Fix rendering in table with empty cells

`find_emph_char` returns 0 if the char specified is not found in the
current line, but this is also what happens when there's an empty
cell. This patch adds logic to work around this problem.

See MacDownApp/macdown#321

src/document.c

@@ -2225,7 +2225,15 @@ parse_table_row(
 		cell_start = i;
 
 		len = find_emph_char(data + i, size - i, '|');
-		i += len ? len : size - i;
+
+		/* Two possibilities for len == 0:
+		   1) No more pipe char found in the current line.
+		   2) The next pipe is right after the current one, i.e. empty cell.
+		   For case 1, we skip to the end of line; for case 2 we just continue.
+		*/
+		if (len == 0 && data[i] != '|')
+			len = size - i;
+		i += len;
 
 		cell_end = i - 1;
 

test/Tests/Table.html

@@ -0,0 +1,66 @@
+<h1>Standard table</h1>
+
+<table>
+  <thead>
+    <tr>
+      <th>headline1</th>
+      <th>headline2</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>123</td>
+      <td></td>
+    </tr>
+  </tbody>
+</table>
+
+
+<h1>Cell alignment</h1>
+
+<table>
+  <thead>
+    <tr>
+      <th style="text-align: left">headline1</th>
+      <th style="text-align: center">headline2</th>
+      <th style="text-align: right">headline3</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td style="text-align: left">123</td>
+      <td style="text-align: center"></td>
+      <td style="text-align: right"></td>
+    </tr>
+  </tbody>
+</table>
+
+
+<h1>Malformed table: missing cell at row in body</h1>
+
+<table>
+  <thead>
+    <tr>
+      <th>headline1</th>
+      <th>headline2</th>
+      <th>headline3</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>12</td>
+      <td></td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>34</td>
+      <td></td>
+      <td></td>
+    </tr>
+    <tr>
+      <td>56</td>
+      <td></td>
+      <td></td>
+    </tr>
+  </tbody>
+</table>

test/Tests/Table.text

@@ -0,0 +1,21 @@
+# Standard table
+
+|headline1|headline2|
+|---------|---------|
+|123      |         |
+
+
+# Cell alignment
+
+|headline1|headline2|headline3|
+|:-------|:------:|------:|
+|123|||
+
+
+# Malformed table: missing cell at row in body
+
+|headline1|headline2|headline3|
+|-------|-------|-------|
+|12
+|34||
+|56|

test/config.json

@@ -106,6 +106,11 @@
             "input": "Tests/Underline.text",
             "output": "Tests/Underline.html",
             "flags": ["--underline"]
+        },
+        {
+            "input": "Tests/Table.text",
+            "output": "Tests/Table.html",
+            "flags": ["--tables"]
         }
     ]
 }