Implement gRPC Simulate endpoint

[amaury1093]

Description

closes: #5922

---

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• Targeted PR against correct branch (see CONTRIBUTING.md)
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• Code follows the module structure standards.
• Wrote unit and integration tests
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• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #7035 into master will decrease coverage by 0.24%.
The diff coverage is 35.25%.

@@            Coverage Diff             @@
##           master    #7035      +/-   ##
==========================================
- Coverage   54.96%   54.72%   -0.25%     
==========================================
  Files         560      563       +3     
  Lines       38188    38405     +217     
==========================================
+ Hits        20989    21016      +27     
- Misses      15495    15681     +186     
- Partials     1704     1708       +4     

[fedekunze]

utACK. I still don't know how to use this simulate. Adding docs for it would be nice

[amaury1093]

I ran into some nasty import cycles, in tests only:

import cycle not allowed in test
package github.com/cosmos/cosmos-sdk/x/auth/tx (test)
    imports github.com/cosmos/cosmos-sdk/std
    imports github.com/cosmos/cosmos-sdk/baseapp
    imports github.com/cosmos/cosmos-sdk/client/grpc/simulate
    imports github.com/cosmos/cosmos-sdk/x/auth/tx
FAIL    github.com/cosmos/cosmos-sdk/x/auth/tx [setup failed]

All imports made sense to me, except maybe std imports baseapp. So I refactored:

• remove mention of baseapp from std
• put std/consensus_params.go into params keeper
• remove mention of types/module from std (another import cycle)
• this function MakeCodec was only used in tests in simapp, so that's where I put it.

[amaury1093]

@fedekunze yes, I agree some docs would be nice. But I'm not 100% sure where to put them. And I'm not sure also how these docs would actually look like: this endpoint is just another endpoint amongst all the gRPC endpoints we have, maybe some unified client request docs would make more sense (i.e. either send a gRPC request to the gRPC server, or send a HTTP request to the gateway server).

cc @clevinson

[alexanderbez]

Excellent work @amaurymartiny 👏

[alexanderbez]

Not sure if we want to wait on @aaronc's review. Feel free to merge whenever you'd like.

[aaronc]

This shouldn't be in base, it should be in cosmos.tx

[aaronc]

Let's fix this when we address #7355. Originally this was in a single tx Service in #6872. Ideally those are the same gRPC service. I'm not sure why we would need to separate them.

[amaury1093]

True, this endpoint could definitely go in with those in #7355

Note: there are some other TM rpc methods which we might or might not want to wrap under gRPC at some point. To avoid having too many services, we could regroup them under one big module-agnostic service, maybe not called Tx though. There's also the reflection service, which could also be merged into it.

[aaronc]

Let's bundle together stuff that is related. Simulate, get tx by hash, etc. all depend on Tx. The original tx Service was intended to cover all that stuff. Reflection doesn't depend on Tx so IMHO should remain separate.

[amaury1093]

Right, I was pointing out that our bundling will then be different than TM's bundling (e.g. getTxByHash goes in Info, not in Tx, see link above), which might be confusing for people, esp. if one day TM has its own gRPC.