Deprecate option erc-remove-parsed-property

* etc/ERC-NEWS: Add entry for `erc-remove-parsed-property'.
* lisp/erc/erc.el (erc-remove-parsed-property): Deprecate option
because the potential for inadvertent self harm outweighs the
potential benefits.  Additionally, replicating this functionality via
hooks is trivial.
(erc-display-line-1): Remove quasi-deprecated `tags' property because
the preferred format for `erc-response.tags' has changed, and ERC has
never supported IRCv3 tags.

2 files changed, 19 insertions, 2 deletions

diff --git a/etc/ERC-NEWS b/etc/ERC-NEWS
index dca9fff4e65..7c287b9de23 100644
--- a/etc/ERC-NEWS
+++ b/etc/ERC-NEWS
@@ -220,6 +220,14 @@ atop any message.  The new companion option 'erc-echo-timestamp-zone'
 determines the default timezone when not specified with a prefix
 argument.
 
+** Option 'erc-remove-parsed-property' deprecated.
+This option's nil behavior serves no practical purpose yet has the
+potential to degrade the user experience by competing for space with
+forthcoming features powered by next generation extensions.  Anyone
+with a legitimate use for this option likely also possesses the
+knowledge to rig up a suitable analog with minimal effort.  That said,
+the road to removal is long.
+
 ** Option 'erc-warn-about-blank-lines' is more informative.
 Enabled by default, this option now produces more useful feedback
 whenever ERC rejects prompt input containing whitespace-only lines.
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 60cce750355..3a0337eae9a 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -2893,9 +2893,18 @@ I.e. any char in it has the `invisible' property set."
 
 The default is to remove it, since it causes ERC to take up extra
 memory.  If you have code that relies on this property, then set
-this option to nil."
+this option to nil.
+
+Note that this option is deprecated because a value of nil is
+impractical in prolonged sessions with more than a few channels.
+Use `erc-insert-post-hook' or similar and the helper function
+`erc-find-parsed-property' and friends to stash the current
+`erc-response' object as needed.  And instead of using this for
+debugging purposes, try `erc-debug-irc-protocol'."
   :type 'boolean
   :group 'erc)
+(make-obsolete-variable 'erc-remove-parsed-property
+                        "impractical when non-nil" "30.1")
 
 (define-inline erc--assert-input-bounds ()
   (inline-quote
@@ -2972,7 +2981,7 @@ If STRING is nil, the function does nothing."
                   (run-hooks 'erc-insert-post-hook)
                   (when erc-remove-parsed-property
                     (remove-text-properties (point-min) (point-max)
-                                            '(erc-parsed nil))))
+                                            '(erc-parsed nil tags nil))))
                 (erc--refresh-prompt)))))
         (run-hooks 'erc-insert-done-hook)
         (erc-update-undo-list (- (or (marker-position (or erc--insert-marker