LegacyAminoPubKey loses keys on unmarshalling

[haasted]

Summary of Bug

LegacyAminoPubKey fails to correctly unmarshal from JSON.

Version

v0.42.9

Steps to Reproduce

The test TestAminoUnmarshalJSON in https://github.com/cosmos/cosmos-sdk/blob/v0.42.9/crypto/keys/multisig/multisig_test.go should be amended with the following line:

require.Equal(t, 5, len(pk.(*kmultisig.LegacyAminoPubKey).PubKeys))

This adds a condition that the public keys have been deserialized correctly and will demonstrate the issue.

Potential fix

To solve the issue for ourselves, I have made a temporary fork of the SDK. A potential fix can be found in this commit: e-money@a3c8dea

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For Admin Use

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[jgimeno]

Feel free to open a PR @haasted against the repo.

[robert-zaremba]

ACK. The issue is in master as well.

[robert-zaremba]

With @AmauryM we are concluding that this is not a good solution and is creating a regression. See the test failing in: #10042

We need to release v0.44.1 so we will revert the commit from release/v0.44.x branch (but keep the one in master) and let's try to investigate it further.

[blewater]

Hi 👋, I created PR #10275 against the previous attempt to address the regression issue. Please advise whether the PR suffices for continuing the review process.