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Add :break-on-max-column-alignment-width? option #426

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2f4affc
Add :max-column-alignment-width option
sirmspencer Jul 24, 2026
b693729
add :break-on-max-column-alignment-width? option
sirmspencer Aug 7, 2026
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45 changes: 45 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,51 @@ In order to load the standard configuration file from Leiningen, add the
:as everything} ;; 27 spaces, falls back to 1 space
```

* `:max-column-alignment-width` -
a positive integer that limits which keys participate in column
alignment. Keys whose end column is at or within N are aligned
together; keys that end past column N are not padded and receive a
single space before their value. Defaults to nil (no limit).
**Experimental.**

```clojure
;; Input:
{:a 1
:abcde 2
:abcdefg 3
:long-name 4}

;; With :align-map-columns? true and :max-column-alignment-width 7:
;; :a and :abcde end at or within column 7 and align together;
;; :abcdefg and :long-name end past column 7 and are not padded
{:a 1 ;; ends within column 7, padded to value column
:abcde 2 ;; ends at column 7, sets the value column
:abcdefg 3 ;; ends past column 7, 1 space
: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,
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54 changes: 41 additions & 13 deletions cljfmt/src/cljfmt/core.cljc
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Expand Up @@ -383,8 +383,10 @@
:align-single-column-lines? false
:aligned-forms default-aligned-forms
:max-column-alignment-gap nil
: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 {}
Expand Down Expand Up @@ -670,13 +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}]
(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 [delta (- start-position (margin zloc))]
(if max-gap
(let [old-gap (count-spaces (z/left* zloc))
new-gap (+ old-gap delta)]
(pad-node zloc (if (> new-gap max-gap) (- 1 old-gap) delta)))
(let [old-gap (count-spaces (z/left* zloc))
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]
Expand Down Expand Up @@ -707,17 +727,25 @@
(recur (z/right* zloc) 0 acc)
(recur (z/right* zloc) (inc col) (f zloc col acc)))))))

(defn- column-start-position [zloc col opts]
(let [reduce-fn (if (:blank-lines-separate-alignment? opts)
(defn- column-start-position
[zloc col {align-width :max-column-alignment-width
align-singles? :align-single-column-lines?
separate? :blank-lines-separate-alignment?}]
(let [reduce-fn (if separate?
reduce-column-group
reduce-columns)
maximizer (fn [zloc c max-pos]
collector (fn [zloc c positions]
(if (and (= c (dec col))
(or (:align-single-column-lines? opts)
(or align-singles?
(not (single-column-line? zloc))))
(max max-pos (node-end-position zloc))
max-pos))]
(inc (reduce-fn zloc maximizer 0))))
(conj positions (node-end-position zloc))
positions))
positions (reduce-fn zloc collector [])
threshold (when align-width (+ (apply min 0 positions) align-width))]
{: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}]
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3 changes: 3 additions & 0 deletions cljfmt/src/cljfmt/main.clj
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Expand Up @@ -26,6 +26,9 @@
[nil "--[no-]blank-lines-separate-alignment"
:default (:blank-lines-separate-alignment? defaults)
:id :blank-lines-separate-alignment?]
[nil "--[no-]break-on-max-column-alignment-width"
:default (:break-on-max-column-alignment-width? defaults)
:id :break-on-max-column-alignment-width?]
[nil "--max-column-alignment-gap"
:default (:max-column-alignment-gap defaults)
:parse-fn #(cond-> % (string? %) parse-long)
Expand Down
91 changes: 91 additions & 0 deletions cljfmt/test/cljfmt/core_test.cljc
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Expand Up @@ -3193,6 +3193,97 @@
{:align-map-columns? true
:max-column-alignment-gap 5}))))

(deftest test-max-column-alignment-width
(testing "form: anchor demoted until all keys fit within width"
(is (reformats-to?
["(let [a 1"
" abcde 2"
" abcdefg 3"
" long-name 4]"
" [a abcde abcdefg long-name])"]
["(let [a 1"
" abcde 2"
" abcdefg 3"
" long-name 4]"
" [a abcde abcdefg long-name])"]
{:align-form-columns? true
:max-column-alignment-width 11})))
(testing "map: anchor demoted until all keys fit within width"
(is (reformats-to?
["{:a \"x\""
" :abcde \"y\""
" :abcdefg \"z\""
" :long-key \"w\"}"]
["{:a \"x\""
" :abcde \"y\""
" :abcdefg \"z\""
" :long-key \"w\"}"]
{:align-map-columns? true
:max-column-alignment-width 7})))
(testing "composing both flags refines alignment further"
(is (reformats-to?
["{:x \"a\""
" :abc \"b\""
" :abcde \"c\""
" :long-key \"d\"}"]
["{:x \"a\""
" :abc \"b\""
" :abcde \"c\""
" :long-key \"d\"}"]
{:align-map-columns? true
: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
Expand Down
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