feat: Allow app developers to override default appConfig template (#9550

)

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## Description

Closes: #5540

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---

### Author Checklist

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- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [x] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
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- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

docs/core/cli.md

@@ -60,7 +60,13 @@ The root command (called `rootCmd`) is what the user first types into the comman
 
 Next is an example `rootCmd` function from the `simapp` application. It instantiates the root command, adds a [_persistent_ flag](#flags) and `PreRun` function to be run before every execution, and adds all of the necessary subcommands.
 
-+++ https://github.com/cosmos/cosmos-sdk/blob/v0.40.0/simapp/simd/cmd/root.go#L37-L93
++++ https://github.com/cosmos/cosmos-sdk/blob/4eea4cafd3b8b1c2cd493886db524500c9dd745c/simapp/simd/cmd/root.go#L37-L150
+
+`rootCmd` has a function called `initAppConfig()` which is useful for setting the application's custom configs.
+By default app uses Tendermint app config template from SDK, which can be over-written via `initAppConfig()`.
+Here's an example code to override default `appConfig` and `app.toml` template.
+
++++ https://github.com/cosmos/cosmos-sdk/blob/4eea4cafd3b8b1c2cd493886db524500c9dd745c/simapp/simd/cmd/root.go#L84-L117
 
 The root-level `status` and `keys` subcommands are common across most applications and do not interact with application state. The bulk of an application's functionality - what users can actually _do_ with it - is enabled by its `tx` and `query` commands.
 

server/config/toml.go

@@ -8,7 +8,7 @@ import (
 	tmos "github.com/tendermint/tendermint/libs/os"
 )
 
-const defaultConfigTemplate = `# This is a TOML config file.
+const DefaultConfigTemplate = `# This is a TOML config file.
 # For more information, see https://github.com/toml-lang/toml
 
 ###############################################################################
@@ -210,7 +210,7 @@ func init() {
 
 	tmpl := template.New("appConfigFileTemplate")
 
-	if configTemplate, err = tmpl.Parse(defaultConfigTemplate); err != nil {
+	if configTemplate, err = tmpl.Parse(DefaultConfigTemplate); err != nil {
 		panic(err)
 	}
 }
@@ -224,9 +224,21 @@ func ParseConfig(v *viper.Viper) (*Config, error) {
 	return conf, err
 }
 
+// SetConfigTemplate sets the custom app config template for
+// the application
+func SetConfigTemplate(customTemplate string) {
+	var err error
+
+	tmpl := template.New("appConfigFileTemplate")
+
+	if configTemplate, err = tmpl.Parse(customTemplate); err != nil {
+		panic(err)
+	}
+}
+
 // WriteConfigFile renders config using the template and writes it to
 // configFilePath.
-func WriteConfigFile(configFilePath string, config *Config) {
+func WriteConfigFile(configFilePath string, config interface{}) {
 	var buffer bytes.Buffer
 
 	if err := configTemplate.Execute(&buffer, config); err != nil {

server/doc.go

@@ -22,6 +22,9 @@ value called `rpc.laddr` would be read from an environmental variable called
 Running the `InterceptConfigsPreRunHandler` also reads `app.toml`
 and `config.toml` from the home directory under the `config` directory.
 If `config.toml` or `app.toml` do not exist then those files are created
-and populated with default values.
+and populated with default values. `InterceptConfigsPreRunHandler` takes
+two parameters to set/update a custom template to create custom `app.toml`.
+If these parameters are empty, the server then creates a default template
+provided by the SDK.
 */
 package server

server/util.go

@@ -99,10 +99,13 @@ func bindFlags(basename string, cmd *cobra.Command, v *viper.Viper) (err error)
 // application command. It will create a Viper literal and a default server
 // Context. The server Tendermint configuration will either be read and parsed
 // or created and saved to disk, where the server Context is updated to reflect
-// the Tendermint configuration. The Viper literal is used to read and parse
-// the application configuration. Command handlers can fetch the server Context
-// to get the Tendermint configuration or to get access to Viper.
-func InterceptConfigsPreRunHandler(cmd *cobra.Command) error {
+// the Tendermint configuration. It takes custom app config template and config
+// settings to create a custom Tendermint configuration. If the custom template
+// is empty, it uses default-template provided by the server. The Viper literal
+// is used to read and parse the application configuration. Command handlers can
+// fetch the server Context to get the Tendermint configuration or to get access
+// to Viper.
+func InterceptConfigsPreRunHandler(cmd *cobra.Command, customAppConfigTemplate string, customAppConfig interface{}) error {
 	serverCtx := NewDefaultContext()
 
 	// Get the executable name and configure the viper instance so that environmental
@@ -123,7 +126,7 @@ func InterceptConfigsPreRunHandler(cmd *cobra.Command) error {
 	serverCtx.Viper.AutomaticEnv()
 
 	// intercept configuration files, using both Viper instances separately
-	config, err := interceptConfigs(serverCtx.Viper)
+	config, err := interceptConfigs(serverCtx.Viper, customAppConfigTemplate, customAppConfig)
 	if err != nil {
 		return err
 	}
@@ -181,7 +184,7 @@ func SetCmdServerContext(cmd *cobra.Command, serverCtx *Context) error {
 // configuration file. The Tendermint configuration file is parsed given a root
 // Viper object, whereas the application is parsed with the private package-aware
 // viperCfg object.
-func interceptConfigs(rootViper *viper.Viper) (*tmcfg.Config, error) {
+func interceptConfigs(rootViper *viper.Viper, customAppTemplate string, customConfig interface{}) (*tmcfg.Config, error) {
 	rootDir := rootViper.GetString(flags.FlagHome)
 	configPath := filepath.Join(rootDir, "config")
 	tmCfgFile := filepath.Join(configPath, "config.toml")
@@ -226,12 +229,22 @@ func interceptConfigs(rootViper *viper.Viper) (*tmcfg.Config, error) {
 
 	appCfgFilePath := filepath.Join(configPath, "app.toml")
 	if _, err := os.Stat(appCfgFilePath); os.IsNotExist(err) {
-		appConf, err := config.ParseConfig(rootViper)
-		if err != nil {
-			return nil, fmt.Errorf("failed to parse %s: %w", appCfgFilePath, err)
-		}
+		if customAppTemplate != "" {
+			config.SetConfigTemplate(customAppTemplate)
+
+			if err = rootViper.Unmarshal(&customConfig); err != nil {
+				return nil, fmt.Errorf("failed to parse %s: %w", appCfgFilePath, err)
+			}
 
-		config.WriteConfigFile(appCfgFilePath, appConf)
+			config.WriteConfigFile(appCfgFilePath, customConfig)
+		} else {
+			appConf, err := config.ParseConfig(rootViper)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse %s: %w", appCfgFilePath, err)
+			}
+
+			config.WriteConfigFile(appCfgFilePath, appConf)
+		}
 	}
 
 	rootViper.SetConfigType("toml")

server/util_test.go

@@ -20,7 +20,7 @@ var CancelledInPreRun = errors.New("Canelled in prerun")
 // Used in each test to run the function under test via Cobra
 // but to always halt the command
 func preRunETestImpl(cmd *cobra.Command, args []string) error {
-	err := InterceptConfigsPreRunHandler(cmd)
+	err := InterceptConfigsPreRunHandler(cmd, "", nil)
 	if err != nil {
 		return err
 	}

simapp/simd/cmd/root.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 
+	serverconfig "github.com/cosmos/cosmos-sdk/server/config"
 	"github.com/spf13/cast"
 	"github.com/spf13/cobra"
 	tmcli "github.com/tendermint/tendermint/libs/cli"
@@ -14,7 +15,7 @@ import (
 
 	"github.com/cosmos/cosmos-sdk/baseapp"
 	"github.com/cosmos/cosmos-sdk/client"
-	config "github.com/cosmos/cosmos-sdk/client/config"
+	"github.com/cosmos/cosmos-sdk/client/config"
 	"github.com/cosmos/cosmos-sdk/client/debug"
 	"github.com/cosmos/cosmos-sdk/client/flags"
 	"github.com/cosmos/cosmos-sdk/client/keys"
@@ -66,7 +67,9 @@ func NewRootCmd() (*cobra.Command, params.EncodingConfig) {
 				return err
 			}
 
-			return server.InterceptConfigsPreRunHandler(cmd)
+			customAppTemplate, customAppConfig := initAppConfig()
+
+			return server.InterceptConfigsPreRunHandler(cmd, customAppTemplate, customAppConfig)
 		},
 	}
 
@@ -75,6 +78,45 @@ func NewRootCmd() (*cobra.Command, params.EncodingConfig) {
 	return rootCmd, encodingConfig
 }
 
+// initAppConfig helps to override default appConfig template and configs.
+// return "", nil if no custom configuration is required for the application.
+func initAppConfig() (string, interface{}) {
+	// The following code snippet is just for reference.
+
+	// WASMConfig defines configuration for the wasm module.
+	type WASMConfig struct {
+		// This is the maximum sdk gas (wasm and storage) that we allow for any x/wasm "smart" queries
+		QueryGasLimit uint64 `mapstructure:"query_gas_limit"`
+
+		// Address defines the gRPC-web server to listen on
+		LruSize uint64 `mapstructure:"lru_size"`
+	}
+
+	type CustomAppConfig struct {
+		serverconfig.Config
+
+		WASM WASMConfig `mapstructure:"wasm"`
+	}
+
+	customAppConfig := CustomAppConfig{
+		Config: *serverconfig.DefaultConfig(),
+		WASM: WASMConfig{
+			LruSize:       1,
+			QueryGasLimit: 300000,
+		},
+	}
+
+	customAppTemplate := serverconfig.DefaultConfigTemplate + `
+[wasm]
+# This is the maximum sdk gas (wasm and storage) that we allow for any x/wasm "smart" queries
+query_gas_limit = 300000
+# This is the number of wasm vm instances we keep cached in memory for speed-up
+# Warning: this is currently unstable and may lead to crashes, best to keep for 0 unless testing locally
+lru_size = 0`
+
+	return customAppTemplate, customAppConfig
+}
+
 func initRootCmd(rootCmd *cobra.Command, encodingConfig params.EncodingConfig) {
 	cfg := sdk.GetConfig()
 	cfg.Seal()