[EZ] Fix config bug where interpolation happens too early

[EugenHotaj]

There is currently a bug in config interpolation. E.g. given the following config:

name: REPLACE_ME
output_dir: ${name}/logs

When overriding name=some-override via the CLI, the expected config should be:

name: some-override
output_dir: some-override/logs

However, instead we get:

name: some-override
output_dir: REPLACE_ME/logs

This happens because OmegaConf resolves values under the hood when you try to access them.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.31%. Comparing base (213f386) to head (2bab3ec).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2236      +/-   ##
==========================================
- Coverage   65.41%   64.31%   -1.11%     
==========================================
  Files         344      352       +8     
  Lines       20658    20569      -89     
==========================================
- Hits        13514    13228     -286     
- Misses       7144     7341     +197     

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[RdoubleA]

This is a great catch. You may need to update the unit tests to make sure the mock value returned by OmegaConf.load is an OmegaConf object. Would you also be able to modify test_parse_known_args in tests/torchtune/config/test_parse.py to test for this edge case?

[EugenHotaj]

@RdoubleA added ptal when you get a chance.

[RdoubleA]

awesome, will merge once CI is green

[RdoubleA]

@EugenHotaj looks like one more test needs to be fixed, you can also run tests locally with pytest tests

[EugenHotaj]

Ah missed one of the tests, updated