Improve error handling and callback execution

[benthamite]

Description

This PR fixes an issue where the error (wrong-type-argument sequencep <number>) is triggered when LanguageTool returns an error response. The problem occurs because the current implementation calls the error callback but then continues execution, attempting to apply mapcar to a non-sequence value.

Changes

• Restructured the flycheck-languagetool--read-results function to use an if-else pattern
• Ensured that after reporting an error via the callback, the function terminates without further processing
• Moved the error handling to properly encapsulate the entire callback execution

[jcs090218]

The error function call should stop the execution. 🤔

[benthamite]

Mmh, I'm not sure what’s going on. The errors disappeared after what I believe was this change, but I also made other changes. Another candidate is

-    (with-current-buffer source-buffer
-      (funcall
-       callback 'finished
-       (flycheck-increment-error-columns
-        (mapcar
-         (lambda (x)
-           (apply #'flycheck-error-new-at `(,@x :checker languagetool)))
-         (condition-case err
-             (flycheck-languagetool--check-all results)
-           (error (funcall callback 'errored (error-message-string err))))))))))
+    ;; Check if the source buffer is still live before processing results.
+    (when (buffer-live-p source-buffer)
+      (with-current-buffer source-buffer
+        (funcall
+         callback 'finished
+         (flycheck-increment-error-columns
+          (mapcar
+           (lambda (x)
+             (apply #'flycheck-error-new-at `(,@x :checker languagetool)))
+           (condition-case err
+               (flycheck-languagetool--check-all results)

Do you think this might be the right way to patch it?

The backtrace is:

Debugger entered--Lisp error: (error "Selecting deleted buffer")
  flycheck-languagetool--read-results(nil #<killed buffer> #f(compiled-function (&rest args) #<bytecode 0x3b3e1e5358fd5da>))
  url-http-activate-callback()
  url-http-content-length-after-change-function(4194444 4829059 634615)