Expose repl task dependencies

The repl task is special because it can't run in a pod. It needs to
run in the project context and have access to the environment of the
build.boot script.

In order to keep the project classpath pristine when the REPL is not in
use, the nREPL dependencies are not loaded until the repl task actually
needs to run. This presents difficulties with middleware, since most of
these are in namespaces that assume tools.nrepl is available.

To support middlware in this environment we expose two atoms:

- boot.repl/*default-dependencies* atom containing a vector of maven
  coordinates in the (set-env! :dependencies '[...]) format. These
  dependencies will be added only when the repl task is run, and only if
  the project does not already have explicit dependencies for the deps
  it would otherwise load.

- boot.repl/*default-middleware* atom containing a vector of namespace
  qualified symbols corresponding to desired middleware. The repl task
  will resolve them at runtime as necessary, so they don't need to be
  resolvable from the build.boot.

Modify these to change dependencies or middleware loaded by default by
the repl task. The middleware option to the repl task adds middleware in
addition to these defaults. The handler option will override these.

boot/core/src/boot/repl.clj

@@ -0,0 +1,8 @@
+(ns boot.repl)
+
+(def ^:dynamic *default-dependencies*
+  (atom '[[org.clojure/tools.nrepl "0.2.4"]]))
+
+(def ^:dynamic *default-middleware*
+  (atom ['boot.from.io.aviso.nrepl/pretty-middleware]))
+

boot/core/src/boot/repl_server.clj

@@ -1,6 +1,7 @@
 (ns boot.repl-server
   (:require
    [boot.core                              :as core]
+   [boot.repl                              :as repl]
    [boot.from.io.aviso.nrepl               :as pretty]
    [clojure.java.io                        :as io]
    [clojure.tools.nrepl.server             :as server]
@@ -38,8 +39,6 @@
   #'pretty/pretty-middleware
   {:requires #{} :expects #{}})
 
-(def ^:dynamic *default-middleware* (atom [#'pretty/pretty-middleware]))
-
 (defn ->var
   [thing]
   (if-not (symbol? thing)
@@ -65,7 +64,8 @@
         init-ns        (or init-ns 'boot.user)
         init-ns-mw     [(wrap-init-ns init-ns)]
         user-mw        (->mw-list middleware)
-        middleware     (concat init-ns-mw *default-middleware* user-mw)
+        default-mw     (->mw-list @repl/*default-middleware*)
+        middleware     (concat init-ns-mw default-mw user-mw)
         handler        (if handler
                          (->var handler)
                          (apply server/default-handler middleware))

boot/core/src/boot/task/built_in.clj

@@ -5,6 +5,7 @@
    [clojure.string       :as string]
    [boot.pod             :as pod]
    [boot.file            :as file]
+   [boot.repl            :as repl]
    [boot.core            :as core]
    [boot.main            :as main]
    [boot.util            :as util]
@@ -169,9 +170,10 @@
   If no port is specified the server will choose a random one and the client
   will read the .nrepl-port file and use that.
 
-  The #'boot.repl-server/*default-middleware* dynamic var holds a vector of the
-  default REPL middleware to be included. You may modify this in your build.boot
-  file by calling set! or rebinding the var."
+  The *default-middleware* and *default-dependencies* atoms in the boot.repl-server
+  namespace contain vectors of default REPL middleware and REPL dependencies to
+  be loaded when starting the server. You may modify these in your build.boot
+  file."
 
   [s server         bool  "Start REPL server only."
    c client         bool  "Start REPL client only."
@@ -184,7 +186,7 @@
    p port PORT      int   "The port to listen on and/or connect to."
    n init-ns NS     sym   "The initial REPL namespace."
    m middleware SYM [sym] "The REPL middleware vector."
-   x handler SYM    sym   "The REPL handler, when used middleware option is ignored"]
+   x handler SYM    sym   "The REPL handler (overrides middleware options)."]
 
   (let [srv-opts (select-keys *opts* [:bind :port :init-ns :middleware :handler])
         cli-opts (-> *opts*
@@ -194,11 +196,10 @@
                             :custom-eval eval
                             :custom-init init
                             :skip-default-init skip-init))
-        repl-svr (delay (try (require 'clojure.tools.nrepl.server)
-                             (catch Throwable _
-                               (pod/add-dependencies
-                                 (update-in (core/get-env) [:dependencies]
-                                            conj '[org.clojure/tools.nrepl "0.2.4"]))))
+        deps     (remove pod/dependency-loaded? @repl/*default-dependencies*)
+        repl-svr (delay (when (seq deps)
+                          (pod/add-dependencies
+                            (assoc (core/get-env) :dependencies deps)))
                         (require 'boot.repl-server)
                         ((resolve 'boot.repl-server/start-server) srv-opts))
         repl-cli (delay (pod/call-worker `(boot.repl-client/client ~cli-opts)))]

boot/pod/src/boot/pod.clj

@@ -103,17 +103,36 @@
                first
                (.getInputStream jarfile))))))
 
-(defn pom-properties-map
-  [prop-or-jarpath]
-  (let [prop (if (instance? Properties prop-or-jarpath)
-               prop-or-jarpath
-               (doto (Properties.) (.load (io/input-stream prop-or-jarpath))))
-        gid  (.getProperty prop "groupId")
-        aid  (.getProperty prop "artifactId")]
+(defn- pom-prop-map
+  [props]
+  (let [gid (.getProperty props "groupId")
+        aid (.getProperty props "artifactId")
+        ver (.getProperty props "version")]
     {:group-id    gid
      :artifact-id aid
      :project     (symbol gid aid)
-     :version     (.getProperty prop "version")}))
+     :version     ver}))
+
+(defn dependency-loaded?
+  [[project & _]]
+  (let [[aid gid] (util/extract-ids project)]
+    (io/resource (format "META-INF/maven/%s/%s/pom.properties" aid gid))))
+
+(defn dependency-pom-properties
+  [coord]
+  (doto (Properties.)
+    (.load (io/input-stream (dependency-loaded? coord)))))
+
+(defn dependency-pom-properties-map
+  [coord]
+  (pom-prop-map (dependency-pom-properties coord)))
+
+(defn pom-properties-map
+  [prop-or-jarpath]
+  (pom-prop-map
+    (if (instance? Properties prop-or-jarpath)
+      prop-or-jarpath
+      (doto (Properties.) (.load (io/input-stream prop-or-jarpath))))))
 
 (defn pom-xml
   [jarpath]