ox: Simplify syntax for attributes

* lisp/ox.el (org-export-read-attribute): Do not use `read' to read
  attributes.  Instead, extract keywords and values from it, which
  means each value will be a string when non-nil.
* contrib/lisp/ox-groff.el (org-groff-link--inline-image): Use new
  attribute syntax.  Small refactoring.
* lisp/ox-ascii.el (org-ascii-horizontal-rule): Use new attribute
  syntax.
* lisp/ox-beamer.el (org-beamer-plain-list): Use new attribute syntax.
* lisp/ox-html.el (org-html--textarea-block): Use new attribute
  syntax.
* lisp/ox-latex.el (org-latex--inline-image, org-latex--org-table,
  org-latex--math-table): Use new attribute syntax.
* lisp/ox-man.el (org-man-table--org-table): Use new attribute syntax.
  Small refactoring.
* lisp/ox-odt.el (org-odt-link--inline-image, org-odt-table-cell): Use
  new attribute syntax.
* testing/lisp/test-ox.el: Add tests.

This patch introduces two changes.  To begin with, it removes the need
for quoting and escaping characters.  Also, all non-nil values are
stored as strings.  As an exception "nil" is stored as nil.

9 files changed, 108 insertions, 96 deletions

diff --git a/contrib/lisp/ox-groff.el b/contrib/lisp/ox-groff.el
index ab308f3..b22ef11 100644
--- a/contrib/lisp/ox-groff.el
+++ b/contrib/lisp/ox-groff.el
@@ -1211,11 +1211,11 @@ used as a communication channel."
                    (expand-file-name raw-path))))
          (attr (org-export-read-attribute :attr_groff link))
          (placement
-          (case (plist-get attr :position)
-            ('center "")
-            ('left "-L")
-            ('right "-R")
-            (t "")))
+          (let ((pos (plist-get attr :position)))
+	    (cond ((string= pos 'center) "")
+		  ((string= pos 'left) "-L")
+		  ((string= pos 'right) "-R")
+		  (t ""))))
 	 (width  (or (plist-get attr :width) ""))
 	 (height (or (plist-get attr :height) ""))
 	 (caption (and (not (plist-get attr :disable-caption))
@@ -1225,7 +1225,7 @@ used as a communication channel."
     (concat
      (cond
       ((and org-groff-raster-to-ps
-            (or  (string-match ".\.png$" path) 
+            (or  (string-match ".\.png$" path)
                  (string-match ".\.jpg$" path)))
        (let ((eps-path (concat path ".eps")))
          (shell-command (format org-groff-raster-to-ps path eps-path))
@@ -1660,37 +1660,20 @@ This function assumes TABLE has `org' as its `:type' attribute."
          (lines (org-split-string contents "\n"))
 
          (attr-list
-          (let (result-list)
-            (dolist (attr-item
-                     (list
-                      (if (plist-get attr :expand)
-                          "expand" nil)
-
-                      (case (plist-get attr :placement)
-                        ('center "center")
-                        ('left nil)
-                        (t
-                         (if org-groff-tables-centered
-                             "center" "")))
-
-                      (case (plist-get attr :boxtype)
-                        ('box "box")
-                        ('doublebox "doublebox")
-                        ('allbox "allbox")
-                        ('none nil)
-                        (t "box"))))
-
-              (if (not (null attr-item))
-                  (add-to-list 'result-list attr-item)))
-            result-list))
+	  (delq nil
+		(list (and (plist-get attr :expand) "expand")
+		      (let ((placement (plist-get attr :placement)))
+			(cond ((string= placement 'center) "center")
+			      ((string= placement 'left) nil)
+			      (t (if org-groff-tables-centered "center" ""))))
+		      (or (plist-get attr :boxtype) "box"))))
 
          (title-line  (plist-get attr :title-line))
          (long-cells (plist-get attr :long-cells))
 
          (table-format
           (concat
-           (format "%s"
-                   (or (car attr-list) ""))
+           (or (car attr-list) "")
            (or
             (let (output-list)
 	      (when (cdr attr-list)
diff --git a/lisp/ox-ascii.el b/lisp/ox-ascii.el
index 76da33a..6eb96b3 100644
--- a/lisp/ox-ascii.el
+++ b/lisp/ox-ascii.el
@@ -1218,7 +1218,9 @@ information."
 	(spec-width
 	 (org-export-read-attribute :attr_ascii horizontal-rule :width)))
     (org-ascii--justify-string
-     (make-string (if (wholenump spec-width) spec-width text-width)
+     (make-string (if (and spec-width (string-match "^[0-9]+$" spec-width))
+		      (string-to-number spec-width)
+		    text-width)
 		  (if (eq (plist-get info :ascii-charset) 'utf-8) ?― ?-))
      text-width 'center)))
 
diff --git a/lisp/ox-beamer.el b/lisp/ox-beamer.el
index 282da7c..f0f5ef0 100644
--- a/lisp/ox-beamer.el
+++ b/lisp/ox-beamer.el
@@ -783,7 +783,7 @@ contextual information."
 		      (org-export-read-attribute :attr_latex plain-list)
 		      (org-export-read-attribute :attr_beamer plain-list)))
 	 (latex-type (let ((env (plist-get attributes :environment)))
-		       (cond (env (format "%s" env))
+		       (cond (env)
 			     ((eq type 'ordered) "enumerate")
 			     ((eq type 'descriptive) "description")
 			     (t "itemize")))))
@@ -793,11 +793,11 @@ contextual information."
 	     latex-type
 	     ;; Default overlay specification, if any.
 	     (org-beamer--normalize-argument
-	      (format "%s" (or (plist-get attributes :overlay) ""))
+	      (or (plist-get attributes :overlay) "")
 	      'defaction)
 	     ;; Second optional argument depends on the list type.
 	     (org-beamer--normalize-argument
-	      (format "%s" (or (plist-get attributes :options) ""))
+	      (or (plist-get attributes :options) "")
 	      'option)
 	     ;; Eventually insert contents and close environment.
 	     contents
diff --git a/lisp/ox-html.el b/lisp/ox-html.el
index c0e2205..c55be12 100644
--- a/lisp/ox-html.el
+++ b/lisp/ox-html.el
@@ -1214,9 +1214,9 @@ When STANDALONE-P is t, wrap the <img.../> into a <div>...</div>."
 (defun org-html--textarea-block (element)
   "Transcode ELEMENT into a textarea block.
 ELEMENT is either a src block or an example block."
-  (let ((code (car (org-export-unravel-code element)))
-	(attr (org-export-read-attribute :attr_html element)))
-    (format "<p>\n<textarea cols=\"%d\" rows=\"%d\">\n%s</textarea>\n</p>"
+  (let* ((code (car (org-export-unravel-code element)))
+	 (attr (org-export-read-attribute :attr_html element)))
+    (format "<p>\n<textarea cols=\"%s\" rows=\"%s\">\n%s</textarea>\n</p>"
 	    (or (plist-get attr :width) 80)
 	    (or (plist-get attr :height) (org-count-lines code))
 	    code)))
diff --git a/lisp/ox-latex.el b/lisp/ox-latex.el
index 3d3fc3a..fa66bb4 100644
--- a/lisp/ox-latex.el
+++ b/lisp/ox-latex.el
@@ -1814,17 +1814,17 @@ used as a communication channel."
 	 (comment-include (if (plist-get attr :comment-include) "%" ""))
 	 ;; It is possible to specify width and height in the
 	 ;; ATTR_LATEX line, and also via default variables.
-	 (width (format "%s" (cond ((plist-get attr :width))
-				   ((plist-get attr :height) "")
-				   ((eq float 'figure) "0.7\\textwidth")
-				   ((eq float 'wrap) "0.48\\textwidth")
-				   (t org-latex-image-default-width))))
-	 (height (format "%s" (cond ((plist-get attr :height))
-				    ((or (plist-get attr :width)
-					 (memq float '(figure wrap))) "")
-				    (t org-latex-image-default-height))))
-	 (options (let ((opt (format "%s" (or (plist-get attr :options)
-					      org-latex-image-default-option))))
+	 (width (cond ((plist-get attr :width))
+		      ((plist-get attr :height) "")
+		      ((eq float 'figure) "0.7\\textwidth")
+		      ((eq float 'wrap) "0.48\\textwidth")
+		      (t org-latex-image-default-width)))
+	 (height (cond ((plist-get attr :height))
+		       ((or (plist-get attr :width)
+			    (memq float '(figure wrap))) "")
+		       (t org-latex-image-default-height)))
+	 (options (let ((opt (or (plist-get attr :options)
+				 org-latex-image-default-option)))
 		    (if (not (string-match "\\`\\[\\(.*\\)\\]\\'" opt)) opt
 		      (match-string 1 opt))))
 	 image-code)
@@ -2421,9 +2421,8 @@ This function assumes TABLE has `org' as its `:type' property and
 	 ;; Determine alignment string.
 	 (alignment (org-latex--align-string table info))
 	 ;; Determine environment for the table: longtable, tabular...
-	 (table-env (let ((env (plist-get attr :environment)))
-		      (if env (format "%s" env)
-			org-latex-default-table-environment)))
+	 (table-env (or (plist-get attr :environment)
+			org-latex-default-table-environment))
 	 ;; If table is a float, determine environment: table, table*
 	 ;; or sidewaystable.
 	 (float-env (unless (equal "longtable" table-env)
@@ -2436,7 +2435,7 @@ This function assumes TABLE has `org' as its `:type' property and
 			  "table")))))
 	 ;; Extract others display options.
 	 (fontsize (let ((font (plist-get attr :font)))
-		     (and font (concat (org-trim (format "%s" font)) "\n"))))
+		     (and font (concat font "\n"))))
 	 (width (plist-get attr :width))
 	 (placement (or (plist-get attr :placement)
 			(format "[%s]" org-latex-default-figure-position)))
@@ -2527,9 +2526,8 @@ This function assumes TABLE has `org' as its `:type' property and
   (let* ((caption (org-latex--caption/label-string table info))
 	 (attr (org-export-read-attribute :attr_latex table))
 	 (inlinep (eq (plist-get attr :mode) 'inline-math))
-	 (env (let ((env (plist-get attr :environment)))
-		(if env (format "%s" env)
-		  org-latex-default-table-environment)))
+	 (env (or (plist-get attr :environment)
+		  org-latex-default-table-environment))
 	 (contents
 	  (mapconcat
 	   (lambda (row)
@@ -2566,19 +2564,20 @@ This function assumes TABLE has `org' as its `:type' property and
 	   (inlinep "\\(")
 	   ((org-string-nw-p caption) (concat "\\begin{equation}\n" caption))
 	   (t "\\["))
-     ;; Prefix (make sure it is a string).
-     (format "%s" (or (plist-get attr :math-prefix) ""))
+     ;; Prefix.
+     (or (plist-get attr :math-prefix) "")
      ;; Environment.  Also treat special cases.
      (cond ((equal env "array")
 	    (let ((align (org-latex--align-string table info)))
 	      (format "\\begin{array}{%s}\n%s\\end{array}" align contents)))
 	   ((assoc env org-latex-table-matrix-macros)
-	    (format "\\%s%s{\n%s}" env
-		    (format "%s" (or (plist-get attr :math-arguments) ""))
+	    (format "\\%s%s{\n%s}"
+		    env
+		    (or (plist-get attr :math-arguments) "")
 		    contents))
 	   (t (format "\\begin{%s}\n%s\\end{%s}" env contents env)))
-     ;; Suffix (make sure it is a string).
-     (format "%s" (or (plist-get attr :math-suffix) ""))
+     ;; Suffix.
+     (or (plist-get attr :math-suffix) "")
      ;; Closing string.  If TABLE is in the middle of a table cluster,
      ;; do not insert any.  If it closes such a cluster, be sure to
      ;; close the cluster with a string matching the opening string.
diff --git a/lisp/ox-man.el b/lisp/ox-man.el
index 4c17e49..7fc7f02 100644
--- a/lisp/ox-man.el
+++ b/lisp/ox-man.el
@@ -945,28 +945,14 @@ This function assumes TABLE has `org' as its `:type' attribute."
          (lines (org-split-string contents "\n"))
 
          (attr-list
-          (let ((result-list '()))
-            (dolist (attr-item
-                     (list
-                      (if (plist-get attr :expand)
-                          "expand" nil)
-
-                      (case (plist-get attr :placement)
-                        ('center "center")
-                        ('left nil)
-                        (t (if org-man-tables-centered "center" "")))
-
-                      (case (plist-get attr :boxtype)
-                        ('box "box")
-                        ('doublebox "doublebox")
-                        ('allbox "allbox")
-                        ('none nil)
-                        (t "box"))))
-
-              (if attr-item
-                  (add-to-list 'result-list attr-item)))
-            result-list ))
-
+	  (delq nil
+		(list
+		 (and (plist-get attr :expand) "expand")
+		 (let ((placement (plist-get attr :placement)))
+		   (cond ((string= placement 'center) "center")
+			 ((string= placement 'left) nil)
+			 (t (if org-man-tables-centered "center" ""))))
+		 (or (plist-get attr :boxtype) "box"))))
 
          (title-line  (plist-get attr :title-line))
          (long-cells (plist-get attr :long-cells))
diff --git a/lisp/ox-odt.el b/lisp/ox-odt.el
index a1caff7..d9dd525 100644
--- a/lisp/ox-odt.el
+++ b/lisp/ox-odt.el
@@ -2341,12 +2341,19 @@ used as a communication channel."
 	  (list user-frame-style user-frame-attrs user-frame-anchor))
 	 ;; (embed-as (or embed-as user-frame-anchor "paragraph"))
 	 ;; extrac
-	 ;; handle `:width', `:height' and `:scale' properties.
+	 ;;
+	 ;; Handle `:width', `:height' and `:scale' properties.  Read
+	 ;; them as numbers since we need them for computations.
 	 (size (org-odt--image-size
-		src-expanded (plist-get attr-plist :width)
-		(plist-get attr-plist :height)
-		(plist-get attr-plist :scale) nil ;; embed-as
-		"paragraph"			  ; FIXME
+		src-expanded
+		(let ((width (plist-get attr-plist :width)))
+		  (and width (read width)))
+		(let ((length (plist-get attr-plist :length)))
+		  (and length (read length)))
+		(let ((scale (plist-get attr-plist :scale)))
+		  (and scale (read scale)))
+		nil			; embed-as
+		"paragraph"		; FIXME
 		))
 	 (width (car size)) (height (cdr size))
 	 (standalone-link-p (org-odt--standalone-link-p element info))
@@ -3351,8 +3358,9 @@ channel."
 	      "OrgTableHeading")
 	     ((let* ((table (org-export-get-parent-table table-cell))
 		     (table-attrs (org-export-read-attribute :attr_odt table))
-		     (table-header-columns (plist-get table-attrs
-						      :header-columns)))
+		     (table-header-columns
+		      (let ((cols (plist-get table-attrs :header-columns)))
+			(and cols (read cols)))))
 		(<= c (cond ((wholenump table-header-columns)
 			     (- table-header-columns 1))
 			    (table-header-columns 0)
diff --git a/lisp/ox.el b/lisp/ox.el
index 98b7a21..c5b6d7c 100644
--- a/lisp/ox.el
+++ b/lisp/ox.el
@@ -3257,11 +3257,24 @@ that property within attributes.
 
 This function assumes attributes are defined as \":keyword
 value\" pairs.  It is appropriate for `:attr_html' like
-properties."
+properties.  All values will become strings except the empty
+string and \"nil\", which will become nil."
   (let ((attributes
 	 (let ((value (org-element-property attribute element)))
-	   (and value
-		(read (format "(%s)" (mapconcat 'identity value " ")))))))
+	   (when value
+	     (let ((s (mapconcat 'identity value " ")) result)
+	       (while (string-match
+		       "\\(?:^\\|[ \t]+\\)\\(:[-a-zA-Z0-9_]+\\)\\([ \t]+\\|$\\)"
+		       s)
+		 (let ((value (substring s 0 (match-beginning 0))))
+		   (push (and (not (member value '("nil" ""))) value) result))
+		 (push (intern (match-string 1 s)) result)
+		 (setq s (substring s (match-end 0))))
+	       ;; Ignore any string before the first property with `cdr'.
+	       (cdr (nreverse (cons (and (org-string-nw-p s)
+					 (not (equal s "nil"))
+					 s)
+				    result))))))))
     (if property (plist-get attributes property) attributes)))
 
 (defun org-export-get-caption (element &optional shortp)
diff --git a/testing/lisp/test-ox.el b/testing/lisp/test-ox.el
index 6fa1f25..754c657 100644
--- a/testing/lisp/test-ox.el
+++ b/testing/lisp/test-ox.el
@@ -645,12 +645,33 @@ body\n")))
      :attr_html
      (org-test-with-temp-text "#+ATTR_HTML: :a 1 :b 2\nParagraph"
        (org-element-at-point)))
-    '(:a 1 :b 2)))
+    '(:a "1" :b "2")))
   ;; Return nil on empty attribute.
   (should-not
    (org-export-read-attribute
     :attr_html
-    (org-test-with-temp-text "Paragraph" (org-element-at-point)))))
+    (org-test-with-temp-text "Paragraph" (org-element-at-point))))
+  ;; Return nil on "nil" string.
+  (should
+   (equal '(:a nil :b nil)
+	  (org-export-read-attribute
+	   :attr_html
+	   (org-test-with-temp-text "#+ATTR_HTML: :a nil :b nil\nParagraph"
+	     (org-element-at-point)))))
+  ;; Return nil on empty string.
+  (should
+   (equal '(:a nil :b nil)
+	  (org-export-read-attribute
+	   :attr_html
+	   (org-test-with-temp-text "#+ATTR_HTML: :a :b\nParagraph"
+	     (org-element-at-point)))))
+  ;; Ignore text before first property.
+  (should-not
+   (member "ignore"
+	   (org-export-read-attribute
+	    :attr_html
+	    (org-test-with-temp-text "#+ATTR_HTML: ignore :a 1\nParagraph"
+	      (org-element-at-point))))))
 
 (ert-deftest test-org-export/get-caption ()
   "Test `org-export-get-caption' specifications."