Support custom front-matter with nested maps (TOML tables)

The syntax for specifying nested map values custom front-matter is:

Using property drawer (in subtrees):

    :EXPORT_HUGO_CUSTOM_FRONT_MATTER: :PARENT_KEY{} '((KEY1 . VAL1) (KEY2 . VAL2) (KEY3 . VAL3) ..)

Using keyword:

    #+hugo_custom_front_matter: :PARENT_KEY{} '((KEY1 . VAL1) (KEY2 . VAL2) (KEY3 . VAL3) ..)

The "{}" at the end of the key name is what tells ox-hugo that this is
a nested map.

Only 1 level of nested keys is supported.

Fixes https://github.com/kaushalmodi/ox-hugo/issues/139.

ox-hugo.el

@@ -2779,6 +2779,7 @@ are \"toml\" and \"yaml\"."
         (front-matter "")
         (indent (make-string 2 ? ))
         (bf-string "")
+        (custom-nested-string "")
         (menu-string "")
         (res-string ""))
     ;; (message "hugo fm format: %s" format)
@@ -2802,6 +2803,55 @@ are \"toml\" and \"yaml\"."
           ;; and then append it to `front-matter' at the end.  Do the
           ;; same for blackfriday param values.
           (cond
+           ;; :EXPORT_HUGO_CUSTOM_FRONT_MATTER: :dog{} '((legs . 4) ("eyes" . 2) (friends . (poo boo)))
+           ((string-suffix-p "{}" key) ;custom front-matter with nested map value
+            (let* ((custom-nested-alist value)
+                   ;; Menu entry string might need to be quoted if
+                   ;; it contains spaces, for example.
+                   (custom-nested-parent-key (org-string-nw-p (replace-regexp-in-string "{}\\'" "" key)))
+                   (custom-nested-parent-key-str "")
+                   (custom-nested-keyval-str ""))
+              ;; (message "[nested entry DBG] = %s" custom-nested-parent-key)
+              ;; (message "[nested alist DBG] = %S" custom-nested-alist)
+              (when custom-nested-parent-key
+                (setq custom-nested-parent-key-str (cond ((string= format "toml")
+                                                          (format "[%s]\n" custom-nested-parent-key))
+                                                         ((string= format "yaml")
+                                                          (format "%s%s\n" custom-nested-parent-key sign))
+                                                         (t
+                                                          "")))
+                (dolist (custom-nested-pair custom-nested-alist)
+                  (unless (consp custom-nested-pair)
+                    (user-error "ox-hugo: Custom front-matter values with nested maps need to be an alist of conses"))
+                  ;; (message "[nested pair DBG] = %S" custom-nested-pair)
+                  (let* ((custom-nested-key (car custom-nested-pair))
+                         (custom-nested-key (cond
+                                             ((symbolp custom-nested-key)
+                                              (symbol-name custom-nested-key))
+                                             (t
+                                              custom-nested-key)))
+                         (custom-nested-value (cdr custom-nested-pair))
+                         (custom-nested-value (cond
+                                               ((and custom-nested-value
+                                                     (listp custom-nested-value))
+                                                (org-hugo--get-yaml-toml-list-string custom-nested-value))
+                                               ((null custom-nested-value)
+                                                "false")
+                                               ((equal custom-nested-value 't)
+                                                "true")
+                                               (t
+                                                (org-hugo--quote-string custom-nested-value)))))
+                    ;; (message "nested DBG: %S KEY %S->%S VALUE %S->%S" custom-nested-parent-key
+                    ;;          (car custom-nested-pair) custom-nested-key
+                    ;;          (cdr custom-nested-pair) custom-nested-value)
+                    (when custom-nested-value
+                      (setq custom-nested-keyval-str
+                            (concat custom-nested-keyval-str
+                                    (format "%s%s%s %s\n"
+                                            indent custom-nested-key sign custom-nested-value))))))
+                (when (org-string-nw-p custom-nested-keyval-str)
+                  (setq custom-nested-string (concat custom-nested-string custom-nested-parent-key-str
+                                                     custom-nested-keyval-str))))))
            ((string= key "menu")
             ;; Menu name needs to be non-nil to insert menu info in front matter.
             (when (assoc 'menu value)
@@ -2955,7 +3005,7 @@ are \"toml\" and \"yaml\"."
                                          (org-hugo--get-yaml-toml-list-string value))
                                         (t
                                          (org-hugo--quote-string value nil format)))))))))))
-    (concat sep front-matter bf-string menu-string res-string sep)))
+    (concat sep front-matter bf-string custom-nested-string menu-string res-string sep)))
 
 (defun org-hugo--selective-property-inheritance ()
   "Return a list of properties that should be inherited."

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

@@ -1689,6 +1689,33 @@ The following results in the 'genres' property having the value
 :EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :booleans '(true false)
 :END:
 {{{oxhugoissue(99)}}}
+** Custom front matter with table values or nested maps :TOML_table:nested_map:
+*** Custom front matter with nested maps in TOML
+:PROPERTIES:
+:EXPORT_FILE_NAME: custom-front-matter-with-nested-maps-toml
+:EXPORT_HUGO_FRONT_MATTER_FORMAT: toml
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER: :dog{} '((legs . 4) ("eyes" . 2) (friends . (poo boo)))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :header{} '((image . "projects/Readingabook.jpg") (caption . "stay hungry, stay foolish"))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :collection{} '((nothing) (nonnil . t) (animals . (dog cat "penguin" "mountain gorilla")) (strings-symbols . ("abc" def "two words")) (integers . (123 -5 17 1_234)) (floats . (12.3 -5.0 -17E-6)) (booleans . (true false)))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :empty_parent_key{}
+:END:
+#+begin_description
+Custom TOML front-matter with TOML tables.
+#+end_description
+{{{oxhugoissue(139)}}}
+*** Custom front matter with nested maps in YAML
+:PROPERTIES:
+:EXPORT_FILE_NAME: custom-front-matter-with-nested-maps-yaml
+:EXPORT_HUGO_FRONT_MATTER_FORMAT: yaml
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER: :dog{} '((legs . 4) ("eyes" . 2) (friends . (poo boo)))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :header{} '((image . "projects/Readingabook.jpg") (caption . "stay hungry, stay foolish"))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :collection{} '((nothing) (nonnil . t) (animals . (dog cat "penguin" "mountain gorilla")) (strings-symbols . ("abc" def "two words")) (integers . (123 -5 17 1_234)) (floats . (12.3 -5.0 -17E-6)) (booleans . (true false)))
+:EXPORT_HUGO_CUSTOM_FRONT_MATTER+: :empty_parent_key{}
+:END:
+#+begin_description
+Custom YAML front-matter with nested maps.
+#+end_description
+{{{oxhugoissue(139)}}}
 * Resources                                                       :resources:
 ** TOML                                                                :toml:
 *** Post with resources in front-matter (TOML)

test/site/content-org/keyword-collection.org

@@ -38,6 +38,12 @@
 #+hugo_custom_front_matter: :floats '(12.3 -5.0 -17E-6)
 #+hugo_custom_front_matter: :booleans '(true false)
 
+# Custom front-matter with nested maps
+#+hugo_custom_front_matter: :dog{} '((legs . 4) ("eyes" . 2) (friends . (poo boo)))
+#+hugo_custom_front_matter: :header{} '((image . "projects/Readingabook.jpg") (caption . "stay hungry, stay foolish"))
+#+hugo_custom_front_matter: :collection{} '((nothing) (nonnil . t) (animals . (dog cat "penguin" "mountain gorilla")) (strings-symbols . ("abc" def "two words")) (integers . (123 -5 17 1_234)) (floats . (12.3 -5.0 -17E-6)) (booleans . (true false)))
+#+hugo_custom_front_matter: :empty_parent_key{}
+
 # Blackfriday
 #+hugo_blackfriday: :smartdashes :fractions nil :plainidanchors false
 #+hugo_blackfriday: :angledquotes t :hrefTargetBlank true
@@ -87,6 +93,8 @@
 This is a test post that tests that keywords set across multiple Org
 keywords get collected.
 
+#+hugo: more
+
 * Keyword Collection Tested to work [15/15]
 - [X] =#+author=
 - [X] =#+hugo_tags=

test/site/content/posts/custom-front-matter-with-nested-maps-toml.md

@@ -0,0 +1,23 @@
++++
+title = "Custom front matter with nested maps in TOML"
+description = "Custom TOML front-matter with TOML tables."
+tags = ["custom-fm", "TOML-Table", "nested-map"]
+draft = false
+[dog]
+  legs = 4
+  eyes = 2
+  friends = ["poo", "boo"]
+[header]
+  image = "projects/Readingabook.jpg"
+  caption = "stay hungry, stay foolish"
+[collection]
+  nothing = false
+  nonnil = true
+  animals = ["dog", "cat", "penguin", "mountain gorilla"]
+  strings-symbols = ["abc", "def", "two words"]
+  integers = [123, -5, 17, 1_234]
+  floats = [12.3, -5.0, -1.7e-05]
+  booleans = [true, false]
++++
+
+`ox-hugo` Issue #[139](https://github.com/kaushalmodi/ox-hugo/issues/139)

test/site/content/posts/custom-front-matter-with-nested-maps-yaml.md

@@ -0,0 +1,23 @@
+---
+title: "Custom front matter with nested maps in YAML"
+description: "Custom YAML front-matter with nested maps."
+tags: ["custom-fm", "TOML-Table", "nested-map"]
+draft: false
+dog:
+  legs: 4
+  eyes: 2
+  friends: ["poo", "boo"]
+header:
+  image: "projects/Readingabook.jpg"
+  caption: "stay hungry, stay foolish"
+collection:
+  nothing: false
+  nonnil: true
+  animals: ["dog", "cat", "penguin", "mountain gorilla"]
+  strings-symbols: ["abc", "def", "two words"]
+  integers: [123, -5, 17, 1_234]
+  floats: [12.3, -5.0, -1.7e-05]
+  booleans: [true, false]
+---
+
+`ox-hugo` Issue #[139](https://github.com/kaushalmodi/ox-hugo/issues/139)

test/site/content/posts/keyword-collection.md

@@ -28,6 +28,21 @@ booleans = [true, false]
   smartDashes = false
   fractions = false
   angledQuotes = true
+[dog]
+  legs = 4
+  eyes = 2
+  friends = ["poo", "boo"]
+[header]
+  image = "projects/Readingabook.jpg"
+  caption = "stay hungry, stay foolish"
+[collection]
+  nothing = false
+  nonnil = true
+  animals = ["dog", "cat", "penguin", "mountain gorilla"]
+  strings-symbols = ["abc", "def", "two words"]
+  integers = [123, -5, 17, 1_234]
+  floats = [12.3, -5.0, -1.7e-05]
+  booleans = [true, false]
 [menu.foo]
   identifier = "keyword-collection"
   weight = 10
@@ -54,6 +69,8 @@ booleans = [true, false]
 This is a test post that tests that keywords set across multiple Org
 keywords get collected.
 
+<!--more-->
+
 
 ## Keyword Collection Tested to work <code>[15/15]</code> {#keyword-collection-tested-to-work}