html: Implement fat table rows (use tbodies to represent separators)

html does not support table separator rows as Org mode does. Emacs org export
simulates rows as defined by separators by wrapping all the rows between 2
separators into a separate tbody. The html spec is fine with that [0] so we
follow.

[0] https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tbody

org/html_writer.go

@@ -459,23 +459,31 @@ func (w *HTMLWriter) WriteNodeWithName(n NodeWithName) {
 
 func (w *HTMLWriter) WriteTable(t Table) {
 	w.WriteString("<table>\n")
-	beforeFirstContentRow := true
+	inHead := len(t.SeparatorIndices) > 0 &&
+		t.SeparatorIndices[0] != len(t.Rows)-1 &&
+		(t.SeparatorIndices[0] != 0 || len(t.SeparatorIndices) > 1 && t.SeparatorIndices[len(t.SeparatorIndices)-1] != len(t.Rows)-1)
+	if inHead {
+		w.WriteString("<thead>\n")
+	} else {
+		w.WriteString("<tbody>\n")
+	}
 	for i, row := range t.Rows {
-		if row.IsSpecial || len(row.Columns) == 0 {
+		if len(row.Columns) == 0 && i != 0 && i != len(t.Rows)-1 {
-			continue
+			if inHead {
-		}
-		if beforeFirstContentRow {
-			beforeFirstContentRow = false
-			if i+1 < len(t.Rows) && len(t.Rows[i+1].Columns) == 0 {
-				w.WriteString("<thead>\n")
-				w.writeTableColumns(row.Columns, "th")
 				w.WriteString("</thead>\n<tbody>\n")
-				continue
+				inHead = false
 			} else {
-				w.WriteString("<tbody>\n")
+				w.WriteString("</tbody>\n<tbody>\n")
 			}
 		}
-		w.writeTableColumns(row.Columns, "td")
+		if row.IsSpecial {
+			continue
+		}
+		if inHead {
+			w.writeTableColumns(row.Columns, "th")
+		} else {
+			w.writeTableColumns(row.Columns, "td")
+		}
 	}
 	w.WriteString("</tbody>\n</table>\n")
 }

org/testdata/options.html

@@ -29,6 +29,8 @@ As buffer options are merged with the defaults, the above headline will be expor
 <td>toc</td>
 <td>Include table of contents (outline)</td>
 </tr>
+</tbody>
+<tbody>
 <tr>
 <td>pri</td>
 <td>Include priority <code class="verbatim">[#A]</code>, <code class="verbatim">[#B]</code>, <code class="verbatim">[#C]</code> in headline title</td>

org/testdata/tables.html

@@ -151,3 +151,43 @@ table with aligned and sized columns
 table with right aligned columns (because numbers)
 </figcaption>
 </figure>
+<figure>
+<table>
+<thead>
+<tr>
+<th class="align-right">a</th>
+<th class="align-right">b</th>
+<th class="align-right">c</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td class="align-right">1</td>
+<td class="align-right">2</td>
+<td class="align-right">3</td>
+</tr>
+<tr>
+<td class="align-right">.</td>
+<td class="align-right">.</td>
+<td class="align-right">.</td>
+</tr>
+</tbody>
+<tbody>
+<tr>
+<td class="align-right">1</td>
+<td class="align-right">2</td>
+<td class="align-right">3</td>
+</tr>
+</tbody>
+<tbody>
+<tr>
+<td class="align-right">1</td>
+<td class="align-right">2</td>
+<td class="align-right">3</td>
+</tr>
+</tbody>
+</table>
+<figcaption>
+table with multiple separators (~ multiple tbodies)
+</figcaption>
+</figure>

org/testdata/tables.org

@@ -36,3 +36,13 @@
 | long column a | long column b | long column c |
 |---------------+---------------+---------------|
 |             1 |             2 |             3 |
+
+#+CAPTION: table with multiple separators (~ multiple tbodies)
+| a | b | c |
+|---+---+---|
+| 1 | 2 | 3 |
+| . | . | . |
+|---+---+---|
+| 1 | 2 | 3 |
+|---+---+---|
+| 1 | 2 | 3 |

org/testdata/tables.pretty_org

@@ -36,3 +36,13 @@
 | long column a | long column b | long column c |
 |---------------+---------------+---------------|
 |             1 |             2 |             3 |
+
+#+CAPTION: table with multiple separators (~ multiple tbodies)
+| a | b | c |
+|---+---+---|
+| 1 | 2 | 3 |
+| . | . | . |
+|---+---+---|
+| 1 | 2 | 3 |
+|---+---+---|
+| 1 | 2 | 3 |