error-messages

# Error Message Style Guide This guide establishes the standard format for validation error messages in the gh-aw codebase. All validation errors should be clear, actionable, and include examples. ## Error Message Template ``` [what's wrong]. [what's expected]. [example of correct usage] ``` Each error message should answer three questions: 1. **What's wrong?** - Clearly state the validation error 2. **What's expected?** - Explain the valid format or values 3. **How to fix it?** - Provide a concrete example of correct usage ## Good Examples These examples follow the template and provide actionable guidance: ### Time Delta Validation (from time_delta.go) ```go return nil, fmt.Errorf("invalid time delta format: +%s. Expected format like +25h, +3d, +1w, +1mo, +1d12h30m", deltaStr) ``` ✅ **Why it's good:** - Clearly identifies the invalid input - Lists multiple valid format examples - Shows combined formats (+1d12h30m) ### Type Validation with Example ```go return "", fmt.Errorf("manual-approval value must be a string, got %T. Example: manual-approval: \"production\"", val) ``` ✅ **Why it's good:** - Shows actual type received (%T) - Provides concrete YAML example - Uses proper YAML syntax with quotes ### Enum Validation with Options ```go return fmt.Errorf("invalid engine: %s. Valid engines are: copilot, claude, codex, custom. Example: engine: copilot", engineID) ``` ✅ **Why it's good:** - Lists all valid options - Provides simplest example - Uses consistent formatting ### MCP Configuration ```go return fmt.Errorf("tool '%s' mcp configuration must specify either 'command' or 'container'. Example:\ntools:\n %s:\n command: \"npx @my/tool\"", toolName, toolName) ``` ✅ **Why it's good:** - Explains mutual exclusivity - Shows realistic tool name - Formats multi-line YAML example ## Bad Examples These examples lack clarity or actionable guidance: ### Too Vague ```go return fmt.Errorf("invalid format") ``` ❌ **Problems:** - Doesn't specify what format is invalid - Doesn't explain expected format - No example provided ### Missing Example ```go return fmt.Errorf("manual-approval value must be a string") ``` ❌ **Problems:** - States requirement but no example - User doesn't know proper YAML syntax - Could be clearer about type received ### Incomplete Information ```go return fmt.Errorf("invalid engine: %s", engineID) ``` ❌ **Problems:** - Doesn't list valid options - No guidance on fixing the error - User must search documentation ## When to Include Examples Always include examples for: 1. **Format/Syntax Errors** - Show the correct syntax ```go fmt.Errorf("invalid date format. Expected: YYYY-MM-DD HH:MM:SS. Example: 2024-01-15 14:30:00") ``` 2. **Enum/Choice Fields** - List all valid options ```go fmt.Errorf("invalid permission level: %s. Valid levels: read, write, none. Example: permissions:\n contents: read", level) ``` 3. **Type Mismatches** - Show expected type and example ```go fmt.Errorf("timeout-minutes must be an integer, got %T. Example: timeout-minutes: 10", value) ``` 4. **Complex Configurations** - Provide complete valid example ```go fmt.Errorf("invalid MCP server config. Example:\nmcp-servers:\n my-server:\n command: \"node\"\n args: [\"server.js\"]") ``` ## When Examples May Be Optional Examples can be omitted when: 1. **Error is from wrapped error** - When wrapping another error with context ```go return fmt.Errorf("failed to parse configuration: %w", err) ``` 2. **Error is self-explanatory with clear context** ```go return fmt.Errorf("duplicate unit '%s' in time delta: +%s", unit, deltaStr) ``` 3. **Error points to specific documentation** ```go return fmt.Errorf("unsupported feature. See https://docs.example.com/features") ``` ## Formatting Guidelines ### Use Type Verbs for Dynamic Content - `%s` - strings - `%d` - integers - `%T` - type of value - `%v` - general value - `%w` - wrapped errors ### Multi-line Examples For YAML configuration examples spanning multiple lines: ```go fmt.Errorf("invalid config. Example:\ntools:\n github:\n mode: \"remote\"") ``` ### Quoting in Examples Use proper YAML syntax in examples: ```go // Good - shows quotes when needed fmt.Errorf("Example: name: \"my-workflow\"") // Good - shows no quotes for simple values fmt.Errorf("Example: timeout-minutes: 10") ``` ### Consistent Terminology Use the same field names as in YAML: ```go // Good - matches YAML field name fmt.Errorf("timeout-minutes must be positive") // Bad - uses different name fmt.Errorf("timeout must be positive") ``` ## Error Message Testing All improved error messages should have corresponding tests: ```go func TestErrorMessageQuality(t *testing.T) { err := validateSomething(invalidInput) require.Error(t, err) // Error should explain what's wrong assert.Contains(t, err.Error(), "invalid") // Error should include expected format or values assert.Contains(t, err.Error(), "Expected") // Error should include example assert.Contains(t, err.Error(), "Example:") } ``` ## Migration Strategy When improving existing error messages: 1. **Identify the error** - Find validation error that lacks clarity 2. **Analyze context** - Understand what's being validated 3. **Apply template** - Add what's wrong + expected + example 4. **Add tests** - Verify error message content 5. **Update comments** - Document the validation logic ## Examples by Category ### Format Validation ```go // Time deltas fmt.Errorf("invalid time delta format: +%s. Expected format like +25h, +3d, +1w, +1mo, +1d12h30m", input) // Dates fmt.Errorf("invalid date format: %s. Expected: YYYY-MM-DD or relative like -1w. Example: 2024-01-15 or -7d", input) // URLs fmt.Errorf("invalid URL format: %s. Expected: https:// URL. Example: https://api.example.com", input) ``` ### Type Validation ```go // Boolean expected fmt.Errorf("read-only must be a boolean, got %T. Example: read-only: true", value) // String expected fmt.Errorf("workflow name must be a string, got %T. Example: name: \"my-workflow\"", value) // Object expected fmt.Errorf("permissions must be an object, got %T. Example: permissions:\n contents: read", value) ``` ### Choice/Enum Validation ```go // Engine selection fmt.Errorf("invalid engine: %s. Valid engines: copilot, claude, codex, custom. Example: engine: copilot", id) // Permission levels fmt.Errorf("invalid permission level: %s. Valid levels: read, write, none. Example: contents: read", level) // Tool modes fmt.Errorf("invalid mode: %s. Valid modes: local, remote. Example: mode: \"remote\"", mode) ``` ### Configuration Validation ```go // Missing required field fmt.Errorf("tool '%s' missing required 'command' field. Example:\ntools:\n %s:\n command: \"node server.js\"", name, name) // Mutually exclusive fields fmt.Errorf("cannot specify both 'command' and 'container'. Choose one. Example: command: \"node server.js\"") // Invalid combination fmt.Errorf("http MCP servers cannot use 'container' field. Example:\ntools:\n my-http:\n type: http\n url: \"https://api.example.com\"") ``` ## References - **Excellent example to follow**: `pkg/workflow/time_delta.go` - **Pattern inspiration**: Go standard library error messages - **Testing examples**: `pkg/workflow/*_test.go` ## Tools When writing error messages, consider: - The user's perspective (what do they need to fix it?) - The context (where in the workflow is the error?) - The documentation (should we reference specific docs?) - The complexity (is multi-line example needed?) --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/github) — claim your Tome and manage your conversions. <!-- tomevault:4.0:skill_md:2026-04-11 -->