Introduce cider-shorten-error-overlays customization option

CHANGELOG.md

@@ -10,6 +10,7 @@
 - [#3522](https://github.com/clojure-emacs/cider/issues/3522): Introduce a new possible value for [`cider-use-overlays`](https://docs.cider.mx/cider/usage/code_evaluation.html#overlays): `errors-only`.
   - If specified, only errors will result in an overlay being shown.
 - [#3527](https://github.com/clojure-emacs/cider/issues/3527): Preserve the font size as one navigates through the CIDER inspector.
+- [#3525](https://github.com/clojure-emacs/cider/issues/3525): Introduce [`cider-inline-error-message-function`](https://docs.cider.mx/cider/usage/code_evaluation.html#overlays) customization option.
 
 ## 1.8.2 (2023-10-15)
 

cider-eval.el

@@ -821,6 +821,26 @@ REPL buffer.  This is controlled via
                                                      conn)))
           (nrepl-dict-get result "phase"))))))
 
+(defcustom cider-inline-error-message-function #'cider--shorten-error-message
+  "A function that will shorten a given error message,
+as shown in overlays / the minibuffer (per `cider-use-overlays').
+
+The function takes a single arg.  You may want to use `identity',
+for leaving the message as-is."
+  :type 'boolean
+  :group 'cider
+  :package-version '(cider . "1.19.0"))
+
+(defun cider--shorten-error-message (err)
+  "Removes from ERR the prefix matched by `cider-clojure-compilation-regexp',
+and the suffix matched by `cider-module-info-regexp'."
+  (thread-last err
+               (replace-regexp-in-string cider-clojure-compilation-regexp
+                                         "")
+               (replace-regexp-in-string cider-module-info-regexp
+                                         "")
+               (string-trim)))
+
 (declare-function cider-inspect-last-result "cider-inspector")
 (defun cider-interactive-eval-handler (&optional buffer place)
   "Make an interactive eval handler for BUFFER.
@@ -856,12 +876,7 @@ when `cider-auto-inspect-after-eval' is non-nil."
                                                  (member phase cider-clojure-compilation-error-phases)))
                                        ;; Display errors as temporary overlays
                                        (let ((cider-result-use-clojure-font-lock nil)
-                                             (trimmed-err (thread-last err
-                                                                       (replace-regexp-in-string cider-clojure-compilation-regexp
-                                                                                                 "")
-                                                                       (replace-regexp-in-string cider-module-info-regexp
-                                                                                                 "")
-                                                                       (string-trim))))
+                                             (trimmed-err (funcall cider-inline-error-message-function err)))
                                          (cider--display-interactive-eval-result
                                           trimmed-err
                                           'error

doc/modules/ROOT/pages/usage/code_evaluation.adoc

@@ -207,6 +207,17 @@ bottom) with the `cider-use-overlays` variable:
 (setq cider-use-overlays nil)
 ----
 
+Overlays that indicate errors are by default trimmed of file/line/phase information.
+
+(Example: the entire `Syntax error compiling at (src/ns.clj:227:3).` preamble)
+
+You can prevent any trimming by customizing instead:
+
+[source,lisp]
+----
+(setq cider-inline-error-message-function #'identity)
+----
+
 By default, result overlays are displayed at the end of the line. You can set
 the variable `cider-result-overlay-position` to display results at the end of
 their respective forms instead.
@@ -217,7 +228,6 @@ Note that this also affects the position of debugger overlays.
 (setq cider-result-overlay-position 'at-point)
 ----
 
-
 You can also customize how overlays are persisted using the variable
 `cider-eval-result-duration`.
 
@@ -228,7 +238,6 @@ Setting the variable to a number represents the duration in seconds until
 overlays are removed, while setting it to `'change' persists overlays until the
 next change to the buffer contents.
 
-
 [source,lisp]
 ----
 (setq cider-eval-result-duration 5.0)