CodeMirror>5.16 & Safari 10: Strange behavior with spaces

After upgrading CodeMirror to 5.21 (from 5.8) in jupyter/notebook, users started encountering a strange bug on Safari 10. I did some investigating and found that this bug starting affecting notebook when upgrading from CodeMirror 5.16 to 5.17.

Demo:

One of the users determined that code cells (Python syntax, etc.) exhibit this behavior:

• Immediately after any delimiter
  • e.g. =, ,, ., (, ), [, ], {, }, ", ', etc.
• Not within closed delimiters
• Not within compound statement if closed by :
  • e.g. it will occur here if x =={cursor}, but not hereif x =={cursor}:

Markdown cells (Markdown syntax) exhibit this behavior when typing a single space:

• Unless cursor is at start of a new line
• Unless cursor is placed immediately after closed markup delimiter (e.g. *text*{cursor})
• Unless within markup delimiters (e.g. *text{cursor}*)

Here is a list commits included in 5.17: https://github.com/codemirror/CodeMirror/commits/master?after=Y3Vyc29yOjiTKo4zLKAvc9OV%2BJnP36dpIuEyKzIwOQ%3D%3D

I have a feeling that this commit might be the culprit although I haven’t been able to resolve this by simply reversing the changes in this commit: https://github.com/codemirror/CodeMirror/commit/2c913e5d2914fdc64df80031544a384940006feb

[minrk]

5.22.1 doesn’t appear to exist, but 5.22.2 is on bower now, the first release produced by the automated bower packaging.

[gnestor]

I was able to isolate this bug to this commit: https://github.com/codemirror/CodeMirror/commit/e60f4b7dd88b71e227f79200932c028ca047d78e

@marijnh Any idea why this commit would cause the insertion of single spaces to not move the cursor (and then the cursor jumps to the proper position on a subsequent space)?