add-wshcmd

name	add-wshcmd
description	Guide for adding new wsh commands to Pengu. Use when implementing new CLI commands, adding command-line functionality, or extending the wsh command interface.

Adding a New wsh Command to Pengu

This guide explains how to add a new command to the wsh CLI tool.

wsh Command System Overview

Pengu's wsh command provides CLI access to Pengu features. The system uses:

1. Cobra Framework - CLI command structure and parsing
2. Command Files - Individual command implementations in cmd/wsh/cmd/wshcmd-*.go
3. RPC Client - Communication with Pengu backend via RpcClient
4. Activity Tracking - Telemetry for command usage analytics
5. Documentation - User-facing docs in docs/docs/wsh-reference.mdx

Commands are registered in their init() functions and execute through the Cobra framework.

Step-by-Step Guide

Step 1: Create Command File

Create a new file in cmd/wsh/cmd/ named wshcmd-[commandname].go:

// Copyright 2025, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package cmd

import (
    "fmt"

    "github.com/spf13/cobra"
    "github.com/pengudev/pengu/pkg/wshrpc"
    "github.com/pengudev/pengu/pkg/wshrpc/wshclient"
)

var myCommandCmd = &cobra.Command{
    Use:   "mycommand [args]",
    Short: "Brief description of what this command does",
    Long: `Detailed description of the command.
Can include multiple lines and examples of usage.`,
    RunE:                  myCommandRun,
    PreRunE:               preRunSetupRpcClient,  // Include if command needs RPC
    DisableFlagsInUseLine: true,
}

// Flag variables
var (
    myCommandFlagExample string
    myCommandFlagVerbose bool
)

func init() {
    // Add command to root
    rootCmd.AddCommand(myCommandCmd)
    
    // Define flags
    myCommandCmd.Flags().StringVarP(&myCommandFlagExample, "example", "e", "", "example flag description")
    myCommandCmd.Flags().BoolVarP(&myCommandFlagVerbose, "verbose", "v", false, "enable verbose output")
}

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    // Always track activity for telemetry
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    // Validate arguments
    if len(args) == 0 {
        OutputHelpMessage(cmd)
        return fmt.Errorf("requires at least one argument")
    }
    
    // Command implementation
    fmt.Printf("Command executed successfully\n")
    return nil
}

File Naming Convention:

• Use wshcmd-[commandname].go format
• Use lowercase, hyphenated names for multi-word commands
• Examples: wshcmd-getvar.go, wshcmd-setmeta.go, wshcmd-ai.go

Step 2: Command Structure

Basic Command Structure

var myCommandCmd = &cobra.Command{
    Use:   "mycommand [required] [optional...]",
    Short: "One-line description (shown in help)",
    Long:  `Detailed multi-line description`,
    
    // Argument validation
    Args:    cobra.MinimumNArgs(1),  // Or cobra.ExactArgs(1), cobra.NoArgs, etc.
    
    // Execution function
    RunE:    myCommandRun,
    
    // Pre-execution setup (if needed)
    PreRunE: preRunSetupRpcClient,  // Sets up RPC client for backend communication
    
    // Example usage (optional)
    Example: "  wsh mycommand foo\n  wsh mycommand --flag bar",
    
    // Disable flag notation in usage line
    DisableFlagsInUseLine: true,
}

Key Fields:

• Use: Command name and argument pattern
• Short: Brief description for command list
• Long: Detailed description shown in help
• Args: Argument validator (optional)
• RunE: Main execution function (returns error)
• PreRunE: Setup function that runs before RunE
• Example: Usage examples (optional)
• DisableFlagsInUseLine: Clean up help display

When to Use PreRunE

Include PreRunE: preRunSetupRpcClient if your command:

• Communicates with the Pengu backend
• Needs access to RpcClient
• Requires JWT authentication (PENGU_JWT env var)
• Makes RPC calls via wshclient.*Command() functions

Don't include PreRunE for commands that:

• Only manipulate local state
• Don't need backend communication
• Are purely informational/local operations

Step 3: Implement Command Logic

Command Function Pattern

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    // Step 1: Always track activity (for telemetry)
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    // Step 2: Validate arguments and flags
    if len(args) != 1 {
        OutputHelpMessage(cmd)
        return fmt.Errorf("requires exactly one argument")
    }
    
    // Step 3: Parse/prepare data
    targetArg := args[0]
    
    // Step 4: Make RPC call if needed
    result, err := wshclient.SomeCommand(RpcClient, wshrpc.CommandSomeData{
        Field: targetArg,
    }, &wshrpc.RpcOpts{Timeout: 2000})
    if err != nil {
        return fmt.Errorf("executing command: %w", err)
    }
    
    // Step 5: Output results
    fmt.Printf("Result: %s\n", result)
    return nil
}

Important Patterns:

1. Activity Tracking: Always include deferred sendActivity() call

   defer func() {
       sendActivity("commandname", rtnErr == nil)
   }()
   

2. Error Handling: Return errors, don't call os.Exit()

   if err != nil {
       return fmt.Errorf("context: %w", err)
   }
   

3. Output: Use standard fmt package for output

   fmt.Printf("Success message\n")
   fmt.Fprintf(os.Stderr, "Error message\n")
   

4. Help Messages: Show help when arguments are invalid

   if len(args) == 0 {
       OutputHelpMessage(cmd)
       return fmt.Errorf("requires arguments")
   }
   

5. Exit Codes: Set custom exit code via WshExitCode

   if notFound {
       WshExitCode = 1
       return nil  // Don't return error, just set exit code
   }
   

Step 4: Define Flags

Add flags in the init() function:

var (
    // Declare flag variables at package level
    myCommandFlagString string
    myCommandFlagBool   bool
    myCommandFlagInt    int
)

func init() {
    rootCmd.AddCommand(myCommandCmd)
    
    // String flag with short version
    myCommandCmd.Flags().StringVarP(&myCommandFlagString, "name", "n", "default", "description")
    
    // Boolean flag
    myCommandCmd.Flags().BoolVarP(&myCommandFlagBool, "verbose", "v", false, "enable verbose")
    
    // Integer flag
    myCommandCmd.Flags().IntVar(&myCommandFlagInt, "count", 10, "set count")
    
    // Flag without short version
    myCommandCmd.Flags().StringVar(&myCommandFlagString, "longname", "", "description")
}

Flag Types:

• StringVar/StringVarP - String values
• BoolVar/BoolVarP - Boolean flags
• IntVar/IntVarP - Integer values
• The P suffix versions include a short flag name

Flag Naming:

• Use camelCase for variable names: myCommandFlagName
• Use kebab-case for flag names: --flag-name
• Prefix variable names with command name for clarity

Step 5: Working with Block Arguments

Many commands operate on blocks. Use the standard block resolution pattern:

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    // Resolve block using the -b/--block flag
    fullORef, err := resolveBlockArg()
    if err != nil {
        return err
    }
    
    // Use the blockid in RPC call
    err = wshclient.SomeCommand(RpcClient, wshrpc.CommandSomeData{
        BlockId: fullORef.OID,
    }, &wshrpc.RpcOpts{Timeout: 2000})
    if err != nil {
        return fmt.Errorf("command failed: %w", err)
    }
    
    return nil
}

Block Resolution:

• The -b/--block flag is defined globally in wshcmd-root.go
• resolveBlockArg() resolves the block argument to a full ORef
• Supports: this, tab, full UUIDs, 8-char prefixes, block numbers
• Default is "this" (current block)

Alternative: Manual Block Resolution

// Get tab ID from environment
tabId := os.Getenv("PENGU_TABID")
if tabId == "" {
    return fmt.Errorf("PENGU_TABID not set")
}

// Create route for tab-level operations
route := wshutil.MakeTabRouteId(tabId)

// Use route in RPC call
err := wshclient.SomeCommand(RpcClient, commandData, &wshrpc.RpcOpts{
    Route:   route,
    Timeout: 2000,
})

Step 6: Making RPC Calls

Use the wshclient package to make RPC calls:

import (
    "github.com/pengudev/pengu/pkg/wshrpc"
    "github.com/pengudev/pengu/pkg/wshrpc/wshclient"
)

// Simple RPC call
result, err := wshclient.GetMetaCommand(RpcClient, wshrpc.CommandGetMetaData{
    ORef: *fullORef,
}, &wshrpc.RpcOpts{Timeout: 2000})
if err != nil {
    return fmt.Errorf("getting metadata: %w", err)
}

// RPC call with routing
err := wshclient.SetMetaCommand(RpcClient, wshrpc.CommandSetMetaData{
    ORef: *fullORef,
    Meta: metaMap,
}, &wshrpc.RpcOpts{
    Route:   route,
    Timeout: 5000,
})
if err != nil {
    return fmt.Errorf("setting metadata: %w", err)
}

RPC Options:

• Timeout: Request timeout in milliseconds (typically 2000-5000)
• Route: Route ID for targeting specific components
• Available routes: wshutil.ControlRoute, wshutil.MakeTabRouteId(tabId)

Step 7: Add Documentation

Add your command to docs/docs/wsh-reference.mdx:

## mycommand

Brief description of what the command does.

```sh
wsh mycommand [args] [flags]
```

Detailed explanation of the command's purpose and behavior.

Flags:
- `-n, --name <value>` - description of this flag
- `-v, --verbose` - enable verbose output
- `-b, --block <blockid>` - specify target block (default: current block)

Examples:

```sh
# Basic usage
wsh mycommand arg1

# With flags
wsh mycommand --name value arg1

# With block targeting
wsh mycommand -b 2 arg1

# Complex example
wsh mycommand -v --name "example" arg1 arg2
```

Additional notes, tips, or warnings about the command.

---

Documentation Guidelines:

• Place in alphabetical order with other commands
• Include command signature with argument pattern
• List all flags with short and long versions
• Provide practical examples (at least 3-5)
• Explain common use cases and patterns
• Add tips or warnings if relevant
• Use --- separator between commands

Step 8: Test Your Command

Build and test the command:

# Build wsh
task build:wsh

# Or build everything
task build

# Test the command
./bin/wsh/wsh mycommand --help
./bin/wsh/wsh mycommand arg1 arg2

Testing Checklist:

• Help message displays correctly
• Required arguments validated
• Flags work as expected
• Error messages are clear
• Success cases work correctly
• RPC calls complete successfully
• Output is formatted correctly

Complete Examples

Example 1: Simple Command with No RPC

Use case: A command that prints Pengu version info

Command File (cmd/wsh/cmd/wshcmd-version.go)

// Copyright 2025, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package cmd

import (
    "github.com/spf13/cobra"
    "github.com/pengudev/pengu/pkg/wavebase"
)

var versionCmd = &cobra.Command{
    Use:   "version",
    Short: "Print Pengu version",
    RunE:  versionRun,
}

func init() {
    rootCmd.AddCommand(versionCmd)
}

func versionRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("version", rtnErr == nil)
    }()
    
    fmt.Printf("Pengu %s\n", wavebase.PenguVersion)
    return nil
}

Documentation

## version

Print the current Pengu version.

```sh
wsh version
```

Examples:

```sh
# Print version
wsh version
```

Example 2: Command with Flags and RPC

Use case: A command to update block title

Command File (cmd/wsh/cmd/wshcmd-settitle.go)

// Copyright 2025, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package cmd

import (
    "fmt"

    "github.com/spf13/cobra"
    "github.com/pengudev/pengu/pkg/wshrpc"
    "github.com/pengudev/pengu/pkg/wshrpc/wshclient"
)

var setTitleCmd = &cobra.Command{
    Use:   "settitle [title]",
    Short: "Set block title",
    Long:  `Set the title for the current or specified block.`,
    Args:  cobra.ExactArgs(1),
    RunE:  setTitleRun,
    PreRunE: preRunSetupRpcClient,
    DisableFlagsInUseLine: true,
}

var setTitleIcon string

func init() {
    rootCmd.AddCommand(setTitleCmd)
    setTitleCmd.Flags().StringVarP(&setTitleIcon, "icon", "i", "", "set block icon")
}

func setTitleRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("settitle", rtnErr == nil)
    }()
    
    title := args[0]
    
    // Resolve block
    fullORef, err := resolveBlockArg()
    if err != nil {
        return err
    }
    
    // Build metadata map
    meta := make(map[string]interface{})
    meta["title"] = title
    if setTitleIcon != "" {
        meta["icon"] = setTitleIcon
    }
    
    // Make RPC call
    err = wshclient.SetMetaCommand(RpcClient, wshrpc.CommandSetMetaData{
        ORef: *fullORef,
        Meta: meta,
    }, &wshrpc.RpcOpts{Timeout: 2000})
    if err != nil {
        return fmt.Errorf("setting title: %w", err)
    }
    
    fmt.Printf("title updated\n")
    return nil
}

Documentation

## settitle

Set the title for a block.

```sh
wsh settitle [title]
```

Update the display title for the current or specified block. Optionally set an icon as well.

Flags:
- `-i, --icon <icon>` - set block icon along with title
- `-b, --block <blockid>` - specify target block (default: current block)

Examples:

```sh
# Set title for current block
wsh settitle "My Terminal"

# Set title and icon
wsh settitle --icon "terminal" "Development Shell"

# Set title for specific block
wsh settitle -b 2 "Build Output"
```

Example 3: Subcommands

Use case: Command with multiple subcommands (like wsh conn)

Command File (cmd/wsh/cmd/wshcmd-mygroup.go)

// Copyright 2025, Command Line Inc.
// SPDX-License-Identifier: Apache-2.0

package cmd

import (
    "fmt"

    "github.com/spf13/cobra"
    "github.com/pengudev/pengu/pkg/wshrpc"
    "github.com/pengudev/pengu/pkg/wshrpc/wshclient"
)

var myGroupCmd = &cobra.Command{
    Use:   "mygroup",
    Short: "Manage something",
}

var myGroupListCmd = &cobra.Command{
    Use:   "list",
    Short: "List items",
    RunE:  myGroupListRun,
    PreRunE: preRunSetupRpcClient,
}

var myGroupAddCmd = &cobra.Command{
    Use:   "add [name]",
    Short: "Add an item",
    Args:  cobra.ExactArgs(1),
    RunE:  myGroupAddRun,
    PreRunE: preRunSetupRpcClient,
}

func init() {
    // Add parent command
    rootCmd.AddCommand(myGroupCmd)
    
    // Add subcommands
    myGroupCmd.AddCommand(myGroupListCmd)
    myGroupCmd.AddCommand(myGroupAddCmd)
}

func myGroupListRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mygroup:list", rtnErr == nil)
    }()
    
    // Implementation
    fmt.Printf("Listing items...\n")
    return nil
}

func myGroupAddRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mygroup:add", rtnErr == nil)
    }()
    
    name := args[0]
    fmt.Printf("Adding item: %s\n", name)
    return nil
}

Documentation

## mygroup

Manage something with subcommands.

### list

List all items.

```sh
wsh mygroup list
```

### add

Add a new item.

```sh
wsh mygroup add [name]
```

Examples:

```sh
# List items
wsh mygroup list

# Add an item
wsh mygroup add "new-item"
```

Common Patterns

Reading from Stdin

import "io"

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    // Check if reading from stdin (using "-" convention)
    var data []byte
    var err error
    
    if len(args) > 0 && args[0] == "-" {
        data, err = io.ReadAll(os.Stdin)
        if err != nil {
            return fmt.Errorf("reading stdin: %w", err)
        }
    } else {
        // Read from file or other source
        data, err = os.ReadFile(args[0])
        if err != nil {
            return fmt.Errorf("reading file: %w", err)
        }
    }
    
    // Process data
    fmt.Printf("Read %d bytes\n", len(data))
    return nil
}

JSON File Input

import (
    "encoding/json"
    "io"
)

func loadJSONFile(filepath string) (map[string]interface{}, error) {
    var data []byte
    var err error
    
    if filepath == "-" {
        data, err = io.ReadAll(os.Stdin)
        if err != nil {
            return nil, fmt.Errorf("reading stdin: %w", err)
        }
    } else {
        data, err = os.ReadFile(filepath)
        if err != nil {
            return nil, fmt.Errorf("reading file: %w", err)
        }
    }
    
    var result map[string]interface{}
    if err := json.Unmarshal(data, &result); err != nil {
        return nil, fmt.Errorf("parsing JSON: %w", err)
    }
    
    return result, nil
}

Conditional Output (TTY Detection)

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    isTty := getIsTty()
    
    // Output value
    fmt.Printf("%s", value)
    
    // Add newline only if TTY (for better piping experience)
    if isTty {
        fmt.Printf("\n")
    }
    
    return nil
}

Environment Variable Access

func myCommandRun(cmd *cobra.Command, args []string) (rtnErr error) {
    defer func() {
        sendActivity("mycommand", rtnErr == nil)
    }()
    
    // Get block ID from environment
    blockId := os.Getenv("PENGU_BLOCKID")
    if blockId == "" {
        return fmt.Errorf("PENGU_BLOCKID not set")
    }
    
    // Get tab ID from environment
    tabId := os.Getenv("PENGU_TABID")
    if tabId == "" {
        return fmt.Errorf("PENGU_TABID not set")
    }
    
    fmt.Printf("Block: %s, Tab: %s\n", blockId, tabId)
    return nil
}

Best Practices

Command Design

1. Single Responsibility: Each command should do one thing well
2. Composable: Design commands to work with pipes and other commands
3. Consistent: Follow existing wsh command patterns and conventions
4. Documented: Provide clear help text and examples

Error Handling

1. Context: Wrap errors with context using fmt.Errorf("context: %w", err)
2. User-Friendly: Make error messages clear and actionable
3. No Panics: Return errors instead of calling os.Exit() or panic()
4. Exit Codes: Use WshExitCode for custom exit codes

Output

1. Structured: Use consistent formatting for output
2. Quiet by Default: Only output what's necessary
3. Verbose Flag: Optionally provide -v for detailed output
4. Stderr for Errors: Use fmt.Fprintf(os.Stderr, ...) for error messages

Flags

1. Short Versions: Provide -x short versions for common flags
2. Sensible Defaults: Choose defaults that work for most users
3. Boolean Flags: Use for on/off options
4. String Flags: Use for values that need user input

RPC Calls

1. Timeouts: Always specify reasonable timeouts
2. Error Context: Wrap RPC errors with operation context
3. Retries: Don't retry automatically; let user retry command
4. Routes: Use appropriate routes for different operations

Common Pitfalls

1. Forgetting Activity Tracking

Problem: Command usage not tracked in telemetry

Solution: Always include deferred sendActivity() call:

defer func() {
    sendActivity("commandname", rtnErr == nil)
}()

2. Using os.Exit() Instead of Returning Error

Problem: Breaks defer statements and cleanup

Solution: Return errors from RunE function:

// Bad
if err != nil {
    fmt.Fprintf(os.Stderr, "error: %v\n", err)
    os.Exit(1)
}

// Good
if err != nil {
    return fmt.Errorf("operation failed: %w", err)
}

3. Not Validating Arguments

Problem: Command crashes with nil pointer or index out of range

Solution: Validate arguments early and show help:

if len(args) == 0 {
    OutputHelpMessage(cmd)
    return fmt.Errorf("requires at least one argument")
}

4. Forgetting to Add to init()

Problem: Command not available when running wsh

Solution: Always add command in init() function:

func init() {
    rootCmd.AddCommand(myCommandCmd)
}

5. Inconsistent Output

Problem: Inconsistent use of output methods

Solution: Use standard fmt package functions:

// For stdout
fmt.Printf("output\n")

// For stderr
fmt.Fprintf(os.Stderr, "error message\n")

Quick Reference Checklist

When adding a new wsh command:

• Create cmd/wsh/cmd/wshcmd-[commandname].go
• Define command struct with Use, Short, Long descriptions
• Add PreRunE: preRunSetupRpcClient if using RPC
• Implement command function with activity tracking
• Add command to rootCmd in init() function
• Define flags in init() function if needed
• Add documentation to docs/docs/wsh-reference.mdx
• Build and test: task build:wsh
• Test help: wsh [commandname] --help
• Test all flag combinations
• Test error cases

Related Files

• Root Command: cmd/wsh/cmd/wshcmd-root.go - Main command setup and utilities
• RPC Client: pkg/wshrpc/wshclient/ - Client functions for RPC calls
• RPC Types: pkg/wshrpc/wshrpctypes.go - RPC request/response data structures
• Documentation: docs/docs/wsh-reference.mdx - User-facing command reference
• Examples: cmd/wsh/cmd/wshcmd-*.go - Existing command implementations