Delegate cancellation to promise

Author: mainej

src/lsp4clj/server.clj

@@ -31,7 +31,7 @@
 (defprotocol IBlockingDerefOrCancel
   (deref-or-cancel [this timeout-ms timeout-val]))
 
-(defrecord PendingRequest [p id method started server]
+(defrecord PendingRequest [p id method started]
   clojure.lang.IDeref
   (deref [_] (deref p))
   clojure.lang.IBlockingDeref
@@ -56,12 +56,8 @@
   (isCancelled [_] (p/cancelled? p))
   (isDone [_] (p/done? p))
   (cancel [_ _interrupt?]
-    (if (p/done? p)
-      false
-      (do
-        (p/cancel! p)
-        (protocols.endpoint/send-notification server "$/cancelRequest" {:id id})
-        true)))
+    (p/cancel! p)
+    (p/cancelled? p))
   p.protocols/IPromiseFactory
   (-promise [_] p))
 
@@ -91,11 +87,17 @@
   Sends `$/cancelRequest` only once, though `lsp4clj.server/deref-or-cancel` or
   `future-cancel` can be called multiple times."
   [id method started server]
-  (map->PendingRequest {:p (p/deferred)
-                        :id id
-                        :method method
-                        :started started
-                        :server server}))
+  ;; Chaining `(-> (p/deferred) (p/catch ...))` seems like it should work, but
+  ;; doesn't.
+  (let [p (p/deferred)]
+    (p/catch p CancellationException
+      (fn [ex]
+        (protocols.endpoint/send-notification server "$/cancelRequest" {:id id})
+        (p/rejected ex)))
+    (map->PendingRequest {:p p
+                          :id id
+                          :method method
+                          :started started})))
 
 (defn ^:private format-error-code [description error-code]
   (let [{:keys [code message]} (lsp.errors/by-key error-code)]

test/lsp4clj/server_test.clj

@@ -290,7 +290,7 @@
     (h/assert-take output-ch)
     (is (future-cancel req))
     (is (= "$/cancelRequest" (:method (h/assert-take output-ch))))
-    (is (not (future-cancel req)))
+    (is (future-cancel req))
     (h/assert-no-take output-ch)
     (server/shutdown server)))
 
@@ -402,9 +402,12 @@
                                       :input-ch input-ch})
           _ (server/start server nil)
           req (p/promise (server/send-request server "req" {:body "foo"}))]
+      (h/assert-take output-ch)
       (p/cancel! req)
       (is (p/done? req))
       (is (p/cancelled? req))
+      (is (= {:jsonrpc "2.0", :method "$/cancelRequest", :params {:id 1}}
+             (h/assert-take output-ch)))
       (server/shutdown server))))
 
 (def fixed-clock