Add CLI option to parallelize file processing

The files processed by the 'fix' and 'check' commands can be processed
in an arbitrary order and each file can be processed independently, so
the whole process can be parallelized.

To make sure threads aren't writing to stdout/stderr at the same time,
the result for each file is captured and then printed in order once
every file is done. The 'check' command already did this via
print-file-status, the 'fix' command now uses the same mechanism.

Author: or

cljfmt/src/cljfmt/main.clj

@@ -80,6 +80,8 @@
     (when-let [ex (:exception status)]
       (warn "Failed to format file:" path)
       (print-stack-trace ex))
+    (when (:reformatted status)
+      (println "Reformatting" path))
     (when-let [diff (:diff status)]
       (warn path "has incorrect formatting")
       (warn diff))))
@@ -111,34 +113,40 @@
   ([paths]
    (check paths {}))
   ([paths options]
-   (let [counts (transduce
-                 (comp (mapcat (partial find-files options))
-                       (map (partial check-one options))
-                       (map (fn [status]
-                              (print-file-status options status)
-                              (:counts status))))
-                 (completing merge-counts)
-                 paths)]
+   (let [map*   (if (:parallel? options) pmap map)
+         counts (->> paths
+                     (mapcat (partial find-files options))
+                     (map* (partial check-one options))
+                     (map (fn [status]
+                            (print-file-status options status)
+                            (:counts status)))
+                     (reduce merge-counts))]
      (print-final-count counts)
      (exit counts))))
 
+(defn- fix-one [options file]
+  (let [original (slurp file)]
+    (try
+      (let [revised (reformat-string options original)]
+        (if (not= original revised)
+          (do (spit file revised)
+              {:file file :reformatted true})
+          {:file file}))
+      (catch Exception e
+        {:file file :exception e}))))
+
 (defn fix
   "Applies the formatting (as per `options`) to the Clojure files
   contained in `paths`."
   ([paths]
    (fix paths {}))
   ([paths options]
-   (let [files (mapcat (partial find-files options) paths)]
-     (doseq [^java.io.File f files]
-       (let [original (slurp f)]
-         (try
-           (let [revised (reformat-string options original)]
-             (when (not= original revised)
-               (println "Reformatting" (project-path options f))
-               (spit f revised)))
-           (catch Exception e
-             (warn "Failed to format file:" (project-path options f))
-             (print-stack-trace e))))))))
+   (let [map* (if (:parallel? options) pmap map)]
+     (->> paths
+          (mapcat (partial find-files options))
+          (map* (partial fix-one options))
+          (map (partial print-file-status options))
+          dorun))))
 
 (defn- cli-file-reader [filepath]
   (let [contents (slurp filepath)]
@@ -149,7 +157,8 @@
 (def default-options
   {:project-root "."
    :file-pattern #"\.clj[csx]?$"
-   :ansi?        true})
+   :ansi?        true
+   :parallel?    false})
 
 (defn merge-default-options [options]
   (-> (merge default-options options)
@@ -160,6 +169,8 @@
 
 (def ^:private cli-options
   [[nil "--help"]
+   [nil "--parallel"
+    :id :parallel?]
    [nil "--file-pattern FILE_PATTERN"
     :default (:file-pattern default-options)
     :parse-fn re-pattern]
@@ -207,7 +218,9 @@
       (if (or (nil? cmd) (:help options))
         (do (println "cljfmt [OPTIONS] COMMAND [PATHS ...]")
             (println (:summary parsed-opts)))
-        (case cmd
-          "check" (check paths options)
-          "fix"   (fix paths options)
-          (abort "Unknown cljfmt command:" cmd))))))
+        (do (case cmd
+              "check" (check paths options)
+              "fix"   (fix paths options)
+              (abort "Unknown cljfmt command:" cmd))
+            (when (:parallel? options)
+              (shutdown-agents)))))))