Settingsloader: Fail on Error

[SmithChart]

Loading settings is a very early step when starting up Lona. In case that a settings file or a settings override can not be loaded or parsed Lona currently continues to start. But will very likely not be configured in a way that the user expect or want. For example:

$ lona run-server -s does_not_exist.py
MainThread                     ERROR    11:39:42.919306 lona.settings exception raised while loading settings '/home/chris/(...)/does_not_exist.py'
  Traceback (most recent call last):                                                                                                                                                                                                                                                                                
    File "/home/chris/(...)/env/lib/python3.13/site-packages/lona/settings.py", line 26, in add                                                                                                                                                                                         
      values = runpy.run_path(                                                                                                                                                                                                                                                                                      
          path,                                                                                                                                                                                                                                                                                                     
          init_globals=self._values,                                                                                                                                                                                                                                                                                
          run_name=path,                                                                                                                                                                                                                                                                                            
      )                                                                                                                                                                                                                                                                                                             
    File "<frozen runpy>", line 286, in run_path                                                                                                                                                                                                                                                                    
    File "<frozen runpy>", line 254, in _get_code_from_file                                                                                                                                                                                                                                                         
  FileNotFoundError: [Errno 2] No such file or directory: '/home/chris/(...)/does_not_exist.py'                                                                                                                                                                                         
MainThread                     WARNING  11:39:42.920526 lona.server routing table is empty
/home/chris/(...)/env/lib/python3.13/site-packages/lona/templating.py:44: Lona_2_0_DeprecationWarning: client_version() will be removed in 2.0
  lona.warnings.remove_2_0()
======== Running on http://localhost:8080 ========
(Press CTRL+C to quit)

With this change Lona will simply refuse to start up and exit with rc=1.
This way a script or service running Lona can catch and report the misconfiguration:

lona run-server -s does_not_exist.py; echo $?
MainThread                     ERROR    11:31:59.257469 lona.settings exception raised while loading settings '/home/chris/(...)/does_not_exist.py'
  Traceback (most recent call last):                                                                                                                                                                                                                                                                                
    File "/home/chris/(...)/env/lib/python3.13/site-packages/lona/settings.py", line 27, in add                                                                                                                                                                                         
      values = runpy.run_path(                                                                                                                                                                                                                                                                                      
          path,                                                                                                                                                                                                                                                                                                     
          init_globals=self._values,                                                                                                                                                                                                                                                                                
          run_name=path,                                                                                                                                                                                                                                                                                            
      )                                                                                                                                                                                                                                                                                                             
    File "<frozen runpy>", line 286, in run_path                                                                                                                                                                                                                                                                    
    File "<frozen runpy>", line 254, in _get_code_from_file                                                                                                                                                                                                                                                         
  FileNotFoundError: [Errno 2] No such file or directory: '/home/chris/(...)/does_not_exist.py'                                                                                                                                                                                         
1

[SmithChart]

It has been some time since we had any activity on this project :-)

So: Before I start wrestling the rest of the CI failures here: Is there any interesting in merging fixes like this and maybe even make a new release of Lona?

[fscherf]

Hey @SmithChart!

Long time no see :) thx for this fix!

Absolutely! You are right, traffic on this project was pretty low for a long time now, but only because it is (somewhat) done 🤷 It does everything that I needed it to do and it never stopped working. I still get emails from people with questions regulary, so people never stopped using it.

I'd be happy to release a new version for you after we get this PR merged.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

❌ Patch coverage is 20.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.23%. Comparing base (0ff6921) to head (fbdafc1).
⚠️ Report is 92 commits behind head on master.

Files with missing lines	Patch %	Lines
lona/command_line/handle_command_line.py	0.00%	2 Missing ⚠️
lona/settings.py	33.33%	2 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #633      +/-   ##
==========================================
+ Coverage   73.12%   73.23%   +0.10%     
==========================================
  Files          88       88              
  Lines        6128     6130       +2     
  Branches     1328     1328              
==========================================
+ Hits         4481     4489       +8     
+ Misses       1364     1361       -3     
+ Partials      283      280       -3     

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[fscherf]

@SmithChart I fixed the CI problems.
In general, I agree with the patches, I'm not sure whether doing a hard sys.exit in a high-level module like settings is the right thing to do here. Ideally, we would raise a special exception there that is then handled by the cli code by issuing sys.exit.