add :break-on-max-column-alignment-width? option

Author: sirmspencer

README.md

@@ -339,6 +339,28 @@ In order to load the standard configuration file from Leiningen, add the
    :long-name 4} ;; ends past column 7, 1 space
   ```
 
+* `:break-on-max-column-alignment-width?` -
+  true if cljfmt should move a value onto its own line, indented under
+  the keys, when its key ends past the column set by
+  `:max-column-alignment-width`, rather than falling back to a single
+  space on the same line. Has no effect unless
+  `:max-column-alignment-width` is also set. Defaults to false.
+  **Experimental.**
+
+  ```clojure
+  ;; Input:
+  {:a 1
+   :bb 2
+   :ccccccc 3}
+
+  ;; With :align-map-columns? true, :max-column-alignment-width 4,
+  ;; and :break-on-max-column-alignment-width? true:
+  {:a  1        ;; ends within column 4, padded to value column
+   :bb 2        ;; ends at column 4, sets the value column
+   :ccccccc     ;; ends past column 4, value moves to its own line
+   3}
+  ```
+
 * `:blank-lines-separate-alignment?` -
   true if cljfmt should treat blank lines as separators when aligning
   columns. When enabled, alignment groups are separated by blank lines,

cljfmt/src/cljfmt/core.cljc

@@ -386,6 +386,7 @@
    :max-column-alignment-width            nil
    :blank-line-forms                      blank-line-forms
    :blank-lines-separate-alignment?       false
+   :break-on-max-column-alignment-width?  false
    :extra-aligned-forms                   {}
    :extra-blank-line-forms                {}
    :extra-indents                         {}
@@ -671,16 +672,31 @@
 (defn- count-spaces [zloc]
   (if (space? zloc) (node-str-length zloc) 0))
 
-(defn- pad-to-position [zloc start-position {max-gap     :max-column-alignment-gap
-                                             align-width :max-column-alignment-width}]
-  {:pre [(or (nil? max-gap) (pos-int? max-gap))
-         (or (nil? align-width) (pos-int? align-width))]}
+(defn- break-to-own-line [zloc]
+  (let [indent (coll-indent zloc)]
+    (-> zloc
+        z/left*
+        (z/replace* (n/newlines 1))
+        z/right*
+        (z/insert-left* (whitespace indent)))))
+
+(defn- pad-to-position [zloc {:keys [position threshold]}
+                        {max-gap :max-column-alignment-gap
+                         break?  :break-on-max-column-alignment-width?}]
+  {:pre [(or (nil? max-gap) (pos-int? max-gap))]}
   (let [old-gap (count-spaces (z/left* zloc))
-        delta   (- start-position (margin zloc))
-        new-gap (+ old-gap delta)]
-    (if (or (< new-gap 1)
-            (and max-gap (> new-gap max-gap)))
+        delta   (- position (margin zloc))
+        new-gap (+ old-gap delta)
+        key-end (- (margin zloc) old-gap)]
+    (cond
+      (and break? threshold (> key-end threshold))
+      (break-to-own-line zloc)
+
+      (or (< new-gap 1)
+          (and max-gap (> new-gap max-gap)))
       (pad-node zloc (- 1 old-gap))
+
+      :else
       (pad-node zloc delta))))
 
 (defn- edit-column [zloc column f]
@@ -726,9 +742,10 @@
                       positions))
         positions (reduce-fn zloc collector [])
         threshold (when align-width (+ (apply min 0 positions) align-width))]
-    (inc (apply max 0 (if threshold
-                        (filter #(<= % threshold) positions)
-                        positions)))))
+    {:position  (inc (apply max 0 (if threshold
+                                    (filter #(<= % threshold) positions)
+                                    positions)))
+     :threshold threshold}))
 
 (defn- align-one-column
   [zloc col {:keys [blank-lines-separate-alignment?] :as opts}]

cljfmt/test/cljfmt/core_test.cljc

@@ -3234,6 +3234,56 @@
           :max-column-alignment-width 7
           :max-column-alignment-gap   3}))))
 
+(deftest test-break-on-max-column-alignment-width
+  (testing "form: the one outlier value is moved to its own line, indented under the bindings"
+    (is (reformats-to?
+         ["(let [a 1"
+          "      bb 2"
+          "      ccccccc 3]"
+          "  body)"]
+         ["(let [a  1"
+          "      bb 2"
+          "      ccccccc"
+          "      3]"
+          "  body)"]
+         {:align-form-columns?                  true
+          :max-column-alignment-width           8
+          :break-on-max-column-alignment-width? true})))
+  (testing "map: the one outlier value is moved to its own line, indented under the keys"
+    (is (reformats-to?
+         ["{:a \"x\""
+          " :bb \"y\""
+          " :ccccccc \"z\"}"]
+         ["{:a  \"x\""
+          " :bb \"y\""
+          " :ccccccc"
+          " \"z\"}"]
+         {:align-map-columns?                   true
+          :max-column-alignment-width           4
+          :break-on-max-column-alignment-width? true})))
+  (testing "no effect when :max-column-alignment-width is not set"
+    (is (reformats-to?
+         ["{:x 1"
+          " :longer 2}"]
+         ["{:x 1"
+          " :longer 2}"]
+         {:align-map-columns?                   true
+          :max-column-alignment-gap             5
+          :break-on-max-column-alignment-width? true})))
+  (testing "value already on its own line is left alone (idempotent)"
+    (is (reformats-to?
+         ["{:a  1"
+          " :bb 2"
+          " :ccccccc"
+          " 3}"]
+         ["{:a  1"
+          " :bb 2"
+          " :ccccccc"
+          " 3}"]
+         {:align-map-columns?                   true
+          :max-column-alignment-width           4
+          :break-on-max-column-alignment-width? true}))))
+
 (deftest test-realign-form
   (is (= "
 {:x   1