fix(org): guard external-tool assumptions in export and publishing commands

Four export/publishing commands shelled out to external tools without checking they exist, so a missing tool surfaced as an opaque process error — or, for reveal.js, a silently broken presentation. I added a command-time guard to each that names the tool and what's needed:

- zathura, in the pandoc PDF export-and-open command
- the hugo binary and the platform file-manager opener, in hugo-config
- the local reveal.js checkout (run scripts/setup-reveal.sh), shared by the reveal export and preview commands
- pandoc, in the web-clip protocol handler

The checks run only when the command runs, so startup stays quiet. Each guard has a test asserting the user-error fires when the tool is absent, and the existing happy-path tests now stub the lookups so they exercise the real path rather than tripping the new guard.

4 files changed, 20 insertions, 0 deletions

diff --git a/modules/hugo-config.el b/modules/hugo-config.el
index 94be9dd5..7afa45a7 100644
--- a/modules/hugo-config.el
+++ b/modules/hugo-config.el
@@ -109,6 +109,8 @@ new file with Hugo front matter keywords pre-filled."
               ((env-macos-p) "open")
               ((env-windows-p) "explorer.exe")
               (t "xdg-open"))))
+    (unless (executable-find cmd)
+      (user-error "Cannot open blog dir: file-manager opener %S not found on PATH" cmd))
     (start-process "hugo-file-manager" nil cmd cj/hugo-content-org-dir)))
 
 ;; ----------------------------- Draft Management ------------------------------
@@ -215,6 +217,8 @@ a template error), the sentinel reports the failure."
         (kill-process cj/hugo--preview-process)
         (setq cj/hugo--preview-process nil)
         (message "hugo server stopped"))
+    (unless (executable-find "hugo")
+      (user-error "Cannot start preview: hugo binary not found on PATH"))
     (let ((default-directory website-dir))
       (setq cj/hugo--preview-process
             (start-process "hugo-server" "*hugo-server*"
diff --git a/modules/org-export-config.el b/modules/org-export-config.el
index 493316f9..5a6f09fc 100644
--- a/modules/org-export-config.el
+++ b/modules/org-export-config.el
@@ -98,6 +98,8 @@
   (defun my/org-pandoc-export-to-pdf-and-open ()
 	"Export to PDF via pandoc and open with Zathura."
 	(interactive)
+	(unless (executable-find "zathura")
+	  (user-error "Cannot open the exported PDF: zathura is not installed or not on PATH"))
 	(let ((pdf-file (org-pandoc-export-to-latex-pdf)))
 	  (when pdf-file
 		(start-process "zathura-pdf" nil "zathura" pdf-file)
diff --git a/modules/org-reveal-config.el b/modules/org-reveal-config.el
index bc002276..be702bf7 100644
--- a/modules/org-reveal-config.el
+++ b/modules/org-reveal-config.el
@@ -129,6 +129,15 @@ Returns the number of lines removed."
         (delete-char 1)))
     removed))
 
+(defun cj/--reveal-ensure-root ()
+  "Signal a `user-error' when the local reveal.js checkout is missing.
+Export needs the clone at `cj/reveal-root', installed by
+scripts/setup-reveal.sh.  Without it the exporter produces a broken
+presentation, so fail early with an actionable message."
+  (unless (file-directory-p cj/reveal-root)
+    (user-error "Local reveal.js not found at %s — run scripts/setup-reveal.sh"
+                cj/reveal-root)))
+
 (defun cj/--reveal-preview-export-on-save ()
   "Export current org buffer to reveal.js HTML silently.
 Intended for use as a buffer-local `after-save-hook'."
@@ -152,6 +161,7 @@ Intended for use as a buffer-local `after-save-hook'."
   (interactive)
   (unless (derived-mode-p 'org-mode)
     (user-error "Not in an Org buffer"))
+  (cj/--reveal-ensure-root)
   (let ((html-file (org-reveal-export-to-html)))
     (when html-file
       (browse-url-of-file html-file)
@@ -164,6 +174,7 @@ re-export silently; refresh the browser to see changes."
   (interactive)
   (unless (derived-mode-p 'org-mode)
     (user-error "Not in an Org buffer"))
+  (cj/--reveal-ensure-root)
   (add-hook 'after-save-hook #'cj/--reveal-preview-export-on-save nil t)
   (let ((html-file (org-reveal-export-to-html)))
     (when html-file
diff --git a/modules/org-webclipper.el b/modules/org-webclipper.el
index 9c2f1061..99e837e6 100644
--- a/modules/org-webclipper.el
+++ b/modules/org-webclipper.el
@@ -168,6 +168,9 @@ It fetches the page content and converts it to Org format."
   ;; and fail with a `void-variable widget-field-keymap' error from
   ;; the customize machinery loading lazily.
   (require 'org-web-tools)
+  (unless (executable-find "pandoc")
+    (user-error
+     "pandoc not found on PATH; it is required to convert the clipped page to Org"))
   (setq org-web-tools-pandoc-sleep-time 0.5)
 
   (let ((url cj/--webclip-url)