Limit the size of data printed by the debugger

src/cider/nrepl/middleware/debug.clj

@@ -117,12 +117,22 @@
   "Bound by the `breakpoint` macro to the local &env."
   {})
 
+(def print-length (atom nil))
+(def print-level (atom nil))
+
+(defn pr-short
+  "Like `pr-str` but limited in length and depth."
+  [x]
+  (binding [*print-length* @print-length
+            *print-level*  @print-level]
+    (pr-str x)))
+
 (defn- locals-for-message
   "Prepare a map of local variables for sending through the repl.
   This involves removing any keys whose name looks like it was
   autogenerated by a macro, and turning keys and values to strings."
   [m]
-  (map (partial map pr-str)
+  (map (partial map pr-short)
        (remove (fn [[k]] (re-find  #"_" (name k))) m)))
 
 (defn- read-debug
@@ -215,7 +225,7 @@
                      (inspect-then-read-command value extras))
       :inject   (read-debug-eval-expression "Expression to inject: " extras code)
       :eval     (let [return (read-debug-eval-expression "Expression to evaluate: " extras code)]
-                  (read-debug-command value (assoc extras :debug-value (pr-str return))))
+                  (read-debug-command value (assoc extras :debug-value (pr-short return))))
       :quit     (abort!))))
 
 ;;; ## High-level functions
@@ -238,7 +248,7 @@
                 (assoc ~(let [{:keys [code id file point]} *msg*]
                           {:code code, :original-id id, :coor coor
                            :file file, :point point})
-                       :debug-value (pr-str val#)))))))
+                       :debug-value (pr-short val#)))))))
 
 ;;; Data readers
 (defn breakpoint-reader
@@ -294,11 +304,13 @@
 
 (defn- initialize
   "Initialize the channel used for debug-input requests."
-  [msg]
+  [{:keys [print-length print-level] :as msg}]
   (when-let [stored-message @debugger-message]
     (transport/send (:transport stored-message)
                     (response-for stored-message :status :done)))
   ;; The above is just bureaucracy. The below is important.
+  (reset! @#'print-length print-length)
+  (reset! @#'print-level print-level)
   (reset! debugger-message msg))
 
 (defn- instrumented-defs-reply

test/clj/cider/nrepl/middleware/debug_test.clj

@@ -169,3 +169,33 @@
     (is (:cider-breakfunction (meta (read-string "#dbg [a b c]"))))
     (is (= (count (remove #(:cider-breakfunction (meta %)) (read-string "#dbg [a :b 10]")))
            2))))
+
+(deftest pr-short
+  (reset! d/print-length 4)
+  (reset! d/print-level 2)
+  (is (< (count (d/pr-short [1 2 3 4 5 6 7 8 9 10]))
+         (count (pr-str [1 2 3 4 5 6 7 8 9 10]))))
+  (is (< (count (d/pr-short [[[1 2 3 4]]]))
+         (count (pr-str [[[1 2 3 4]]]))))
+  (is (= (d/pr-short [1 2 3 4])
+         (pr-str [1 2 3 4]))))
+
+(deftest breakpoint
+  ;; Map merging
+  (with-redefs [d/read-debug-command (fn [v e] (assoc e :value v))
+                d/debugger-message (atom [:fake])]
+    (binding [*msg* {:session (atom {#'d/*skip-breaks* false})
+                     :code :code, :id :id, :file :file, :point :point}]
+      (let [m (eval '(cider.nrepl.middleware.debug/breakpoint (inc 10) [6]))]
+        (are [k v] (= (k m) v)
+          :value 11
+          :debug-value "11"
+          :coor [6]
+          :file :file
+          :point :point
+          :code :code
+          :original-id :id))
+      ;; Locals capturing
+      (reset! @#'d/debugger-message nil)
+      (is (= (eval '(let [x 10] (cider.nrepl.middleware.debug/breakpoint cider.nrepl.middleware.debug/*locals* [])))
+             '{x 10})))))