Problem: rpc can't query old parameter format after migration

[adu-crypto]

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close: #806 By querying params from x/params if we get nil from x/cronos store, we could return correct params even if the context is in old blocks before the params migratiion

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[codecov[bot]]

Codecov Report

Merging #807 (40d3fcf) into main (6365729) will increase coverage by 0.14%. The diff coverage is 80.00%.

:exclamation: Current head 40d3fcf differs from pull request most recent head befb56e. Consider uploading reports for the commit befb56e to get more accurate results

@@            Coverage Diff             @@
##             main     #807      +/-   ##
==========================================
+ Coverage   34.26%   34.40%   +0.14%     
==========================================
  Files          30       30              
  Lines        1582     1587       +5     
==========================================
+ Hits          542      546       +4     
- Misses        983      984       +1     
  Partials       57       57              

Impacted Files	Coverage Δ
x/cronos/keeper/params.go	71.42% <0.00%> (-2.11%)	:arrow_down:
x/cronos/keeper/keeper.go	76.60% <100.00%> (+0.56%)	:arrow_up:

[thomas-nguy]

the issue is that we cannot query params after migration for older blocks?

[adu-crypto]

yes, the issue is that we can query params for blocks after the migration, but if we switched context to older blocks, we can not get params because params are not stored in x/cronos store at that time.

[adu-crypto]

lgtm, maybe you could add a test in the python integration tests "test_upgrade.py" (just query params with older ctx after the upgrade)

good idea, I'll add it

[yihuang]

But in this way we have to stick with x/params, not sure what to do when that is finally removed. it's really a tricky issue that to support query old blocks when this kind of migration happens, don't have a good idea yet.

[adu-crypto]

yes, given we support querying params for old blocks for the params migration, maybe we should consider making other code changes in the future compatible with the old blocks data?