[Bug Fix] Stop accessing underlying storage for checking encoder existence

[AbhinavTuli]

🚀 🚀 Pull Request

Checklist:

• My code follows the style guidelines of this project and the Contributing document
• I have commented my code, particularly in hard-to-understand areas
• I have kept the coverage-rate up
• I have performed a self-review of my own code and resolved any problems
• I have checked to ensure there aren't any other open Pull Requests for the same change
• I have described and made corresponding changes to the relevant documentation
• New and existing unit tests pass locally with my changes

Changes

[codecov]

Codecov Report

Merging #1417 (924aafc) into main (5662c3a) will decrease coverage by 0.08%.
The diff coverage is 77.08%.

@@            Coverage Diff             @@
##             main    #1417      +/-   ##
==========================================
- Coverage   92.33%   92.24%   -0.09%     
==========================================
  Files         176      176              
  Lines       14204    14227      +23     
==========================================
+ Hits        13115    13124       +9     
- Misses       1089     1103      +14     

Flag	Coverage Δ
unittests	92.24% <77.08%> (-0.09%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
hub/core/chunk_engine.py	95.22% <77.08%> (-1.46%)	⬇️
hub/core/storage/s3.py	71.91% <0.00%> (-1.69%)	⬇️
hub/core/lock.py	83.60% <0.00%> (-1.64%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5662c3a...924aafc. Read the comment docs.

[farizrahman4u]

If tile encoder does not exist and the storage is in read only mode, I am not sure we should be setting / returning an empty encoder that is not persistent. Should probably return None (and the calling method should check for None).

[AbhinavTuli]

checking for None won't work as that is the default value. To prevent multiple reads from storage we're checking self._tile_encoder to not be None. Persistence shouldn't be an issue as this only happens for read only.
If the user switches mode and tries to write, we will synchronize when the user does his first write in add_cachables_to_cache_dirty_keys