From 6d34dcc9de1f99c795d0a6bcaa416e29c8500eed Mon Sep 17 00:00:00 2001
From: Pengji Zhang <me@pengjiz.com>
Date: Sun, 10 Nov 2024 09:30:01 +0800
Subject: [PATCH] Add option 'elisp-flymake-byte-compile-activate-packages'
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This option controls whether the Flymake Emacs Lisp
byte-compiler should activate user installed packages before
checking the source buffer.  (Bug#65035)

* lisp/progmodes/elisp-mode.el
(elisp-flymake-byte-compile-user-file-p): New predicate function
to check if a buffer is visiting a user file.
(elisp-flymake-byte-compile-activate-packages): New option.
(elisp-flymake--byte-compile-activate-packages): New variable
for caching.
(elisp-flymake-byte-compile): Use the new option.

* etc/NEWS: Announce the new option.

Co-authored-by: João Távora <joaotavora@gmail.com>
---
 etc/NEWS                     |  7 ++++++
 lisp/progmodes/elisp-mode.el | 46 ++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index a6c2c895985..090f4293c8e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -413,6 +413,13 @@ This affects calls to 'warn', 'lwarn', 'display-warning', and
 In most cases, having it enabled leads to a large amount of false
 positives.
 
+---
+*** New user option 'elisp-flymake-byte-compile-activate-packages'.
+This option controls whether or not the Flymake byte-compiler backend
+should activate user installed packages before compiling the source
+buffer.  By default, it is set to activate packages when checking user
+configuration files.  Set it to nil to restore the previous behavior.
+
 ** DocView
 
 ---
diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index 2f931daedc7..3905300c9a8 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -2190,6 +2190,44 @@ elisp-flymake-byte-compile-load-path
 
 (defvar bytecomp--inhibit-lexical-cookie-warning)
 
+(defun elisp-flymake-byte-compile-user-file-p (buffer)
+  "Return non-nil if BUFFER is visiting a user file.
+That means either the file is `user-init-file' or it is in
+`user-emacs-directory'."
+  (when-let* ((file (buffer-local-value 'buffer-file-truename buffer)))
+    (or (and user-emacs-directory
+             (file-in-directory-p file user-emacs-directory))
+        (and user-init-file
+             (string= file (abbreviate-file-name
+                            (file-truename user-init-file)))))))
+
+(defcustom elisp-flymake-byte-compile-activate-packages
+  #'elisp-flymake-byte-compile-user-file-p
+  "Whether to activate packages for Flymake elisp byte-compilation.
+If the value is nil, do not activate installed packages.  If the value
+is a function, it is called with one argument, the source buffer to be
+checked, and installed packages are activated if the function returns
+non-nil.  Otherwise, packages are always activated.
+
+The default value is a predicate function
+`elisp-flymake-byte-compile-user-file-p' (which see), and that means
+packages are activated only for user configuration files.
+
+Note that for efficiency the return value of the predicate function is
+cached the first time it is called.  Type \\[revert-buffer-quick] to
+invalidate the cached value."
+  :type '(choice
+          (const :tag "Don't activate" nil)
+          (const :tag "Always activate" t)
+          (const :tag "Activate for user files"
+                 elisp-flymake-byte-compile-user-file-p)
+          (function :tag "Predicate function"))
+  :group 'lisp
+  :version "31.1")
+
+(defvar-local elisp-flymake--byte-compile-activate-packages :unset
+  "Cached value for `elisp-flymake-byte-compile-activate-packages'.")
+
 ;;;###autoload
 (defun elisp-flymake-byte-compile (report-fn &rest _args)
   "A Flymake backend for elisp byte compilation.
@@ -2205,6 +2243,12 @@ elisp-flymake-byte-compile
     (save-restriction
       (widen)
       (write-region (point-min) (point-max) temp-file nil 'nomessage))
+    (when (eq elisp-flymake--byte-compile-activate-packages :unset)
+      (setq elisp-flymake--byte-compile-activate-packages
+            (if (functionp elisp-flymake-byte-compile-activate-packages)
+                (funcall elisp-flymake-byte-compile-activate-packages
+                         source-buffer)
+              elisp-flymake-byte-compile-activate-packages)))
     (let* ((output-buffer (generate-new-buffer " *elisp-flymake-byte-compile*"))
            ;; Hack: suppress warning about missing lexical cookie in
            ;; *scratch* buffers.
@@ -2223,6 +2267,8 @@ elisp-flymake-byte-compile
                    ;; "--eval" "(setq load-prefer-newer t)" ; for testing
                    ,@(mapcan (lambda (path) (list "-L" path))
                              elisp-flymake-byte-compile-load-path)
+                   ,@(when elisp-flymake--byte-compile-activate-packages
+                       '("-f" "package-activate-all"))
                    ,@warning-suppression-opt
                    "-f" "elisp-flymake--batch-compile-for-flymake"
                    ,temp-file)
-- 
2.47.0