[elpa] externals/xref-union 0d585d722e 2/5: Fix construction of union backends

[ELPA Syncer]

branch: externals/xref-union
commit 0d585d722e7b5ea57f379979337604bda69191e3
Author: Philip Kaludercic <philip.kaludercic@fau.de>
Commit: Philip Kaludercic <philip.kaludercic@fau.de>

    Fix construction of union backends
    
    We cannot just directly use xref-backend-functions, since a hook is
    not just a list of functions that are to executed.  Quoting from
    (elisp) Running Hooks,
    
         If the hook variable is buffer-local, the buffer-local variable
         will be used instead of the global variable.  However, if the
         buffer-local variable contains the element ‘t’, the global hook
         variable will be run as well.
    
    Hence we need to collect all the functions that we want to add to the
    union backend, in this case by using `run-hook-wrapped' and storing
    the backends the hook generates.
---
 xref-union.el | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/xref-union.el b/xref-union.el
index 8bb486b28e..a8246672ad 100644
--- a/xref-union.el
+++ b/xref-union.el
@@ -106,12 +106,18 @@ PATTERN is specified in `xref-backend-apropos'."
   (when xref-union--current
     (remove-hook 'xref-backend-functions xref-union--current))
   (when xref-union-mode
-    (thread-last
-      xref-union-excluded-backends
-      (seq-difference xref-backend-functions)
-      (cons 'union)
-      (setq xref-union--current)
-      (add-hook 'xref-backend-functions))))
+    (let (backends)
+      ;; Collect all (local and global) functions in
+      ;; `xref-backend-functions' into a local list.
+      (run-hook-wrapped
+       'xref-backend-functions
+       (lambda (b)
+         (setq b (funcall b))
+         (unless (and b (member b xref-union-excluded-backends))
+           (push b backends))
+         nil))
+      (setq xref-union--current (cons 'union backends))
+      (add-hook 'xref-backend-functions xref-union--current))))
 
 ;; LocalWords: backend backends