fix(beancount): flymake-bean: false positives from relative paths

Beancount tools and Fava recognize relative paths in include and
document directives, and documents options. However, flymake-bean pipes
the buffer's contents to bean-check via /dev/stdin, so paths are
resolved relative to /dev instead of the location of the containing
beancount file, resulting in file errors. This commit expands those
relatives paths before sending the buffer's contents to bean-check to
resolve these false positives.

modules/lang/beancount/autoload.el

@@ -239,3 +239,62 @@ Return non-nil if successful."
            (concat beancount-timestamped-directive-regexp
                    "\\|" beancount-transaction-regexp)))
       ('search-failed (goto-char pos) nil))))
+
+;;;###autoload
+(defun +beancount--flymake-bean-check--run-a (report-fn &rest _ignored)
+  (unless (executable-find flymake-bean-check-executable)
+    (error "The executable %s doesn't exist. See `flymake-bean-check-executable'"
+           flymake-bean-check-executable))
+  (when (and flymake-bean-check-process
+             (process-live-p flymake-bean-check-process))
+    (kill-process flymake-bean-check-process))
+  (let* ((source (current-buffer))
+         (buffer (generate-new-buffer "*flymake-bean-check*"))
+         (cache-file (flymake-bean-check-cache-filename (buffer-file-name))))
+    (setq flymake-bean-check-process
+          (make-process :buffer buffer
+                        :name "flymake-bean-check"
+                        :noquery t
+                        :connection-type 'pipe
+                        :command (list flymake-bean-check-executable
+                                       "/dev/stdin"
+                                       "--cache-filename" cache-file)
+                        :sentinel
+                        (lambda (proc _event)
+                          (when (memq (process-status proc) '(exit signal))
+                            (unwind-protect
+                                (with-current-buffer buffer
+                                  (goto-char (point-min))
+                                  (let (result)
+                                    (while (re-search-forward flymake-bean-check-location-regexp
+                                                              nil t)
+                                      (pcase-let*
+                                          ((message (match-string 2))
+                                           (`(,begin . ,end) (flymake-diag-region
+                                                              source
+                                                              (string-to-number (match-string 1)))))
+                                        (push (flymake-make-diagnostic source begin end
+                                                                       :error message)
+                                              result)))
+                                    (funcall report-fn (nreverse result))))
+                              (kill-buffer buffer))))))
+    (process-send-string
+     flymake-bean-check-process
+     (save-restriction
+       (widen)
+       (with-temp-buffer
+         (save-excursion (insert-buffer-substring source))
+         (while (re-search-forward (rx bol
+                                       (or (seq (= 4 num) "-" (= 2 num) "-" (= 2 num) (+ " ")
+                                                "document" (+ " ")
+                                                (+ (or alnum ":" "_" "-")))
+                                           "include"
+                                           (seq "option" (+ " ") "\"documents\""))
+                                       (+ " ") "\""
+                                       (group (+ (not "\""))))
+                                   nil t)
+           (replace-match (expand-file-name
+                           (match-string-no-properties 1))
+                          t t nil 1))
+         (buffer-substring-no-properties (point-min) (point-max)))))
+    (process-send-eof flymake-bean-check-process)))

modules/lang/beancount/config.el

@@ -26,9 +26,12 @@
     :around #'beancount--fava-filter
     (funcall fn process (ansi-color-filter-apply output)))
 
-  (defadvice! +beancount--widen-before-flymake-bean-check--run-a (fn &rest args)
+  ;; HACK: Widens the buffer so flymake never operates on partial buffer
-    :around #'flymake-bean-check--run
+  ;;   contents. Also replaces any relative file paths in include and document
-    (save-restriction (widen) (apply fn args)))
+  ;;   directives with an absolute path, so bean-check doesn't throw false
+  ;;   positives due to flymake-bean's implementation.
+  (advice-add #'flymake-bean-check--run :override #'+beancount--flymake-bean-check--run-a)
+
 
   (map! :map beancount-mode-map
         :m "[[" #'+beancount/previous-transaction