The FileSystem API doesn't seem well suited for the task of a full recursive traversal, perhaps that's part of the reason why other vendors are not adopting it. Anyway, with an arcane combination of Promises I think I was able to accomplish this goal:
function traverse_directory(entry) {
let reader = entry.createReader();
// Resolved when the entire directory is traversed
return new Promise((resolve_directory) => {
var iteration_attempts = [];
(function read_entries() {
// According to the FileSystem API spec, readEntries() must be called until
// it calls the callback with an empty array. Seriously??
reader.readEntries((entries) => {
if (!entries.length) {
// Done iterating this particular directory
resolve_directory(Promise.all(iteration_attempts));
} else {
// Add a list of promises for each directory entry. If the entry is itself
// a directory, then that promise won't resolve until it is fully traversed.
iteration_attempts.push(Promise.all(entries.map((entry) => {
if (entry.isFile) {
// DO SOMETHING WITH FILES
return entry;
} else {
// DO SOMETHING WITH DIRECTORIES
return traverse_directory(entry);
}
})));
// Try calling readEntries() again for the same dir, according to spec
read_entries();
}
}, errorHandler );
})();
});
}
traverse_directory(my_directory_entry).then(()=> {
// AT THIS POINT THE DIRECTORY SHOULD BE FULLY TRAVERSED.
});