[PATCH] Flymake Support Indicator Errors in Margin

[Elijah G <eg642616@gmail.com>]

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Hello developers,
this is my first time contributing to emacs,
i made support for displaying errors in margin for flymake like flycheck
does,
This allows indicating errors in both text and graphical mode.

I've sent my copyright assignment request.

Since this is my first time contributing i would like to hear your
suggestions and thoughts

Thanks.

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From 0d4539c6b8483eb13cfcdde3d73c71e430fdb30b Mon Sep 17 00:00:00 2001
From: Elias G <eg642616@gmail.com>
Date: Mon, 11 Mar 2024 13:35:06 -0600
Subject: [PATCH] Flymake Support Indicator Errors in Margin

---
 etc/NEWS                  |  11 ++++
 lisp/progmodes/flymake.el | 117 +++++++++++++++++++++++++++++++++-----
 2 files changed, 114 insertions(+), 14 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 19cd170e5c7..83cf1ba9962 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1121,6 +1121,17 @@ in a clean environment.
 
 ** Flymake
 
++++
+*** New user option 'flymake-indicator-type'
+Indicate which indicator type to use for display errors.
+
+The value can be nil (dont indicate errors but just highlight them),
+fringes (use fringes) or margins (use margins).
+
++++
+*** Support Display Errors Indicator in margin
+This allow indicate errors in both graphical and text display.
+
 +++
 *** New user option 'flymake-show-diagnostics-at-end-of-line'.
 When non-nil, Flymake shows summarized descriptions of diagnostics at
diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index db00cc59c0e..835f2057109 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -180,6 +180,73 @@ See `flymake-error-bitmap' and `flymake-warning-bitmap'."
 		 (const right-fringe)
 		 (const :tag "No fringe indicators" nil)))
 
+(defcustom flymake-indicator-type 'fringes
+  "Indicate which indicator type to use for display errors.
+
+The value can be nil (dont indicate errors but just highlight them),
+fringes (use fringes) or margins (use margins)
+
+Difference between fringes and margin is that fringes support diplaying
+bitmaps on graphical displays and margins display text in a blank area
+of buffer that works in both graphical and text displays.
+
+See Info node `Fringes' and Info node `(elisp)Display Margins'."
+  :version "30.1"
+  :type '(choice (const :tag "Use Fringes" fringes)
+		 (const :tag "Use Margins "margins)
+		 (const :tag "No indicators" nil)))
+
+(defcustom flymake-error-margin-string '("‼" compilation-error)
+  "String used in the margn for indicating errors.
+The value may also be a list of two elements where the second
+element specifies the face for the string.
+See also `flymake-warning-margin-string'.
+
+The option `flymake-margin-indicator-position' controls how and where
+this is used."
+  :version "30.1"
+  :type '(choice (string :tag "String")
+                 (list :tag "String and face"
+                       (string :tag "String")
+                       (face :tag "Face"))))
+
+(defcustom flymake-warning-margin-string '("!" compilation-warning)
+  "String used in the margin for indicating warnings.
+The value may also be a list of two elements where the second
+element specifies the face for the string.
+See also `flymake-error-margin-string'.
+
+The option `flymake-margin-indicator-position' controls how and where
+this is used."
+  :version "30.1"
+  :type '(choice (string :tag "String")
+                 (list :tag "String and face"
+                       (string :tag "String")
+                       (face :tag "Face"))))
+
+(defcustom flymake-note-margin-string '("!" compilation-info)
+  "String used in the margin for indicating info notes.
+The value may also be a list of two elements where the second
+element specifies the face for the string.
+See also `flymake-error-margin-string'.
+
+The option `flymake-margin-indicator-position' controls how and where
+this is used."
+  :version "30.1"
+  :type '(choice (string :tag "String")
+                 (list :tag "String and face"
+                       (string :tag "String")
+                       (face :tag "Face"))))
+
+(defcustom flymake-margin-indicator-position 'left-margin
+  "The position to put Flymake margin indicator.
+The value can be nil (do not use indicators), `left-margin' or `right-margin'.
+See `flymake-error-margin-string' and `flymake-warning-margin-string'."
+  :version "30.1"
+  :type '(choice (const left-margin)
+		 (const right-margin)
+		 (const :tag "No margin indicators" nil)))
+
 (make-obsolete-variable 'flymake-start-syntax-check-on-newline
 		        "can check on newline in post-self-insert-hook"
                         "27.1")
@@ -630,6 +697,7 @@ Node `(Flymake)Flymake error types'"
 
 (put 'flymake-error 'face 'flymake-error)
 (put 'flymake-error 'flymake-bitmap 'flymake-error-bitmap)
+(put 'flymake-error 'flymake-margin-string 'flymake-error-margin-string)
 (put 'flymake-error 'severity (warning-numeric-level :error))
 (put 'flymake-error 'mode-line-face 'flymake-error-echo)
 (put 'flymake-error 'echo-face 'flymake-error-echo)
@@ -638,6 +706,7 @@ Node `(Flymake)Flymake error types'"
 
 (put 'flymake-warning 'face 'flymake-warning)
 (put 'flymake-warning 'flymake-bitmap 'flymake-warning-bitmap)
+(put 'flymake-warning 'flymake-margin-string 'flymake-warning-margin-string)
 (put 'flymake-warning 'severity (warning-numeric-level :warning))
 (put 'flymake-warning 'mode-line-face 'flymake-warning-echo)
 (put 'flymake-warning 'echo-face 'flymake-warning-echo)
@@ -646,6 +715,7 @@ Node `(Flymake)Flymake error types'"
 
 (put 'flymake-note 'face 'flymake-note)
 (put 'flymake-note 'flymake-bitmap 'flymake-note-bitmap)
+(put 'flymake-note 'flymake-margin-string 'flymake-note-margin-string)
 (put 'flymake-note 'severity (warning-numeric-level :debug))
 (put 'flymake-note 'mode-line-face 'flymake-note-echo)
 (put 'flymake-note 'echo-face 'flymake-note-echo)
@@ -682,19 +752,34 @@ associated `flymake-category' return DEFAULT."
   (flymake--lookup-type-property type 'severity
                                  (warning-numeric-level :error)))
 
-(defun flymake--fringe-overlay-spec (bitmap &optional recursed)
-  (if (and (symbolp bitmap)
-           (boundp bitmap)
-           (not recursed))
-      (flymake--fringe-overlay-spec
-       (symbol-value bitmap) t)
-    (and flymake-fringe-indicator-position
-         bitmap
-         (propertize "!" 'display
-                     (cons flymake-fringe-indicator-position
-                           (if (listp bitmap)
-                               bitmap
-                             (list bitmap)))))))
+(defun flymake--fringe-overlay-spec (indicator)
+  "Return INDICATOR-TYPE as propertized string to use in error indicators"
+  (let* ((value (if (symbolp indicator)
+                    (symbol-value indicator)
+                  indicator))
+         (indicator-car (if (listp value)
+                            (car value)
+                          value))
+         (indicator-cdr (if (listp value)
+                            (cdr value))))
+    (cond
+     ((symbolp indicator-car)
+      (propertize "!" 'display
+                  (cons flymake-fringe-indicator-position
+                        (if (listp value)
+                            value
+                          (list value)))))
+     ((stringp indicator-car)
+      (propertize "!"
+                  'display
+                  `((margin ,flymake-margin-indicator-position)
+                    ,(propertize
+                      indicator-car
+                      'face
+                      `(:inherit (,indicator-cdr
+                                  default)
+                                 )))))
+     (t nil))))
 
 (defun flymake--equal-diagnostic-p (a b)
   "Tell if A and B are equivalent `flymake--diag' objects."
@@ -843,7 +928,11 @@ Return nil or the overlay created."
         (flymake--fringe-overlay-spec
          (flymake--lookup-type-property
           type
-          'flymake-bitmap
+          (cond ((eq flymake-indicator-type 'fringes)
+                 'flymake-bitmap)
+                ((eq flymake-indicator-type 'margins)
+                 'flymake-margin-string)
+                (t nil))
           (alist-get 'bitmap (alist-get type ; backward compat
                                         flymake-diagnostic-types-alist)))))
       ;; (default-maybe 'after-string
-- 
2.44.0.windows.1