feat(server): add custom start handler

[julienrbrt]

Description

Support custom starting app logic. This allows forks of the SDK only modifying the start command to only replace their start logic. Backport to v0.50 won't contain the api improvements (breakage) but will be additive only.

Use case:

Replace the need a forking the sdk for things like: release/v0.50.x...rollkit:cosmos-sdk:release/v0.50.x

How to use:

Set StartCommandHandler and AddFlags in StartCmdOptions when calling AddCommands.

Why method like startAPIServer, startGrpcServer or other private methods in start.go are not simply public to make creating StartCommandHandler less verbose?

Because we do not to provide any api guarantee for those functions. If you are re-implementing SDK's start command, you should know what you are doing and can reimplement those functions yourself.

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Summary by CodeRabbit

• New Features
  • Added customizability to the server's start command for enhanced flexibility.
• Changes
  • Streamlined server module operations by enabling callback into the application struct post-setup.
  • Simplified function calls in the building apps documentation by removing specific parameters.
  • Refactored server startup logic to improve code efficiency and error handling.
• Bug Fixes
  • Ensured consistency in the PreBlock function by adjusting its return type.
• Refactor
  • Removed outdated concepts such as basic manager and ModuleInitFlags to clean up the codebase.
  • Updated command addition functions to support new start command customization options.
  • Adjusted command initialization in the simulation application for clarity and efficiency.
• Documentation
  • Updated building apps documentation to reflect changes in function call parameters.

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Commits

Files that changed from the base of the PR and between 00b2b9d and 50b4e95.

Walkthrough

The recent updates across various components of the cosmos-sdk focus on simplifying and enhancing customization and consistency. Key changes include the introduction of customizable start command handlers, the removal of the basic manager concept and ModuleInitFlags, and the streamlining of function calls and parameters across the server module and application testnet setup. These adjustments aim to improve developer experience and reduce complexity in application configuration and command handling.

Changes

File(s)	Summary
CHANGELOG.md, server/types/app.go	- Customizable start command in server module. - Simplified PreBlock return type. - Enhanced callback capability in PostSetup. - Removed basic manager and ModuleInitFlags. - Removed unnecessary imports and parameters related to cobra, codec, and codectypes.
docs/build/.../05-app-testnet.md	- Simplified function calls by removing createMerlinAppAndExport and addModuleInitFlags.
server/start.go, server/util.go	- Introduced StartCommandHandler for custom command handling. - Refactored start functions and AddCommands to use StartCmdOptions. - Adjusted function signatures and logic for efficiency and better error handling.
simapp/simd/cmd/commands.go, simapp/simd/cmd/root.go, simapp/simd/cmd/root_di.go	- Streamlined initRootCmd and NewRootCmd function calls.

Related issues

• Issue [Epic]: Server/v2 #18282
  Refactors the Cosmos SDK server to be modular, allowing for the composition of servers with existing modules or creating new ones without forking the SDK. The changes in this PR align with the objective of cleaning up and minimizing existing interfaces to facilitate integration of new consensus engines and ensure modularity in server components.

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[julienrbrt]

We had two ways to do the same things for flags: Using StartCmdOptions and setting AddFlags and then calling StartCmdWithOptions. Or use AddCommands with custom flags on the start command. This concatenates the possibilities in one.
Note, the backport to v0.50 won't contain that breaking change ( AddCommandsWithStartCmdOptions will do what AddCommands does for v0.51)

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Review Status

Actionable comments generated: 7

Configuration used: .coderabbit.yml

Commits

Files that changed from the base of the PR and between 00b2b9d and de52a81.

Files selected for processing (8)

• CHANGELOG.md (2 hunks)
• docs/build/building-apps/05-app-testnet.md (1 hunks)
• server/start.go (12 hunks)
• server/types/app.go (2 hunks)
• server/util.go (3 hunks)
• simapp/simd/cmd/commands.go (3 hunks)
• simapp/simd/cmd/root.go (1 hunks)
• simapp/simd/cmd/root_di.go (1 hunks)

Additional comments: 12

server/types/app.go (1)

• 8-13: > 📝 NOTE

This review was outside the diff hunks, and no overlapping diff hunk was found. Original lines [1-1]

The removal of ModuleInitFlags and the cobra import aligns with the PR's objectives to simplify the server module's API and reduce dependencies. This change should help in enhancing customization and reducing the need for forking the SDK.

simapp/simd/cmd/root_di.go (1)

• 90-90: The modification of the initRootCmd call to pass fewer arguments contributes to simplifying the codebase and aligns with the PR's objectives of enhancing maintainability and readability.

simapp/simd/cmd/root.go (1)

• 113-113: The modification of the initRootCmd call to pass different arguments contributes to simplifying the codebase and aligns with the PR's objectives of enhancing maintainability and readability.

simapp/simd/cmd/commands.go (1)

• 50-50: The modification of function calls to use server.StartCmdOptions instead of types.ModuleInitFlags contributes to simplifying the codebase and aligns with the PR's objectives of enhancing maintainability and readability.

server/util.go (2)

• 327-327: The addition of opts StartCmdOptions[T] to the AddCommands function enhances customization and aligns with the PR's objectives of simplifying the codebase and reducing the need for forking.
• 353-357: The introduction of the AddCommandsWithStartCmdOptions function, while marked as deprecated, aims to streamline adding server commands with StartCmdOptions. It's important to clarify the deprecation notice to guide developers towards using the preferred AddCommands method directly.

server/start.go (6)

• 127-128: The addition of StartCommandHandler in StartCmdOptions struct enables customization of the start command handler. This is a key feature for allowing developers to inject custom logic at the application start, aligning with the PR's objectives to enhance flexibility without needing to fork the SDK.
• 144-146: The default assignment of start to StartCommandHandler if none is provided ensures backward compatibility and a sensible default behavior. This approach is thoughtful, as it maintains the existing functionality for users who do not need custom start logic.
• 196-196: The invocation of opts.StartCommandHandler within the RunE function of the start command is correctly implemented. It allows for the execution of either the default or a custom start handler based on the configuration provided in opts. This is a crucial integration point for the new feature.
• 615-615: The removal of the home parameter from the testnetify function and the enhanced error handling within it are positive changes. They contribute to simplifying the function's interface and improving its robustness. Ensure that all invocations of testnetify have been updated accordingly.
• 642-644: The default assignment of start to StartCommandHandler in the InPlaceTestnetCreator function mirrors the approach taken in StartCmdWithOptions. This consistency in handling default behavior across different commands is commendable.
• 710-710: The use of opts.StartCommandHandler within the InPlaceTestnetCreator command ensures that the custom start logic can also be applied to testnet creation. This integration extends the flexibility of the new feature to different aspects of the SDK's functionality.

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Review Status

Actionable comments generated: 0

Configuration used: .coderabbit.yml

Commits

Files that changed from the base of the PR and between de52a81 and 91d6336.

Files selected for processing (1)

• UPGRADING.md (1 hunks)

Additional comments: 2

UPGRADING.md (2)

• 34-39: The code snippet provided for simplifying the start command is clear and correctly demonstrates the change from a function call to struct initialization. This change should streamline the process for developers and make the codebase more maintainable.
• 31-43: > 📝 NOTE

This review was outside the diff hunks and was mapped to the diff hunk with the greatest overlap. Original lines [1-1206]

While the document is technically accurate and provides clear upgrade instructions, it's recommended to perform a thorough grammar and spell check outside of code blocks and technical terms. This will enhance the readability and professionalism of the document. Consider using a professional text editor or grammar checking tool to identify and correct these issues.

[likhita-809]

lgtm