feature/oh-my-zsh-completions (#289)

* shell completions for zsh

* after code review changes

* expose only postinstall.js script

* Replace _openspec "$@" with compdef in zsh-generator.ts to prevent execution during load

* Update test/commands/completion.test.ts

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* - Fix dispatcher to use $words instead of $line for subcommand routing
  - Add __complete endpoint with tab-separated output for safe parsing
  - Replace brittle awk parsing with __complete in completion helpers
  - Add uninstall confirmation prompt with --yes flag to skip
  - Prefer $ZSH env var for Oh My Zsh detection before dir check
  - Add fpath verification guidance for OMZ installations
  - Update cli-completion spec to document generate subcommand

* improve shell detection and installation handling

  - Return structured result from detectShell() with shell and detected name
  - Detect already-installed completions and skip reinstall
  - Add update detection with automatic backup of previous version
  - Add debug logging to silent catch blocks for diagnostics
  - Quote fpath directories to handle paths with spaces
  - Verify Oh My Zsh fpath configuration and add to .zshrc if needed
  - Show helpful error for detected but unsupported shells
  - Update all tests for new detection API

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: Tabish Bidiwale <[email protected]>

Author: 3 people

openspec/changes/archive/2025-11-06-add-shell-completions/design.md

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+# Add Shell Completions
+
+## Why
+
+OpenSpec CLI commands lack shell completion, forcing users to remember all commands, subcommands, flags, and change/spec IDs manually. This creates friction during daily use and slows developer workflows. Shell completions are a standard expectation for modern CLI tools and significantly improve user experience through:
+- Faster command discovery via tab completion
+- Reduced cognitive load by removing memorization requirements
+- Fewer typos through validated suggestions
+- Professional polish expected of production-grade tools
+
+## What Changes
+
+This change adds shell completion support for the OpenSpec CLI, starting with **Zsh (including Oh My Zsh)** and establishing a scalable architecture for future shells (bash, fish, PowerShell). The implementation provides:
+
+1. **New `openspec completion` command** with Zsh generation and installation/uninstallation capabilities
+2. **Native Zsh integration** that respects standard Zsh tab completion behavior (single-TAB menu navigation)
+3. **Dynamic completion providers** that discover active changes and specs from the current project
+4. **Plugin-based architecture** using TypeScript interfaces for easy extension to additional shells in future proposals
+5. **Installation automation** for Oh My Zsh (priority) and standard Zsh configurations
+6. **Context-aware suggestions** that only activate within OpenSpec-enabled projects
+
+The architecture emphasizes clean TypeScript patterns, composable generators, separation of concerns between shell-specific logic and shared completion data providers, and integration with native shell completion systems. Other shells (bash, fish, PowerShell) are architecturally documented but not implemented in this proposal—they will be added in follow-up changes.
+
+## Deltas
+
+### Delta: New CLI completion specification
+- **Spec:** cli-completion
+- **Operation:** ADDED
+- **Description:** Defines requirements for the new `openspec completion` command including generation, installation, and shell-specific behaviors for Oh My Zsh, bash, fish, and PowerShell.

openspec/changes/archive/2025-11-06-add-shell-completions/proposal.md

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+# CLI Completion Specification
+
+## Purpose
+
+The `openspec completion` command SHALL provide shell completion functionality for all OpenSpec CLI commands, flags, and dynamic values (change IDs, spec IDs), with support for Zsh (including Oh My Zsh) and a scalable architecture ready for future shells (bash, fish, PowerShell). The completion system SHALL integrate with Zsh's native completion behavior rather than attempting to customize the user experience.
+
+## ADDED Requirements
+
+### Requirement: Native Shell Behavior Integration
+
+The completion system SHALL respect and integrate with Zsh's native completion patterns and user interaction model.
+
+#### Scenario: Zsh native completion
+
+- **WHEN** generating Zsh completion scripts
+- **THEN** use Zsh completion system with `_arguments`, `_describe`, and `compadd`
+- **AND** completions SHALL trigger on single TAB (standard Zsh behavior)
+- **AND** display as an interactive menu that users navigate with TAB/arrow keys
+- **AND** support Oh My Zsh's enhanced menu styling automatically
+
+#### Scenario: No custom UX patterns
+
+- **WHEN** implementing Zsh completion
+- **THEN** do NOT attempt to customize completion trigger behavior
+- **AND** do NOT override Zsh-specific navigation patterns
+- **AND** ensure completions feel native to experienced Zsh users
+
+### Requirement: Command Structure
+
+The completion command SHALL follow a subcommand pattern for generating and managing completion scripts.
+
+#### Scenario: Available subcommands
+
+- **WHEN** user executes `openspec completion --help`
+- **THEN** display available subcommands:
+  - `zsh` - Generate Zsh completion script
+  - `install [shell]` - Install completion for Zsh (auto-detects or requires explicit shell)
+  - `uninstall [shell]` - Remove completion for Zsh (auto-detects or requires explicit shell)
+
+### Requirement: Shell Detection
+
+The completion system SHALL automatically detect the user's current shell environment.
+
+#### Scenario: Detecting Zsh from environment
+
+- **WHEN** no shell is explicitly specified
+- **THEN** read the `$SHELL` environment variable
+- **AND** extract the shell name from the path (e.g., `/bin/zsh` → `zsh`)
+- **AND** validate the shell is `zsh`
+- **AND** throw an error if the shell is not `zsh`, with message indicating only Zsh is currently supported
+
+#### Scenario: Non-Zsh shell detection
+
+- **WHEN** shell path indicates bash, fish, powershell, or other non-Zsh shell
+- **THEN** throw error: "Shell '<name>' is not supported yet. Currently supported: zsh"
+
+### Requirement: Completion Generation
+
+The completion command SHALL generate Zsh completion scripts on demand.
+
+#### Scenario: Generating Zsh completion
+
+- **WHEN** user executes `openspec completion zsh`
+- **THEN** output a complete Zsh completion script to stdout
+- **AND** include completions for all commands: init, list, show, validate, archive, view, update, change, spec, completion
+- **AND** include all command-specific flags and options
+- **AND** use Zsh's `_arguments` and `_describe` built-in functions
+- **AND** support dynamic completion for change and spec IDs
+
+### Requirement: Dynamic Completions
+
+The completion system SHALL provide context-aware dynamic completions for project-specific values.
+
+#### Scenario: Completing change IDs
+
+- **WHEN** completing arguments for commands that accept change names (show, validate, archive)
+- **THEN** discover active changes from `openspec/changes/` directory
+- **AND** exclude archived changes in `openspec/changes/archive/`
+- **AND** return change IDs as completion suggestions
+- **AND** only provide suggestions when inside an OpenSpec-enabled project
+
+#### Scenario: Completing spec IDs
+
+- **WHEN** completing arguments for commands that accept spec names (show, validate)
+- **THEN** discover specs from `openspec/specs/` directory
+- **AND** return spec IDs as completion suggestions
+- **AND** only provide suggestions when inside an OpenSpec-enabled project
+
+#### Scenario: Completion caching
+
+- **WHEN** dynamic completions are requested
+- **THEN** cache discovered change and spec IDs for 2 seconds
+- **AND** reuse cached values for subsequent requests within cache window
+- **AND** automatically refresh cache after expiration
+
+#### Scenario: Project detection
+
+- **WHEN** user requests completions outside an OpenSpec project
+- **THEN** skip dynamic change/spec ID completions
+- **AND** only suggest static commands and flags
+
+### Requirement: Installation Automation
+
+The completion command SHALL automatically install completion scripts into shell configuration files.
+
+#### Scenario: Installing for Oh My Zsh
+
+- **WHEN** user executes `openspec completion install zsh`
+- **THEN** detect if Oh My Zsh is installed by checking for `$ZSH` environment variable or `~/.oh-my-zsh/` directory
+- **AND** create custom completions directory at `~/.oh-my-zsh/custom/completions/` if it doesn't exist
+- **AND** write completion script to `~/.oh-my-zsh/custom/completions/_openspec`
+- **AND** ensure `~/.oh-my-zsh/custom/completions` is in `$fpath` by updating `~/.zshrc` if needed
+- **AND** display success message with instruction to run `exec zsh` or restart terminal
+
+#### Scenario: Installing for standard Zsh
+
+- **WHEN** user executes `openspec completion install zsh` and Oh My Zsh is not detected
+- **THEN** create completions directory at `~/.zsh/completions/` if it doesn't exist
+- **AND** write completion script to `~/.zsh/completions/_openspec`
+- **AND** add `fpath=(~/.zsh/completions $fpath)` to `~/.zshrc` if not already present
+- **AND** add `autoload -Uz compinit && compinit` to `~/.zshrc` if not already present
+- **AND** display success message with instruction to run `exec zsh` or restart terminal
+
+#### Scenario: Auto-detecting Zsh for installation
+
+- **WHEN** user executes `openspec completion install` without specifying a shell
+- **THEN** detect current shell using shell detection logic
+- **AND** install completion if detected shell is Zsh
+- **AND** throw error if detected shell is not Zsh
+- **AND** display which shell was detected
+
+#### Scenario: Already installed
+
+- **WHEN** completion is already installed for the target shell
+- **THEN** display message indicating completion is already installed
+- **AND** offer to reinstall/update by overwriting existing files
+- **AND** exit with code 0
+
+### Requirement: Uninstallation
+
+The completion command SHALL remove installed completion scripts and configuration.
+
+#### Scenario: Uninstalling Oh My Zsh completion
+
+- **WHEN** user executes `openspec completion uninstall zsh`
+- **THEN** remove `~/.oh-my-zsh/custom/completions/_openspec` if Oh My Zsh is detected
+- **AND** remove `~/.zsh/completions/_openspec` if standard Zsh setup is detected
+- **AND** optionally remove fpath modifications from `~/.zshrc` (with confirmation)
+- **AND** display success message
+
+#### Scenario: Auto-detecting Zsh for uninstallation
+
+- **WHEN** user executes `openspec completion uninstall` without specifying a shell
+- **THEN** detect current shell and uninstall completion if shell is Zsh
+- **AND** throw error if detected shell is not Zsh
+
+#### Scenario: Not installed
+
+- **WHEN** attempting to uninstall completion that isn't installed
+- **THEN** display message indicating completion is not installed
+- **AND** exit with code 0
+
+### Requirement: Architecture Patterns
+
+The completion implementation SHALL follow clean architecture principles with TypeScript best practices.
+
+#### Scenario: Shell-specific generators
+
+- **WHEN** implementing completion generators
+- **THEN** create `ZshCompletionGenerator` class for Zsh
+- **AND** implement a common `CompletionGenerator` interface with methods:
+  - `generate(): string` - Returns complete shell script
+  - `getInstallPath(): string` - Returns target installation path
+  - `getConfigFile(): string` - Returns shell configuration file path
+- **AND** design interface to be extensible for future shells (bash, fish, powershell)
+
+#### Scenario: Dynamic completion providers
+
+- **WHEN** implementing dynamic completions
+- **THEN** create a `CompletionProvider` class that encapsulates project discovery logic
+- **AND** implement methods:
+  - `getChangeIds(): Promise<string[]>` - Discovers active change IDs
+  - `getSpecIds(): Promise<string[]>` - Discovers spec IDs
+  - `isOpenSpecProject(): boolean` - Checks if current directory is OpenSpec-enabled
+- **AND** implement caching with 2-second TTL using class properties
+
+#### Scenario: Command registry
+
+- **WHEN** defining completable commands
+- **THEN** create a centralized `CommandDefinition` type with properties:
+  - `name: string` - Command name
+  - `description: string` - Help text
+  - `flags: FlagDefinition[]` - Available flags
+  - `acceptsChangeId: boolean` - Whether command takes change ID argument
+  - `acceptsSpecId: boolean` - Whether command takes spec ID argument
+  - `subcommands?: CommandDefinition[]` - Nested subcommands
+- **AND** export a `COMMAND_REGISTRY` constant with all command definitions
+- **AND** generators consume this registry to ensure consistency
+
+#### Scenario: Type-safe shell detection
+
+- **WHEN** implementing shell detection
+- **THEN** define a `SupportedShell` type as literal type: `'zsh'`
+- **AND** implement `detectShell()` function that returns 'zsh' or throws error
+- **AND** design type to be extensible (e.g., future: `'bash' | 'zsh' | 'fish' | 'powershell'`)
+
+### Requirement: Error Handling
+
+The completion command SHALL provide clear error messages for common failure scenarios.
+
+#### Scenario: Unsupported shell
+
+- **WHEN** user requests completion for unsupported shell (bash, fish, powershell, etc.)
+- **THEN** display error message: "Shell '<name>' is not supported yet. Currently supported: zsh"
+- **AND** exit with code 1
+
+#### Scenario: Permission errors during installation
+
+- **WHEN** installation fails due to file permission issues
+- **THEN** display clear error message indicating permission problem
+- **AND** suggest using appropriate permissions or alternative installation method
+- **AND** exit with code 1
+
+#### Scenario: Missing shell configuration directory
+
+- **WHEN** expected shell configuration directory doesn't exist
+- **THEN** create the directory automatically (with user notification)
+- **AND** proceed with installation
+
+#### Scenario: Shell not detected
+
+- **WHEN** `openspec completion install` cannot detect current shell or detects non-Zsh shell
+- **THEN** display error: "Could not detect Zsh. Please specify explicitly: openspec completion install zsh"
+- **AND** exit with code 1
+
+### Requirement: Output Format
+
+The completion command SHALL provide machine-parseable and human-readable output.
+
+#### Scenario: Script generation output
+
+- **WHEN** generating completion script to stdout
+- **THEN** output only the completion script content (no extra messages)
+- **AND** allow redirection to files: `openspec completion zsh > /path/to/_openspec`
+
+#### Scenario: Installation success output
+
+- **WHEN** installation completes successfully
+- **THEN** display formatted success message with:
+  - Checkmark indicator
+  - Installation location
+  - Next steps (shell reload instructions)
+- **AND** use colors when terminal supports it (unless `--no-color` is set)
+
+#### Scenario: Verbose installation output
+
+- **WHEN** user provides `--verbose` flag during installation
+- **THEN** display detailed steps:
+  - Shell detection result
+  - Target file paths
+  - Configuration modifications
+  - File creation confirmations
+
+### Requirement: Testing Support
+
+The completion implementation SHALL be testable with unit and integration tests.
+
+#### Scenario: Mock shell environment
+
+- **WHEN** writing tests for shell detection
+- **THEN** allow overriding `$SHELL` environment variable
+- **AND** use dependency injection for file system operations
+
+#### Scenario: Generator output verification
+
+- **WHEN** testing completion generators
+- **THEN** verify generated scripts contain expected patterns
+- **AND** test that command registry is properly consumed
+- **AND** ensure dynamic completion placeholders are present
+
+#### Scenario: Installation simulation
+
+- **WHEN** testing installation logic
+- **THEN** use temporary test directories instead of actual home directories
+- **AND** verify file creation without modifying real shell configurations
+- **AND** test path resolution logic independently
+
+## Not in Scope
+
+The following shells are **architecturally documented but not implemented** in this proposal. They will be added in future proposals:
+
+- **Bash completion** - Will use bash-completion framework with `_init_completion`, `compgen`, and `COMPREPLY`
+- **Fish completion** - Will use Fish's declarative `complete -c` syntax
+- **PowerShell completion** - Will use `Register-ArgumentCompleter` with completion result objects
+
+The plugin-based architecture (CompletionGenerator interface, command registry, dynamic providers) is designed to make adding these shells straightforward in follow-up changes.
+
+## Why
+
+Shell completions are essential for professional CLI tools and significantly improve developer experience by reducing friction, errors, and cognitive load during daily workflows.