Indent a form on the line after its reader prefix

CHANGELOG.md

@@ -26,6 +26,7 @@
 - [#161](https://github.com/clojure-emacs/clojure-ts-mode/pull/161): Fix converting collections with metadata: a quoted list with metadata after the quote (`'^:foo (1 2)`) failed to convert, and converting to a quoted list put the quote after the metadata.
 - [#153](https://github.com/clojure-emacs/clojure-ts-mode/pull/153): Align threading macro arguments with the first argument instead of the previous one, which went wrong after a line with several forms or a trailing comment.
 - [#154](https://github.com/clojure-emacs/clojure-ts-mode/pull/154): Fix semantic indentation of forms with metadata or a comment before an argument or the body, like `(doto ^Foo`, `(let ;; bindings` or `(comment ;; scratch`.
+- [#155](https://github.com/clojure-emacs/clojure-ts-mode/pull/155): Fix indentation of a form on the line after its reader prefix (`'`, `` ` ``, `~`, `~@`, `@`, `#'`, `#=`), which no rule matched.
 
 ## 0.6.0 (2025-12-02)
 

clojure-ts-mode.el

@@ -1214,6 +1214,31 @@ The possible values for this variable are
            (const :tag "Simple fixed indentation rules." fixed))
   :package-version '(clojure-ts-mode . "0.2.0"))
 
+(defconst clojure-ts--reader-prefix-node-regexp
+  (rx bol (or "quoting_lit" "syn_quoting_lit" "unquoting_lit" "unquote_splicing_lit"
+              "derefing_lit" "var_quoting_lit" "evaling_lit")
+      eol)
+  "Node types of a form behind a reader prefix.
+These are quote, syntax quote, unquote, unquote-splicing, deref, var
+quote and read-eval.")
+
+(defun clojure-ts--prefixed-form-indent (prefixed)
+  "Return (ANCHOR . OFFSET) for PREFIXED as if it started a line.
+
+PREFIXED is a node like @form.  When the form itself starts
+on the line after the prefix, it is indented the way PREFIXED would be."
+  (treesit-simple-indent prefixed
+                         (treesit-node-parent prefixed)
+                         (treesit-node-start prefixed)))
+
+(defun clojure-ts--anchor-prefixed-form (_node parent _bol)
+  "Return the anchor of PARENT, a prefixed form, as if it started a line."
+  (car (clojure-ts--prefixed-form-indent parent)))
+
+(defun clojure-ts--offset-prefixed-form (_node parent _bol)
+  "Return the offset of PARENT, a prefixed form, as if it started a line."
+  (or (cdr (clojure-ts--prefixed-form-indent parent)) 0))
+
 (defvar clojure-ts--fixed-indent-rules
   ;; This is in contrast to semantic
   ;; fixed-indent-rules come from https://tonsky.me/blog/clojurefmt/
@@ -1234,7 +1259,11 @@ The possible values for this variable are
      ((parent-is "^map_lit$") parent 1)
      ((parent-is "^list_lit$") parent 1)
      ((parent-is "^set_lit$") parent 2)
-     ((parent-is "^ns_map_lit$") (nth-sibling 2) 1))))
+     ((parent-is "^ns_map_lit$") (nth-sibling 2) 1)
+     ;; A form on the line after its reader prefix, e.g. @ at the end of a line.
+     ((parent-is ,clojure-ts--reader-prefix-node-regexp)
+      clojure-ts--anchor-prefixed-form
+      clojure-ts--offset-prefixed-form))))
 
 (defvar clojure-ts--semantic-indent-rules-defaults
   '(("alt!"            . ((:block 0)))
@@ -1623,6 +1652,10 @@ used."
      ((parent-is "^read_cond_lit$") parent 3)
      ((parent-is "^tagged_or_ctor_lit$") parent 0)
      ((parent-is "^ns_map_lit$") (nth-sibling 2) 1)
+     ;; A form on the line after its reader prefix, e.g. @ at the end of a line.
+     ((parent-is ,clojure-ts--reader-prefix-node-regexp)
+      clojure-ts--anchor-prefixed-form
+      clojure-ts--offset-prefixed-form)
      ;; https://guide.clojure.style/#body-indentation
      (clojure-ts--match-form-body clojure-ts--anchor-parent-opening-paren 2)
      ;; https://guide.clojure.style/#vertically-align-fn-args

test/clojure-ts-mode-indentation-test.el

@@ -716,6 +716,31 @@ DESCRIPTION is a string with the description of the spec."
     x)]
   (f 1))")
 
+  (it "should indent a form on the line after its reader prefix"
+    ;; No rule used to match these lines, so they kept whatever indentation
+    ;; they had.  Start from no indentation at all.
+    (dolist (expected '("
+(def table
+  ['
+   [identity int? pos-int?]
+   [0 true false]])"
+                        "
+`(let [y# ~
+       x]
+   y#)"
+                        "
+(swap! state assoc :n @
+       (:counter state))"
+                        "
+{:get #'
+ handle-get}"
+                        "
+(def q '
+  (a b c))"))
+      (with-clojure-ts-buffer (replace-regexp-in-string "\n +" "\n" expected)
+        (indent-region (point-min) (point-max))
+        (expect (buffer-string) :to-equal expected))))
+
   (it "should pick up dynamic indentation rules from clojure-ts-get-indent-function"
     (with-clojure-ts-buffer "
 (defmacro my-with-in-str
@@ -775,6 +800,20 @@ DESCRIPTION is a string with the description of the spec."
    (java.util Date
      UUID)))")
 
+  (it "should indent a form on the line after its reader prefix in fixed style"
+    (dolist (expected '("
+(swap! state assoc :n @
+  (:counter state))"
+                        "
+['
+ [a b]]"))
+      (with-temp-buffer
+        (let ((clojure-ts-indent-style 'fixed))
+          (clojure-ts-mode)
+          (insert (replace-regexp-in-string "\n +" "\n" expected))
+          (indent-region (point-min) (point-max))
+          (expect (buffer-string) :to-equal expected)))))
+
   (when-indenting-fixed-it "should indent namespaced maps correctly"
     "
 #:foo{:bar 1