bug#59626: 29.0.50; [PATCH] comint-fontify-input: Fix field boundary issue

[miha--- via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Please find attached a patch which fixes a minor issue with narrowing to
fields during comint input fontification. The issue didn't cause any
visible bugs that I know of, I only noticed it during experimentation
with tree-sitter integration.

Not that my copyright paperwork renewal is currently in progress, but I
hope that the number of lines in this patch fall below the threshold.


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From 5e2effcaf8d4b1f1cc835fae910e8d85abb7be3c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miha=20Rihtar=C5=A1i=C4=8D?= <miha@kamnitnik.top>
Date: Sat, 26 Nov 2022 23:01:24 +0100
Subject: [PATCH] comint-fontify-input: Fix field boundary issue

* lisp/comint.el (comint--intersect-regions): Don't call field-end if
we are on a field boundary already.
---
 lisp/comint.el | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lisp/comint.el b/lisp/comint.el
index ddb3464891..f47e6089f2 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -4122,9 +4122,15 @@ comint--intersect-regions
         (save-restriction
           (let ((beg2 beg1)
                 (end2 end1))
-            (when (= beg2 beg)
+            (when (and (= beg2 beg)
+                       (> beg2 (point-min))
+                       (eq is-output
+                           (eq (get-text-property (1- beg2) 'field) 'output)))
               (setq beg2 (field-beginning beg2)))
-            (when (= end2 end)
+            (when (and (= end2 end)
+                       (< end2 (point-max))
+                       (eq is-output
+                           (eq (get-text-property (1+ end2) 'field) 'output)))
               (setq end2 (field-end end2)))
             ;; Narrow to the whole field surrounding the region
             (narrow-to-region beg2 end2))
-- 
2.38.1


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