Evaluate Clojure code in the running app (written by Claude)

eval-app.bb

#!/usr/bin/env bb

;; =============================================================================
;; eval-app - Evaluate Clojure code in the running app
;; =============================================================================
;;
;; This tool connects to the nREPL of the app running evaluates Clojure code. 
;; Useful for inspecting app state, querying the database, or debugging issues 
;; in the running system.
;;
;; USAGE:
;;   cat <<'EOF' | agent-tools/eval-app
;;   (your-code-here)
;;   EOF
;;
;;   cat code.clj | agent-tools/eval-app
;;
;; OPTIONS:
;;   --host HOST    nREPL host (default: localhost)
;;   --port PORT    nREPL port (default: 4000)
;;   --timeout MS   Timeout in milliseconds (default: 30000)
;;   --help, -h     Show help
;;
;; EXAMPLES:
;;
;;   # Get the current database value
;;   cat <<'EOF' | agent-tools/eval-app
;;   (dev/db)
;;   EOF
;;
;;   # Query an entity
;;   cat <<'EOF' | agent-tools/eval-app
;;   (dev/show-entity 12345)
;;   EOF
;;
;;   # Check system state
;;   cat <<'EOF' | agent-tools/eval-app
;;   (keys @app.system/state)
;;   EOF
;;
;;   # Multi-line code
;;   cat <<'EOF' | agent-tools/eval-app
;;   (d/q '[:find ?e :where [?e :user/email]] (dev/db))
;;   EOF
;;
;; OUTPUT:
;;   Returns the result of evaluating the Clojure code, pretty-printed.
;;   Errors are printed to stderr.
;;
;; =============================================================================

(require '[babashka.cli :as cli]
         '[clojure.string :as str]
         '[bencode.core :as bencode])

(import '[java.net Socket]
        '[java.io PushbackInputStream])

(def cli-spec
  {:host    {:desc "nREPL host"
             :default "localhost"}
   :port    {:desc "nREPL port"
             :default 4000
             :coerce :int}
   :timeout {:desc "Timeout in milliseconds"
             :default 30000
             :coerce :int}
   :help    {:desc "Show help"
             :alias :h}})

(defn print-help []
  (println "eval-app - Evaluate Clojure code in the running app")
  (println)
  (println "Usage: cat <<'EOF' | agent-tools/eval-app [OPTIONS]")
  (println "       (your-code-here)")
  (println "       EOF")
  (println)
  (println "       cat code.clj | agent-tools/eval-app [OPTIONS]")
  (println)
  (println "Options:")
  (println "  --host HOST    nREPL host (default: localhost)")
  (println "  --port PORT    nREPL port (default: 4000)")
  (println "  --timeout MS   Timeout in milliseconds (default: 30000)")
  (println "  --help, -h     Show this help")
  (println)
  (println "Examples:")
  (println "  cat <<'EOF' | agent-tools/eval-app")
  (println "  (dev/db)")
  (println "  EOF"))

(defn bytes->str [x]
  (if (bytes? x)
    (String. ^bytes x "UTF-8")
    x))

(defn parse-response [response]
  (into {}
        (map (fn [[k v]]
               [(keyword (bytes->str k))
                (if (sequential? v)
                  (mapv bytes->str v)
                  (bytes->str v))])
             response)))

(defn nrepl-eval [{:keys [host port timeout]} code]
  (let [socket (Socket. ^String host ^int port)
        _ (.setSoTimeout socket timeout)
        out (.getOutputStream socket)
        in (PushbackInputStream. (.getInputStream socket))
        session-id (str (random-uuid))
        msg {"op" "eval"
             "code" code
             "id" session-id}]
    (try
      (bencode/write-bencode out msg)
      (loop [has-error false]
        (let [response (parse-response (bencode/read-bencode in))]
          (when-let [out-str (:out response)]
            (print out-str)
            (flush))
          (when-let [err-str (:err response)]
            (binding [*out* *err*]
              (print err-str)
              (flush)))
          (when-let [value (:value response)]
            (println value))
          (when-let [ex (:ex response)]
            (binding [*out* *err*]
              (println "Exception:" ex)))
          (let [status (set (:status response))
                has-error (or has-error
                              (contains? status "error")
                              (contains? status "eval-error"))]
            (if (contains? status "done")
              (if has-error 1 0)
              (recur has-error)))))
      (finally
        (.close socket)))))

(defn eval-code [opts code]
  (try
    (nrepl-eval opts code)
    (catch java.net.ConnectException e
      (binding [*out* *err*]
        (println "Error: Cannot connect to nREPL at" (str (:host opts) ":" (:port opts)))
        (println "Make sure the app is running (bin/dev up)"))
      1)
    (catch java.net.SocketTimeoutException e
      (binding [*out* *err*]
        (println "Error: nREPL request timed out"))
      1)
    (catch Exception e
      (binding [*out* *err*]
        (println "Error:" (.getMessage e)))
      1)))

(let [{:keys [opts]} (cli/parse-args *command-line-args* {:spec cli-spec})
      opts-with-defaults (merge {:host "localhost" :port 4000 :timeout 30000} opts)]
  (if (:help opts)
    (print-help)
    (let [code (slurp *in*)]
      (if (str/blank? code)
        (do (binding [*out* *err*]
              (println "Error: No code provided on stdin")
              (println "Usage: cat <<'EOF' | agent-tools/eval-app")
              (println "       (dev/db)")
              (println "       EOF")
              (println "Run with --help for more information"))
            (System/exit 1))
        (System/exit (eval-code opts-with-defaults code))))))