Allow Caption field as Formatted HTML

Looks good for me. Maybe the existing table field defaults in the content type settings and table field values on existing content should be converted (preferably to Plain text format if it exists) in a hook_update_N().

You should provide a new hook_update_N() as function tablefield_update_7007() instead of inserting code in the existing tablefield_update_7003().

This is a nice improvement! I saw the patch #7 and found some points.

1.

+   // Change the default field for each content type.
+  $field_names = array();

We need to set a proper field names here, right? Or, you can use field_read_fields(['type' => 'tablefield']) and $field['storage']['details'] to get table names for Tablefield fields.

2.

+        // Rationalize the table data.
+        if (!empty($instance)) {
+          // Remove extraneous data.
+          $count_cols = $instance['rebuild']['count_cols'];
+          $count_rows = $instance['rebuild']['count_rows'];
+          $caption = $instance['caption'];
+          $rebuild = $instance['rebuild'];
+          $import = $instance['import'];
+          $paste = $instance['paste'];
+          unset($instance['caption']);
+          unset($instance['rebuild']);
+          unset($instance['import']);
+          unset($instance['paste']);
+        }
+
+        // Changing Caption format values for old data.
+        if (!is_array($caption)) {
+          $captionArray['value'] = $caption;
+          $captionArray['format'] = 'plain_text';
+          $caption = $captionArray;
+        }
+        // Recreate previous removed data.
+        $instance['caption'] = $caption;
+        $instance['rebuild'] = $rebuild;
+        $instance['import'] = $import;
+        $instance['paste'] = $paste;

What does part do? It seems we don't need to re-set rebuild, import and paste here. All we want to change is caption, right?

Drupal 7 is no longer supported. If this applies to a supported version, please re-open.