Load error! (SyntaxError: JSON.parse) - error opening hierarchical structured terms

I got the same error clicking on the first level term trying to get the second level terms.

The error log contained
Class 'Drupal\\Component\\Utility\\HTML' not found in [...]/taxonomy_manager/src/Element/TaxonomyManagerTree.php on line 146

A quick check found that the class is called Drupal\Component\Utility\Html, not HTML.
I also expected HTML to be all uppercase but not here, sir.

Patch attached.

I also changed the issue title.

Adjusted title again because people seem to find issue https://www.drupal.org/node/2681969#comment-11051543 which mixes this error with a completly different one.

Forgot to set status to needs-review

TaxonomyManagerForm also uses Drupal\Component\Utility\HTML

I applied #5 and error changed
FROM:
Load error! (SyntaxError: JSON.parse: unexpected character at line 2 column 1 of the JSON data)

To:
Load error! (Not Found)

using Drupal 8.1.

I applied #5 and error 'Load error! (Not Found)' remains.
Using Drupal 8.1.10

I can confirm this issue still exists on 8.1.10, included screenshot shows what went wrong, according to console :

It seems that it somehow manages to not resolve the request, despite using standard .htaccess rules.

The Load Error 'Load error! (Not Found)' is caused by wrong ajax url in taxonomy_manager/js/tree.js.
The attached patch file fix this bug.

I can confirm this patch works.

Thank you very much.

I have made another iteration on top of joergM's patch: instead of pushing base URL from PHP down to JavaScript, I propose to simply use Drupal.url() JavaScript function to construct the AJAX URL.

#11 works well for me. I also prefer Drupal.url(). It'd be nice to have more reviews for the #11.

Thanks!

#11 works fine - I also prefer Drupal.url() ;-)

Let's make it RTBC, because the patch is really simple and we have a consensus of 3 votes already.

+1 on RTBC for #11

I can also verify that patch #11 solved my json error. (Caused by HTML class not found).

Environment:

Drupal 8.2.1
PhP 7.0

+1 on RTBC for #11

+1 on RTBC for #11

+1 It works, but I had to patch it manually.
Any good tutorial for how to patch "automatically"? I always get something like this

File to patch: tree.js
patching file tree.js
Hunk #1 FAILED at 9.
Hunk #2 FAILED at 143.
2 out of 2 hunks FAILED -- saving rejects to file tree.js.rej
can't find file to patch at input line 40
Perhaps you should have used the -p or --strip option?
The text leading up to this was:
--------------------------
|diff --git a/src/Form/TaxonomyManagerForm.php b/src/Form/TaxonomyManagerForm.php
|index 86b5366..0c45db8 100644
|--- a/src/Form/TaxonomyManagerForm.php
|+++ b/src/Form/TaxonomyManagerForm.php
--------------------------
File to patch: tree.js
patching file tree.js
Hunk #1 FAILED at 13.
Hunk #2 FAILED at 102.
2 out of 2 hunks FAILED -- saving rejects to file tree.js.rej

Patch from #11 works for me...!

Thanks for contributions. The use of Drupal.url() tidies it up.