feat: pretty printing without color (#16)

Introduce a new flag `--color` that decides whether colors are printed
while pretty-printing is on. Valid values are `on`, `off` and `auto`,
which is the default. In the future, there is the possibility of
autodetecting from TTY settings, but at the time of writing `auto`
means `on`.

The flags `-c` and `-C` can also be used to toggle color on/off respectively.

NB: Currently, only applies to EDN printing.

Additionally tests the pretty-printing with multiple line case, and
ANSI color escape sequences.

README.md

@@ -76,6 +76,9 @@ Options:
   -i, --in FORMAT                         yaml     Input format: csv, edn, json, lines, msgpack, text, transit, yaml
   -o, --out FORMAT                        edn      Output format: csv, edn, json, lines, msgpack, text, transit, yaml
   -p, --[no-]pretty                                Pretty print output - default is true
+      --color COLOR                       auto     When pretty printing, whether to use colors: auto, off, on - default is auto
+  -c                                               Same as --color=on
+  -C                                               Same as --color=off
   -k, --key-fn FN                         keyword  Function used to transform keys - currently only supported for JSON and CSV
       --yaml-unsafe                                Enables unsafe mode in clj-yaml / SnakeYAML
       --[no-]yaml-keywords                         Turn map keys into keywords in clj-yaml - default is true

src/cq/formats.clj

@@ -35,11 +35,13 @@
     (edn/read (PushbackReader. (io/reader in)))))
 
 (defn ->edn-writer
-  [{:keys [pretty]}]
+  [{:keys [pretty color]}]
   (if pretty
     (fn [x out]
       (binding [*out* (io/writer out)]
-        (puget/cprint x)))
+        (if color
+          (puget/cprint x)
+          (puget/pprint x))))
     (fn [x out]
       (binding [*out* (io/writer out)]
         (pr x)

src/cq/main.clj

@@ -7,6 +7,10 @@
 
 (require 'cq.readers)
 
+(def colors #{:auto :on :off})
+
+(def colors-str (str/join ", " (sort (map name colors))))
+
 (def formats (set (keys fmt/formats)))
 
 (def formats-str (str/join ", " (sort formats)))
@@ -24,6 +28,16 @@
     :validate [formats]]
    ["-p" "--[no-]pretty" "Pretty print output - default is true"
     :default true]
+   [nil "--color COLOR" (str "When pretty printing, whether to use colors: " colors-str " - default is auto")
+    :default "auto"
+    :parse-fn keyword
+    :validate [colors]]
+   ["-c" nil "Same as --color=on"
+    :id :color
+    :assoc-fn (fn [m _ _] (assoc m :color :on))]
+   ["-C" nil "Same as --color=off"
+    :id :color
+    :assoc-fn (fn [m _ _] (assoc m :color :off))]
    ["-k" "--key-fn FN" "Function used to transform keys - currently only supported for JSON and CSV"
     :default "keyword"]
    [nil "--yaml-unsafe" "Enables unsafe mode in clj-yaml / SnakeYAML"]
@@ -96,11 +110,18 @@
 (def ^:dynamic *stdin* System/in)
 (def ^:dynamic *stdout* System/out)
 
+(defn- handle-auto-options [opts]
+  (update opts :color #(case %
+                         :auto true ; would be nice to detect
+                         :on true
+                         false)))
+
 (defn main
   [args]
   (let [{:keys [arguments exit-message ok?]
          {:keys [in out] :as opts} :options}
-        (validate-args args)]
+        (validate-args args)
+        opts (handle-auto-options opts)]
     (if exit-message
       (exit (if ok? 0 1) exit-message)
       (let [expressions (args->exprs arguments)

test/cq/formats_test.clj

@@ -60,7 +60,25 @@
     (is (= {:a {:b [1 2 3]}} (test-reader-str sut/->edn-reader nil "{:a {:b [1 2 3]}}"))))
 
   (testing "writer"
-    (is (= "{:a {:b [1 2 3]}}\n" (test-writer-str sut/->edn-writer nil {:a {:b [1 2 3]}})))))
+    (is (= "{:a {:b [1 2 3]}}\n" (test-writer-str sut/->edn-writer nil {:a {:b [1 2 3]}})))
+
+    (testing "pretty"
+      (is (= "{:a {:b [1 2 3],\n     :c [2 3 {:something :long}],\n     :d [1 2 {:something :even/longer}]}}\n"
+             (test-writer-str sut/->edn-writer {:pretty true :color false} {:a {:b [1 2 3] :c [2 3 {:something :long}] :d [1 2 {:something :even/longer}]}})))
+
+      (testing "color"
+        (is (= "\u001B[1;31m{\u001B[0m\u001B[1;33m:a\u001B[0m \u001B[1;31m{\u001B[0m\u001B[1;33m:b\u001B[0m \u001B[1;31m[\u001B[0m\u001B[36m1\u001B[0m \u001B[36m2\u001B[0m \u001B[36m3\u001B[0m\u001B[1;31m]\u001B[0m,\n     \u001B[1;33m:c\u001B[0m \u001B[1;31m[\u001B[0m\u001B[36m2\u001B[0m \u001B[36m3\u001B[0m \u001B[1;31m{\u001B[0m\u001B[1;33m:something\u001B[0m \u001B[1;33m:long\u001B[0m\u001B[1;31m}\u001B[0m\u001B[1;31m]\u001B[0m,\n     \u001B[1;33m:d\u001B[0m \u001B[1;31m[\u001B[0m\u001B[36m1\u001B[0m \u001B[36m2\u001B[0m \u001B[1;31m{\u001B[0m\u001B[1;33m:something\u001B[0m \u001B[1;33m:even/longer\u001B[0m\u001B[1;31m}\u001B[0m\u001B[1;31m]\u001B[0m\u001B[1;31m}\u001B[0m\u001B[1;31m}\u001B[0m\n"
+               (test-writer-str sut/->edn-writer {:pretty true :color true} {:a {:b [1 2 3] :c [2 3 {:something :long}] :d [1 2 {:something :even/longer}]}})))))))
+
+(comment
+  ;; simple utility for printing an ANSI escaped sequence for a test constant
+  ;; ANSI uses the ESC character for escape codes and it is lost in printing
+  (let [x {:a {:b [1 2 3] :c [2 3 {:something :long}] :d [1 2 {:something :even/longer}]}}
+        s (test-writer-str sut/->edn-writer {:pretty true :color true} x)]
+    (str/join (for [c s]
+                (if (= 27 (int c))
+                  "ESC" ; replace with \u001B and you get a test constant
+                  c)))))
 
 (defn resource->bytes [file]
   (with-open [xin (io/input-stream (io/resource file))