]
@@ -156,9 +156,12 @@ async function sendNote(
 ~~~~
 
 > [!TIP]
-> <https://www.w3.org/ns/activitystreams#Public> is a special IRI that
+> `PUBLIC_COLLECTION` constant contains a `URL` object of
+> <https://www.w3.org/ns/activitystreams#Public>, a special IRI that
 > represents the public audience.  By setting the `to` property to this IRI,
-> the activity is visible to everyone.
+> the activity is visible to everyone.  See also the [*Public Addressing*
+> section](https://www.w3.org/TR/activitypub/#public-addressing) in the
+> ActivityPub specification.
 
 > [!NOTE]
 > To deliver an activity to the shared inbox, the recipient server must support

vocab/constants.ts

@@ -0,0 +1,11 @@
+/**
+ * The special public collection for [public addressing].  *Do not mutate this
+ * object.*
+ *
+ * [public addressing]: https://www.w3.org/TR/activitypub/#public-addressing
+ *
+ * @since 0.7.0
+ */
+export const PUBLIC_COLLECTION = new URL(
+  "https://www.w3.org/ns/activitystreams#Public",
+);

vocab/mod.ts

@@ -50,5 +50,6 @@
  * @module
  */
 export * from "./actor.ts";
+export * from "./constants.ts";
 export * from "./lookup.ts";
 export * from "./vocab.ts";