Add tags hierarchy support

ox-hugo.el

@@ -3537,6 +3537,56 @@ INFO is a plist used as a communication channel."
     ;; (message "[fm tags DBG] %S" tags)
     ;; (message "[fm categories DBG] %S" categories)
     ;; (message "[fm keywords DBG] %S" keywords)
+
+    ;; Append group tags to user-set tags if tag groups are defined in
+    ;; the buffer.
+    (when (and org-group-tags org-tag-groups-alist)
+      (let (tag-groups-alist-mod)
+
+        ;; Copy `org-tag-groups-alist' to `tag-groups-alist-mod' while
+        ;; modifying the tags and categories as defined by
+        ;; `org-hugo-tag-processing-functions'.
+        (dolist (group org-tag-groups-alist)
+          (let ((group-mod group))
+            (dolist (fn org-hugo-tag-processing-functions group-mod)
+              (setq group-mod (funcall fn group-mod info)))
+            (push group-mod tag-groups-alist-mod)))
+
+        (dolist (t-or-c (append tags categories))
+          (let ((to-be-searched `(,t-or-c)))
+            (while (> (length to-be-searched) 0)
+              ;; (message "[tag group DBG] t and c to search: %S" to-be-searched)
+              (let ((tc (pop to-be-searched)))
+                (dolist (group tag-groups-alist-mod)
+                  ;; (message "[tag group DBG]   Searching %s in %S" tc group)
+                  (when (member tc group)
+                    (let ((head-tag (car group)))
+                      (if (org-hugo--category-p head-tag)
+                          (let ((head-cat (replace-regexp-in-string "\\`@" "" head-tag)))
+                            (unless (member head-cat categories)
+                              (push head-cat categories)
+                              ;; (message "[tag group DBG] .... Adding cat %s" head-cat)
+                              ))
+                        (unless (member head-tag tags)
+                          (push head-tag tags)
+                          ;; (message "[tag group DBG] .... Adding tag %s" head-tag)
+                          ))
+                      ;; Add the current `head-tag' as the new tag to
+                      ;; search if current tag or category (`tc') is not
+                      ;; the `head-tag', and if it's not already in the
+                      ;; search list.
+                      (unless (or (string= tc head-tag)
+                                  (member head-tag to-be-searched))
+                        (push head-tag to-be-searched))))))))))
+      ;; (message "[tag group DBG] updated tags: %S" tags)
+      ;; (message "[tag group DBG] updated categories: %S" categories)
+
+      ;; Overwrite the 'tags and 'categories key values in `data' with
+      ;; the updated values.
+      ;; https://stackoverflow.com/a/40815365/1219634
+      (setf (alist-get 'tags data) tags)
+      (setf (alist-get 'categories data) categories))
+
     (setq data (org-hugo--replace-keys-maybe data info))
     (setq ret (org-hugo--gen-front-matter data fm-format))
     (if (and (string= "toml" fm-format)

test/site/content-org/tag-hierarchy.org

@@ -0,0 +1,67 @@
+#+hugo_base_dir: ../
+
+#+seq_todo: TODO DRAFT DONE
+
+#+property: header-args :eval never-export
+
+#+startup: indent
+
+#+macro: doc [[https://ox-hugo.scripter.co/doc/$1][$2]]
+#+macro: oxhugoissue =ox-hugo= Issue #[[https://github.com/kaushalmodi/ox-hugo/issues/$1][$1]]
+
+#+author:
+
+#+tags: [ @GTD : Control Persp ]
+#+tags: [ Control : Context Task ]
+#+tags: [ Persp : Vision Goal AOF Project ]
+
+#+tags: [ @food : @fruit @vegetable @has__seeds ]
+#+tags: [ @fruit : apple banana ]
+#+tags: [ apple : pink_lady granny_smith ]
+#+tags: [ @vegetable : potato squash ]
+#+tags: [ @has__seeds : apple squash ]
+
+#+filetags: tag-groups tag-hierarchy
+
+* Body
+{{{oxhugoissue(341)}}}
+
+https://orgmode.org/manual/Tag-Hierarchy.html
+* Tag Hierarchy: Basic                                               :Vision:
+:PROPERTIES:
+:EXPORT_FILE_NAME: tag-hierarchy-basic
+:END:
+#+begin_description
+Test the example tag groups from
+https://orgmode.org/manual/Tag-Hierarchy.html.
+#+end_description
+#+include: "./tag-hierarchy.org::*Body" :only-contents t
+* Tag Hierarchy: Multiple Tags from Groups         :Vision:AOF:Persp:Context:
+:PROPERTIES:
+:EXPORT_FILE_NAME: tag-hierarchy-multiple-tags
+:END:
+#+begin_description
+Test multiple tags from tag groups -- including adding tags which are
+already group tags of some other tags.
+#+end_description
+#+include: "./tag-hierarchy.org::*Body" :only-contents t
+
+Here, ~Persp~ tag is added manually, but it is also the group head for
+~Vision~ and ~AOF~ tags.
+* Tag Hierarchy: Tags with Multiple Groups                           :squash:
+:PROPERTIES:
+:EXPORT_FILE_NAME: tag-hierarchy-tags-with-multiple-group-heads
+:END:
+#+begin_description
+Test tags which belong in multiple groups and so they have multiple
+group head tags.
+#+end_description
+#+include: "./tag-hierarchy.org::*Body" :only-contents t
+* Tag Hierarchy: Tags with hyphens and spaces                     :pink_lady:
+:PROPERTIES:
+:EXPORT_FILE_NAME: tag-hierarchy-tags-with-hyphens-and-spaces
+:END:
+#+begin_description
+Test tags containing hyphens and spaces
+#+end_description
+#+include: "./tag-hierarchy.org::*Body" :only-contents t

test/site/content/posts/tag-hierarchy-basic.md

@@ -0,0 +1,14 @@
++++
+title = "Tag Hierarchy: Basic"
+description = """
+  Test the example tag groups from
+  <https://orgmode.org/manual/Tag-Hierarchy.html>.
+  """
+tags = ["Persp", "tag-groups", "tag-hierarchy", "Vision"]
+categories = ["GTD"]
+draft = false
++++
+
+`ox-hugo` Issue #[341](https://github.com/kaushalmodi/ox-hugo/issues/341)
+
+<https://orgmode.org/manual/Tag-Hierarchy.html>

test/site/content/posts/tag-hierarchy-multiple-tags.md

@@ -0,0 +1,17 @@
++++
+title = "Tag Hierarchy: Multiple Tags from Groups"
+description = """
+  Test multiple tags from tag groups -- including adding tags which are
+  already group tags of some other tags.
+  """
+tags = ["Control", "tag-groups", "tag-hierarchy", "Vision", "AOF", "Persp", "Context"]
+categories = ["GTD"]
+draft = false
++++
+
+`ox-hugo` Issue #[341](https://github.com/kaushalmodi/ox-hugo/issues/341)
+
+<https://orgmode.org/manual/Tag-Hierarchy.html>
+
+Here, `Persp` tag is added manually, but it is also the group head for
+`Vision` and `AOF` tags.

test/site/content/posts/tag-hierarchy-tags-with-hyphens-and-spaces.md

@@ -0,0 +1,11 @@
++++
+title = "Tag Hierarchy: Tags with hyphens and spaces"
+description = "Test tags containing hyphens and spaces"
+tags = ["apple", "tag-groups", "tag-hierarchy", "pink-lady"]
+categories = ["food", "fruit", "has seeds"]
+draft = false
++++
+
+`ox-hugo` Issue #[341](https://github.com/kaushalmodi/ox-hugo/issues/341)
+
+<https://orgmode.org/manual/Tag-Hierarchy.html>

test/site/content/posts/tag-hierarchy-tags-with-multiple-group-heads.md

@@ -0,0 +1,14 @@
++++
+title = "Tag Hierarchy: Tags with Multiple Groups"
+description = """
+  Test tags which belong in multiple groups and so they have multiple
+  group head tags.
+  """
+tags = ["tag-groups", "tag-hierarchy", "squash"]
+categories = ["food", "vegetable", "has seeds"]
+draft = false
++++
+
+`ox-hugo` Issue #[341](https://github.com/kaushalmodi/ox-hugo/issues/341)
+
+<https://orgmode.org/manual/Tag-Hierarchy.html>