I'm a bit surprised that so many are advocating custom directives and creating proxy variables being updated by $watch.
Problems like this are the reason that AngularJS filters were made!
From the docs:
A filter formats the value of an expression for display to the user.
We aren't looking to manipulate the data, just format it for display in a different way. So let's make a filter that takes in our rows array, flattens it, and returns the flattened rows.
.filter('flattenRows', function(){
return function(rows) {
var flatten = [];
angular.forEach(rows, function(row){
subrows = row.subrows;
flatten.push(row);
if(subrows){
angular.forEach(subrows, function(subrow){
flatten.push( angular.extend(subrow, {subrow: true}) );
});
}
});
return flatten;
}
})
Now all we need is to add the filter to ngRepeat:
<table class="table table-striped table-hover table-bordered">
<thead>
<tr>
<th>Rows with filter</th>
</tr>
</thead>
<tbody>
<tr ng-repeat="row in rows | flattenRows">
<td>{{row.name}}</td>
</tr>
</tbody>
</table>
You are now free to combine your table with other filters if desired, like a search.
While the multiple tbody approach is handy, and valid, it will mess up any css that relies on the order or index of child rows, such as a "striped" table and also makes the assumption that you haven't styled your tbody in a way that you don't want repeated.
Here's a plunk: http://embed.plnkr.co/otjeQv7z0rifPusneJ0F/preview
Edit:I added a subrow value and used it in the table to show which rows are subrows, as you indicated a concern for being able to do that.