Trim all newlines after the final one when saving a file causes Spyder to freeze when saving a blank file

[battaglia01]

Issue Report Checklist

• [:)] Searched the issues page for similar reports
• [:)] Read the relevant sections of the Spyder Troubleshooting Guide and followed its advice
• [:)] Reproduced the issue after updating with conda update spyder (or pip, if not using Anaconda)
• [:)] Could not reproduce inside jupyter qtconsole (if console-related)
• [:)] Tried basic troubleshooting (if a bug/error)
  • [:)] Restarted Spyder
  • [:)] Reset preferences with spyder --reset
  • Reinstalled the latest version of Anaconda
  • [:)] Tried the other applicable steps from the Troubleshooting Guide
• [:)] Completed the Problem Description, Steps to Reproduce and Version sections below

Problem Description

If you set the "Trim all newlines after the final one when saving a file" preference, then saving a blank file causes Spyder to totally hang.

I think this is maybe the cause of these bug reports:
#14926
#15284

You won't get this symptom with the default Spyder preferences (as of 5.0.5) which explains the lack of reproducibility.

Versions

Spyder 5.0.5
Python 3.9.5 64-bit | Qt 5.9.7 | PyQt5 5.9.2 | Darwin 17.7.0

Dependencies

# Mandatory:
applaunchservices >=0.1.7     :  0.2.1 (OK)
atomicwrites >=1.2.0          :  1.4.0 (OK)
chardet >=2.0.0               :  4.0.0 (OK)
cloudpickle >=0.5.0           :  1.6.0 (OK)
cookiecutter >=1.6.0          :  1.7.2 (OK)
diff_match_patch >=20181111   :  20200713 (OK)
intervaltree >=3.0.2          :  3.1.0 (OK)
IPython >=7.6.0               :  7.22.0 (OK)
jedi =0.17.2                  :  0.17.2 (OK)
jsonschema >=3.2.0            :  3.2.0 (OK)
keyring >=17.0.0              :  23.0.1 (OK)
nbconvert >=4.0               :  6.1.0 (OK)
numpydoc >=0.6.0              :  1.1.0 (OK)
parso =0.7.0                  :  0.7.0 (OK)
pexpect >=4.4.0               :  4.8.0 (OK)
pickleshare >=0.4             :  0.7.5 (OK)
psutil >=5.3                  :  5.8.0 (OK)
pygments >=2.0                :  2.9.0 (OK)
pylint >=1.0                  :  2.9.5 (OK)
pyls >=0.36.2;<1.0.0          :  0.36.2 (OK)
pyls_black >=0.4.6            :  0.4.6 (OK)
pyls_spyder >=0.3.2;<0.4.0    :  0.3.2 (OK)
qdarkstyle =3.0.2             :  3.0.2 (OK)
qstylizer >=0.1.10            :  0.1.10 (OK)
qtawesome >=1.0.2             :  1.0.2 (OK)
qtconsole >=5.1.0             :  5.1.1 (OK)
qtpy >=1.5.0                  :  1.9.0 (OK)
rtree >=0.9.7                 :  0.9.7 (OK)
setuptools >=39.0.0           :  52.0.0.post20210125 (OK)
sphinx >=0.6.6                :  4.0.2 (OK)
spyder_kernels >=2.0.4;<2.1.0 :  2.0.5 (OK)
textdistance >=4.2.0          :  4.2.1 (OK)
three_merge >=0.1.1           :  0.1.1 (OK)
watchdog >=0.10.3             :  2.1.3 (OK)
zmq >=17                      :  20.0.0 (OK)

# Optional:
cython >=0.21                 :  0.29.24 (OK)
matplotlib >=2.0.0            :  3.3.4 (OK)
numpy >=1.7                   :  1.20.3 (OK)
pandas >=1.1.1                :  1.3.0 (OK)
scipy >=0.17.0                :  1.6.2 (OK)
sympy >=0.7.3                 :  1.8 (OK)

[ccordoba12]

Hey @battaglia01, thanks for reporting. I could reproduce this problem and will try to fix it soon.

[battaglia01]

Good stuff, thanks!

[ccordoba12]

No prob. This was a very serious issue because it froze the interface completely. And the fix turned out to be not so hard.