refactor(types)!: remove handler and update docs (backport #17358) (#17366)

Co-authored-by: Julien Robert <julien@rbrt.fr>

CHANGELOG.md

@@ -65,6 +65,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### API Breaking Changes
 
+* (types) [#17358](https://github.com/cosmos/cosmos-sdk/pull/17358) Remove deprecated `sdk.Handler`, use `baseapp.MsgServiceHandler` instead.
 * (client) [#17197](https://github.com/cosmos/cosmos-sdk/pull/17197) `keys.Commands` does not take a home directory anymore. It is inferred from the root command.
 * (x/staking) [#17098](https://github.com/cosmos/cosmos-sdk/pull/17098) `NewMsgCreateValidator`, `NewValidator`, `NewMsgCancelUnbondingDelegation`, `NewMsgUndelegate`, `NewMsgBeginRedelegate`, `NewMsgDelegate` and `NewMsgEditValidator`  takes a string instead of `sdk.ValAddress` or `sdk.AccAddress`:
     * `NewMsgCreateValidator.Validate()` takes an address codec in order to decode the address.

docs/docs/building-modules/01-module-manager.md

@@ -261,7 +261,6 @@ The module manager is used throughout the application whenever an action on a co
 * `SetOrderPrepareCheckStaters(moduleNames ...string)`: Sets the order in which the `PrepareCheckState()` function of each module will be called during commit of each block. This function is generally called from the application's main [constructor function](../basics/00-app-anatomy.md#constructor-function).
 * `SetOrderMigrations(moduleNames ...string)`: Sets the order of migrations to be run. If not set then migrations will be run with an order defined in `DefaultMigrationsOrder`.
 * `RegisterInvariants(ir sdk.InvariantRegistry)`: Registers the [invariants](./07-invariants.md) of module implementing the `HasInvariants` interface.
-* `RegisterRoutes(router sdk.Router, queryRouter sdk.QueryRouter, legacyQuerierCdc *codec.LegacyAmino)`: Registers legacy [`Msg`](./02-messages-and-queries.md#messages) and [`querier`](./04-query-services.md#legacy-queriers) routes.
 * `RegisterServices(cfg Configurator)`: Registers the services of modules implementing the `HasServices` interface.
 * `InitGenesis(ctx context.Context, cdc codec.JSONCodec, genesisData map[string]json.RawMessage)`: Calls the [`InitGenesis`](./08-genesis.md#initgenesis) function of each module when the application is first started, in the order defined in `OrderInitGenesis`. Returns an `abci.ResponseInitChain` to the underlying consensus engine, which can contain validator updates.
 * `ExportGenesis(ctx context.Context, cdc codec.JSONCodec)`: Calls the [`ExportGenesis`](./08-genesis.md#exportgenesis) function of each module, in the order defined in `OrderExportGenesis`. The export constructs a genesis file from a previously existing state, and is mainly used when a hard-fork upgrade of the chain is required.

docs/docs/core/08-events.md

@@ -96,14 +96,7 @@ ctx.EventManager().EmitEvent(
 )
 ```
 
-Module's `handler` function should also set a new `EventManager` to the `context` to isolate emitted Events per `message`:
+Where the `EventManager` is accessed via the [`Context`](./02-context.md).
-
-```go
-func NewHandler(keeper Keeper) sdk.Handler {
-    return func(ctx context.Context, msg sdk.Msg) (*sdk.Result, error) {
-        ctx = ctx.WithEventManager(sdk.NewEventManager())
-        switch msg := msg.(type) {
-```
 
 See the [`Msg` services](../building-modules/03-msg-services.md) concept doc for a more detailed
 view on how to typically implement Events and use the `EventManager` in modules.

server/mock/app.go

@@ -66,7 +66,7 @@ func NewApp(rootDir string, logger log.Logger) (servertypes.ABCI, error) {
 
 // KVStoreHandler is a simple handler that takes KVStoreTx and writes
 // them to the db.
-func KVStoreHandler(storeKey storetypes.StoreKey) sdk.Handler {
+func KVStoreHandler(storeKey storetypes.StoreKey) bam.MsgServiceHandler {
 	return func(ctx sdk.Context, msg sdk.Msg) (*sdk.Result, error) {
 		dTx, ok := msg.(*KVStoreTx)
 		if !ok {

types/handler.go

@@ -1,8 +1,5 @@
 package types
 
-// Handler defines the core of the state transition function of an application.
-type Handler func(ctx Context, msg Msg) (*Result, error)
-
 // AnteHandler authenticates transactions, before their internal messages are handled.
 // If newCtx.IsZero(), ctx is used instead.
 type AnteHandler func(ctx Context, tx Tx, simulate bool) (newCtx Context, err error)