ad5affe89f
Two pre-existing issues in the nrepl command, exposed when #269 moved the accept loop into a future. jolt.nrepl/start was invoked inside (future ...), so binding the socket happened on a background thread. A bind failure such as the port already being in use was captured into a future that nothing derefs and silently swallowed, leaving the main thread parked in run-main-pump forever with no server and no error. start now binds the socket synchronously before returning, so that failure propagates to the caller and the process exits with a visible message. Only the blocking accept loop runs on a worker thread. There was also no shutdown path: the accept loop ran forever and the listen socket was never closed. start now returns a stop fn that breaks the accept loop, closes the socket to free the port, and removes .nrepl-port. main.clj runs run-main-pump and then calls the stop fn, so a stop-main-pump (from a glimmer app on quit, or from nrepl-evaluated code) shuts the server down cleanly and the process exits.
260 lines
13 KiB
Clojure
260 lines
13 KiB
Clojure
(ns jolt.nrepl
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"A minimal, extensible nREPL server for jolt, so an editor (CIDER / Calva /
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Cursive) can connect and develop a project live. Speaks bencode over a loopback
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TCP socket bound through jolt.ffi. Built in: clone, describe, eval, load-file,
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close — enough to connect and eval, with the project's deps on the roots and
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native libs loaded (jolt.main applies the project first), so (require '[lib])
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works.
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EXTENSIBLE: a library can add the heavier nREPL features (sessions,
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interruptible-eval, completion, lookup) as MIDDLEWARE without bloating core. A
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middleware is `(fn [handler] (fn [request] ...))`; list them in deps.edn under
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:nrepl/middleware (symbols resolving to a middleware fn, or to a vector of them)
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and jolt.nrepl composes them over the built-in handler. The request is the
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decoded bencode map (string keys: \"op\" \"code\" \"ns\" \"id\" \"session\" …)
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plus :reply — a thread-safe (fn [response-map]) that adds id/session and sends.
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Public seam for middleware: respond, evaluate, register-ops!, new-session.
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Writes .nrepl-port in the project dir so editors auto-detect the port."
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(:require [clojure.string :as str]
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[clojure.java.io :as io]
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[jolt.ffi :as ffi]))
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;; --- sockets (loopback server) ---------------------------------------------
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;; Load libc (the running process's symbols) BEFORE the foreign-fn bindings below
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;; — defcfn resolves the C entry point when the def is evaluated (at ns load), so
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;; the socket symbols must already be available.
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(ffi/load-library)
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(ffi/defcfn c-socket "socket" [:int :int :int] :int)
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(ffi/defcfn c-bind "bind" [:int :pointer :int] :int)
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(ffi/defcfn c-listen "listen" [:int :int] :int)
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(ffi/defcfn c-setsockopt "setsockopt" [:int :int :int :pointer :int] :int)
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(ffi/defcfn c-accept "accept" [:int :pointer :pointer] :int :blocking)
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(ffi/defcfn c-recv "recv" [:int :pointer :size_t :int] :ssize_t :blocking)
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(ffi/defcfn c-send "send" [:int :pointer :size_t :int] :ssize_t :blocking)
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(ffi/defcfn c-close "close" [:int] :int)
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(def ^:private AF-INET 2)
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(def ^:private SOCK-STREAM 1)
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(def ^:private macos?
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(str/includes? (str/lower-case (or (System/getProperty "os.name") "")) "mac"))
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(def ^:private sol-socket (if macos? 0xffff 1))
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(def ^:private so-reuse (if macos? 4 2))
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(defn- make-sockaddr [port]
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(let [sa (ffi/alloc 16)]
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(dotimes [i 16] (ffi/write sa :uint8 i 0))
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(if macos?
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(do (ffi/write sa :uint8 0 16) (ffi/write sa :uint8 1 AF-INET))
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(ffi/write sa :uint8 0 AF-INET))
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(ffi/write sa :uint8 2 (bit-and (bit-shift-right port 8) 0xff))
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(ffi/write sa :uint8 3 (bit-and port 0xff))
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(ffi/write sa :uint8 4 127) (ffi/write sa :uint8 7 1) ; 127.0.0.1
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sa))
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(defn- listen-socket [port]
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(ffi/load-library) ; libc process symbols
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(let [fd (c-socket AF-INET SOCK-STREAM 0)]
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(when (neg? fd) (throw (ex-info "socket() failed" {})))
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(let [opt (ffi/alloc 4)] (ffi/write opt :int 0 1) (c-setsockopt fd sol-socket so-reuse opt 4) (ffi/free opt))
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(let [sa (make-sockaddr port)]
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(when (neg? (c-bind fd sa 16)) (c-close fd) (ffi/free sa) (throw (ex-info (str "bind() failed on port " port) {})))
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(ffi/free sa))
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(when (neg? (c-listen fd 16)) (c-close fd) (throw (ex-info "listen() failed" {})))
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fd))
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;; bytes flow as latin1 strings on the wire (1 char = 1 byte). Text fields that
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;; may carry unicode (code / value / out) convert at the boundary.
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(defn- ->wire [s] (String. (.getBytes (str s) "UTF-8") "ISO-8859-1"))
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(defn- wire-> [s] (String. (byte-array (map int s)) "UTF-8"))
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(def ^:private bufsize 65536)
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(defn- recv-str [fd]
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(let [buf (ffi/alloc bufsize)]
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(try (let [n (c-recv fd buf bufsize 0)]
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(when (pos? n) (String. (ffi/read-array buf n) "ISO-8859-1")))
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(finally (ffi/free buf)))))
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(defn- send-str [fd s]
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(let [data (byte-array (map int s)) n (alength data) buf (ffi/alloc (max 1 n))]
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(try (ffi/write-array buf data)
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(loop [off 0] (when (< off n) (let [sent (c-send fd (+ buf off) (- n off) 0)]
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(when (pos? sent) (recur (+ off sent))))))
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(finally (ffi/free buf)))))
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;; --- bencode ---------------------------------------------------------------
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(defn- bencode [v]
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(cond
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(integer? v) (str "i" v "e")
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(string? v) (let [w (->wire v)] (str (count w) ":" w))
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(keyword? v) (let [w (->wire (name v))] (str (count w) ":" w))
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(map? v) (str "d" (apply str (mapcat (fn [[k val]] [(bencode (name k)) (bencode val)])
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(sort-by #(name (first %)) v))) "e")
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(or (seq? v) (vector? v)) (str "l" (apply str (map bencode v)) "e")
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(nil? v) "0:"
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:else (let [w (->wire (str v))] (str (count w) ":" w))))
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;; decode one value from `s` at index `i` -> [value next-index], or nil if the
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;; buffer doesn't yet hold a complete value.
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(defn- bdecode [s i]
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(when (< i (count s))
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(let [c (nth s i)]
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(cond
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(= c \i) (let [e (str/index-of s "e" i)]
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(when e [(parse-long (subs s (inc i) e)) (inc e)]))
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(= c \l) (loop [j (inc i) acc []]
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(cond (>= j (count s)) nil
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(= (nth s j) \e) [acc (inc j)]
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:else (let [r (bdecode s j)] (when r (recur (second r) (conj acc (first r)))))))
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(= c \d) (loop [j (inc i) acc {}]
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(cond (>= j (count s)) nil
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(= (nth s j) \e) [acc (inc j)]
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:else (let [k (bdecode s j)]
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(when k (let [val (bdecode s (second k))]
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(when val (recur (second val) (assoc acc (wire-> (first k)) (first val)))))))))
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(and (char? c) (>= (int c) 48) (<= (int c) 57)) ; string: <len>:<bytes>
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(let [colon (str/index-of s ":" i)]
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(when colon
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(let [n (parse-long (subs s i colon)) start (inc colon) end (+ start n)]
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(when (<= end (count s)) [(subs s start end) end]))))
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:else nil))))
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;; --- public seam for middleware --------------------------------------------
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(def ^:private session-counter (atom 0))
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(defn new-session
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"A fresh session id (middleware that implements sessions uses this)."
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[] (str "jolt-" (swap! session-counter inc)))
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(defn respond
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"Send a response map for `request` (id/session added, then bencoded)."
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[request m] ((:reply request) m))
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(defn err-msg
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"Best-effort message for any thrown value (ex-info, or a raw Chez condition —
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ex-message is nil for those, so fall back to the host condition text)."
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[e]
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(or (ex-message e)
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(try ((resolve 'jolt.host/condition-message) e) (catch :default _ nil))
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(pr-str e)))
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(defn evaluate
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"Evaluate `code` (optionally in loaded ns `ns-str`), capturing *out*. Returns
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{:value .. :out .. :ns .. :err ..}. in-ns — not (binding [*ns* ..]) — sets the
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ns load-string resolves against on jolt. Reusable by eval middleware."
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[code ns-str]
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(let [result (atom nil) err (atom nil)
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out (with-out-str
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(try (when (and ns-str (not (str/blank? ns-str)) (find-ns (symbol ns-str)))
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(in-ns (symbol ns-str)))
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(reset! result (load-string code))
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(catch :default e (reset! err (err-msg e)))))]
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{:value (when (nil? @err) (pr-str @result))
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:out out
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:ns (str (ns-name *ns*))
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:err @err}))
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;; ops middleware advertise via describe (built-ins + any a library registers).
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(def ^:private extra-ops (atom #{}))
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(defn register-ops!
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"Register op name(s) so `describe` advertises them. Call at middleware load."
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[& ops] (swap! extra-ops into (map name ops)))
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;; --- built-in handler ------------------------------------------------------
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(defn- built-in-handler [request]
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(let [op (get request "op")]
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(cond
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(= op "clone") (respond request {"new-session" (new-session) "status" ["done"]})
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(= op "close") (respond request {"status" ["session-closed" "done"]})
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(= op "describe") (respond request {"status" ["done"]
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"versions" {"jolt-nrepl" {"major" 0 "minor" 1}}
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"ops" (zipmap (into #{"clone" "close" "describe" "eval" "load-file"}
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@extra-ops)
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(repeat {}))})
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(or (= op "eval") (= op "load-file"))
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(let [code (wire-> (if (= op "load-file") (get request "file") (get request "code")))
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{:keys [value out ns err]} (evaluate code (get request "ns"))]
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(when (seq out) (respond request {"out" out}))
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(if err
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(do (respond request {"err" (str err "\n")})
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(respond request {"ex" (str err) "status" ["eval-error" "done"]}))
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(respond request {"value" value "ns" ns "status" ["done"]})))
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:else (respond request {"status" ["done" "unknown-op"]}))))
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;; --- middleware composition ------------------------------------------------
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;; resolve deps.edn :nrepl/middleware symbols to middleware fns. An entry may
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;; resolve to a single (fn [handler] handler') or to a vector of them (so a
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;; library can export one `default-middleware` var).
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(defn- resolve-middleware [syms]
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(vec (mapcat
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(fn [sym]
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(require (symbol (namespace sym)))
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(let [v (deref (resolve sym))]
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(if (sequential? v) (map #(if (var? %) (deref %) %) v) [v])))
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syms)))
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(defn- build-handler [middleware]
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;; first listed middleware is outermost.
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(reduce (fn [h mw] (mw h)) built-in-handler (reverse middleware)))
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(defn- handle-conn [fd handler]
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;; one send lock per connection: eval/session middleware reply from other
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;; threads, so sends must not interleave.
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(let [lock (Object.)
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reply-for (fn [msg]
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(let [id (get msg "id") session (or (get msg "session") "none")]
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(fn [m]
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(locking lock
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(send-str fd (bencode (cond-> m id (assoc "id" id)
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session (assoc "session" session))))))))]
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(loop [buf ""]
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(let [chunk (recv-str fd)]
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(if (nil? chunk)
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(c-close fd)
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(let [rest-buf (loop [b (str buf chunk)]
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(let [r (bdecode b 0)]
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(if (nil? r) b
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(do (when (map? (first r))
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(let [msg (first r)]
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(try (handler (assoc msg :reply (reply-for msg)))
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(catch :default e (println "nrepl handler error:" (err-msg e))))))
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(recur (subs b (second r)))))))]
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(recur rest-buf)))))))
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(defn start
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"Start the nREPL server on `port` (a concrete port; loopback only). `middleware`
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is a vector of deps.edn :nrepl/middleware symbols to compose over the built-in
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handler.
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Binds the socket synchronously, so a startup failure (e.g. the port is already
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in use) is thrown to the caller rather than swallowed by the accept thread, then
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accepts connections on a background thread and returns immediately. Writes
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.nrepl-port. Does NOT block — the caller keeps the process alive (jolt.main
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parks the main thread in jolt.host/run-main-pump).
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Returns a zero-arg stop fn: it stops the accept loop, closes the listen socket
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(freeing the port), and removes .nrepl-port. Calling it more than once is a
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no-op."
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([port] (start port nil))
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([port middleware]
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(let [handler (build-handler (resolve-middleware (or middleware [])))
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fd (listen-socket port) ; throws on bind/listen failure
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stopped (atom false)]
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(try (spit ".nrepl-port" (str port)) (catch :default _ nil))
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(println (str "nREPL server started on port " port " (127.0.0.1) — .nrepl-port written"))
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(when (seq middleware) (println (str ";; middleware: " (str/join " " middleware))))
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(println ";; connect your editor; ^C to stop")
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(future
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;; A stop closes fd, which makes the blocking accept() return an error; the
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;; @stopped check then breaks the loop instead of spinning on the dead fd.
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(loop []
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(let [conn (c-accept fd ffi/null ffi/null)]
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(when-not @stopped
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(when (>= conn 0)
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(future (try (handle-conn conn handler)
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(catch :default e (println "nrepl conn error:" (err-msg e)) (c-close conn)))))
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(recur)))))
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(fn stop []
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(when (compare-and-set! stopped false true)
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(c-close fd)
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(try (io/delete-file ".nrepl-port" true) (catch :default _ nil)))
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nil))))
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