Escape backslashes in front-matter

- Handle single-line and multi-line front-matter values for both TOML
  and YAML.

ox-hugo.el

@@ -2368,34 +2368,47 @@ Optional argument FORMAT can be \"toml\" or \"yaml\"."
    ((and prefer-no-quotes
          (string-match-p "\\`[a-zA-Z0-9]+\\'" val))
     val)
-   ((and (org-string-nw-p val)
-         (string-match-p "\n" val))
-    ;; The indentation of the multi-line string is needed only for the
-    ;; YAML format.  But the same is done for TOML too just for better
-    ;; presentation.
-    (setq val (replace-regexp-in-string "^" "  " val))
-
-    (if (and (stringp format)
-             (string= format "yaml"))
-        (progn
-          ;; https://yaml-multiline.info/
-          ;;
-          ;;     |             |foo : >
-          ;;     |abc          |  abc
-          ;;     |       >>>   |
-          ;;     |def          |
-          ;;     |             |  def
-          ;;
-          ;; In Org, a single blank line is used to start a new
-          ;; paragraph. In the YAML multi-line string, that needs to
-          ;; be 2 blank lines.
-          (setq val (replace-regexp-in-string "\n[[:blank:]]*\n" "\n\n\n" val))
-          (format ">\n%s" val))
-      ;; Remove indentation/space from blank lines if any.
-      (setq val (replace-regexp-in-string "\n[[:blank:]]*\n" "\n\n" val))
-      (format "\"\"\"\n%s\n  \"\"\"" val))) ;Triple-quote
+   ((org-string-nw-p val)      ;If `val' is any other non-empty string
+    (cond
+     ((string-match-p "\n" val)       ;Multi-line string
+      ;; The indentation of the multi-line string is needed only for the
+      ;; YAML format.  But the same is done for TOML too just for better
+      ;; presentation.
+      (setq val (replace-regexp-in-string "^" "  " val))
+
+      (if (and (stringp format)
+               (string= format "yaml"))
+          (progn
+            ;; https://yaml-multiline.info/
+            ;;
+            ;;     |             |foo : >
+            ;;     |abc          |  abc
+            ;;     |       >>>   |
+            ;;     |def          |
+            ;;     |             |  def
+            ;;
+            ;; In Org, a single blank line is used to start a new
+            ;; paragraph. In the YAML multi-line string, that needs to
+            ;; be 2 blank lines.
+            (setq val (replace-regexp-in-string "\n[[:blank:]]*\n" "\n\n\n" val))
+            (format ">\n%s" val))
+        ;; Escape the backslashes (only for multi-line TOML).
+        (setq val (replace-regexp-in-string "\\\\" "\\\\\\\\" val))
+
+        ;; Remove indentation/space from blank lines if any.
+        (setq val (replace-regexp-in-string "\n[[:blank:]]*\n" "\n\n" val))
+        (format "\"\"\"\n%s\n  \"\"\"" val))) ;Triple-quote
+     (t                                       ;Single-line string
+      ;; Below 2 replacements are order-dependent.. first escape the
+      ;; backslashes, then escape the quotes with backslashes.
+
+      ;; Escape the backslashes (for both TOML and YAML).
+      (setq val (replace-regexp-in-string "\\\\" "\\\\\\\\" val))
+      ;; Escape the double-quotes.
+      (setq val (replace-regexp-in-string "\"" "\\\\\""  val))
+      (concat "\"" val "\""))))
    (t
-    (concat "\"" (replace-regexp-in-string "\"" "\\\\\""  val) "\""))))
+    "")))
 
 (defun org-hugo--parse-property-arguments (str)
   "Return an alist converted from a string STR of Hugo property value.

test/site/content-org/all-posts.org

@@ -4552,6 +4552,23 @@ If the description is set via the subtree property
 #+begin_description
 Description set in special block
 #+end_description
+***** Single-line description with backslashes (TOML) :escaping:backslashes:front_matter:single_line:
+:PROPERTIES:
+:EXPORT_FILE_NAME: description-single-line-escaping-backslashes-org-special-block-toml
+:END:
+#+begin_description
+Test to check that backslashes in =\|= and =\\= are correctly escaped.
+#+end_description
+Post content.
+***** Multi-line description with backslashes (TOML) :escaping:backslashes:front_matter:multi_line:
+:PROPERTIES:
+:EXPORT_FILE_NAME: description-multi-line-escaping-backslashes-org-special-block-toml
+:END:
+#+begin_description
+Test to check that backslashes in =\|= and =\\= are correctly escaped
+in the front-matter.
+#+end_description
+Post content.
 **** YAML                                                              :yaml:
 :PROPERTIES:
 :EXPORT_HUGO_FRONT_MATTER_FORMAT: yaml
@@ -4575,6 +4592,23 @@ of this post
 *bold* -- /italics/ --- +strikethrough+ =monospace=
 #+end_description
 Post content.
+***** Single-line description with backslashes (YAML) :escaping:backslashes:front_matter:single_line:
+:PROPERTIES:
+:EXPORT_FILE_NAME: description-single-line-escaping-backslashes-org-special-block-yaml
+:END:
+#+begin_description
+Test to check that backslashes in =\|= and =\\= are correctly escaped.
+#+end_description
+Post content.
+***** Multi-line description with backslashes (YAML) :escaping:backslashes:front_matter:multi_line:
+:PROPERTIES:
+:EXPORT_FILE_NAME: description-multi-line-escaping-backslashes-org-special-block-yaml
+:END:
+#+begin_description
+Test to check that backslashes in =\|= and =\\= are correctly escaped
+in the front-matter.
+#+end_description
+Post content.
 ** Locale                                                            :locale:
 :PROPERTIES:
 :EXPORT_HUGO_WITH_LOCALE: t

test/site/content/posts/description-multi-line-escaping-backslashes-org-special-block-toml.md

@@ -0,0 +1,11 @@
++++
+title = "Multi-line description with backslashes (TOML)"
+description = """
+  Test to check that backslashes in `\\|` and `\\\\` are correctly escaped
+  in the front-matter.
+  """
+tags = ["description", "special-block", "toml", "escaping", "backslashes", "front-matter", "multi-line"]
+draft = false
++++
+
+Post content.

test/site/content/posts/description-multi-line-escaping-backslashes-org-special-block-yaml.md

@@ -0,0 +1,10 @@
+---
+title: "Multi-line description with backslashes (YAML)"
+description: >
+  Test to check that backslashes in `\|` and `\\` are correctly escaped
+  in the front-matter.
+tags: ["description", "special-block", "yaml", "escaping", "backslashes", "front-matter", "multi-line"]
+draft: false
+---
+
+Post content.

test/site/content/posts/description-single-line-escaping-backslashes-org-special-block-toml.md

@@ -0,0 +1,8 @@
++++
+title = "Single-line description with backslashes (TOML)"
+description = "Test to check that backslashes in `\\|` and `\\\\` are correctly escaped."
+tags = ["description", "special-block", "toml", "escaping", "backslashes", "front-matter", "single-line"]
+draft = false
++++
+
+Post content.

test/site/content/posts/description-single-line-escaping-backslashes-org-special-block-yaml.md

@@ -0,0 +1,8 @@
+---
+title: "Single-line description with backslashes (YAML)"
+description: "Test to check that backslashes in `\\|` and `\\\\` are correctly escaped."
+tags: ["description", "special-block", "yaml", "escaping", "backslashes", "front-matter", "single-line"]
+draft: false
+---
+
+Post content.