refactor(shim): implement lite ShimProvider interface (#75)

Author: CalvinAllen

CONTRIBUTING.md

@@ -205,28 +205,46 @@ For detailed guidelines and examples, see [Commit Convention Guide](docs/COMMIT_
 To add support for a new runtime (e.g., Ruby):
 
 1. Create `src/runtimes/ruby/provider.go`
-2. Implement the `runtime.Provider` interface:
+2. Implement the `runtime.Provider` interface (which embeds `runtime.ShimProvider`):
    ```go
    type Provider struct {}
 
+   // ShimProvider methods (used by the shim binary)
    func (p *Provider) Name() string { return "ruby" }
    func (p *Provider) DisplayName() string { return "Ruby" }
-   // ... implement all other methods
+   func (p *Provider) Shims() []string { return []string{"ruby", "gem", "bundle"} }
+   func (p *Provider) ExecutablePath(version string) (string, error) { ... }
+   func (p *Provider) IsInstalled(version string) (bool, error) { ... }
+   func (p *Provider) ShouldReshimAfter(shimName string, args []string) bool { ... }
+
+   // Provider-only methods (used by CLI, can include net/http)
+   func (p *Provider) Install(version string) error { ... }
+   func (p *Provider) ListAvailable() ([]runtime.AvailableVersion, error) { ... }
+   // ... implement remaining methods
    ```
 3. Register the provider in the `init()` function:
    ```go
    func init() {
        runtime.Register(NewProvider())
    }
    ```
-4. Import the provider in `src/main.go`:
+4. Import the provider in **both** files:
+   - `src/main.go` (for the CLI)
+   - `src/cmd/shim/main.go` (for the shim)
    ```go
    _ "github.com/dtvem/dtvem/src/runtimes/ruby"
    ```
-5. Implement the `Shims()` method to define which executables this runtime provides
-6. Implement the `ShouldReshimAfter()` method for automatic reshim detection
-7. Add tests using the provider contract harness
-8. Update README.md to reflect the new runtime support
+5. Add tests using the provider contract harness
+6. Update README.md to reflect the new runtime support
+
+### ShimProvider vs Provider
+
+The `Provider` interface embeds `ShimProvider`. This separation exists for performance:
+
+- **ShimProvider**: Minimal interface used by the shim binary. Methods here should NOT import `net/http` or other heavy dependencies.
+- **Provider**: Full interface for CLI operations. Can use any dependencies.
+
+Go's linker eliminates unused code, so keeping `ShimProvider` methods dependency-free results in a smaller, faster shim binary (~4.5MB vs ~10MB).
 
 ## Testing Guidelines
 

README.md

@@ -208,25 +208,23 @@ Reads .dtvem/runtimes.json → {"python": "3.11.0"}
 Executes: ~/.dtvem/versions/python/3.11.0/bin/python --version
 ```
 
-### Auto-Install Missing Versions
+### Missing Version Handling
 
-When you run a command that requires a version that isn't installed yet, dtvem will offer to install it automatically:
+When you run a command that requires a version that isn't installed yet, dtvem will tell you how to install it:
 
 ```bash
 $ python --version
-⚠ Python 3.11.0 is not installed
-→ Install it now? [Y/n]: y
-→ Installing Python 3.11.0...
-✓ Successfully installed Python 3.11.0
-Python 3.11.0
+✗ Python 3.11.0 is configured but not installed
+→ To install, run: dtvem install python 3.11.0
 ```
 
-This works seamlessly with bulk install - just clone a repo with a `.dtvem/runtimes.json` file and start using it. The first time you run a command, dtvem will offer to install the required version.
-
-**Environment Variable Control:**
-- `DTVEM_AUTO_INSTALL=false` - Disable auto-install in CI/automation
-- `DTVEM_AUTO_INSTALL=true` - Auto-install without prompting
-- Default - Interactive prompt
+**Bulk Install from Config:**
+Clone a repo with a `.dtvem/runtimes.json` file and run:
+```bash
+dtvem install          # Prompts for confirmation
+dtvem install --yes    # Skip confirmation
+```
+This installs all configured versions at once.
 
 ### System PATH Fallback
 
@@ -369,10 +367,6 @@ System-wide default versions (JSON format):
 ### Environment Variables
 
 - `DTVEM_ROOT`: Override default dtvem directory (default: `~/.dtvem`)
-- `DTVEM_AUTO_INSTALL`: Control auto-install behavior when a configured version is missing
-  - `false` - Disable auto-install prompts (useful for CI/automation)
-  - `true` - Auto-install without prompting
-  - Not set - Interactive prompt (default)
 
 ## Supported Runtimes
 
@@ -462,31 +456,49 @@ Remove this installation? [y/N]: y
 
 ## Plugin System
 
-dtvem uses an embedded plugin system with a registry pattern. Each runtime provider owns its shim definitions (executables it provides), making the architecture fully decentralized:
+dtvem uses an embedded plugin system with a registry pattern. Each runtime provider owns its shim definitions (executables it provides), making the architecture fully decentralized.
+
+### Provider Interfaces
+
+Providers implement two interfaces - a lightweight `ShimProvider` for the shim binary, and the full `Provider` for the CLI:
 
 ```go
-// Each runtime implements the Provider interface (19 methods)
-type Provider interface {
+// ShimProvider - minimal interface used by the shim binary
+// Excludes heavy dependencies like net/http to keep shim fast and small
+type ShimProvider interface {
     Name() string                                    // e.g., "python"
     DisplayName() string                             // e.g., "Python"
     Shims() []string                                 // e.g., ["python", "python3", "pip", "pip3"]
+    ExecutablePath(version string) (string, error)
+    IsInstalled(version string) (bool, error)
     ShouldReshimAfter(shimName, args) bool           // e.g., detect "npm install -g"
+}
+
+// Provider - full interface for CLI operations (embeds ShimProvider)
+type Provider interface {
+    ShimProvider
     Install(version string) error
+    ListAvailable() ([]AvailableVersion, error)     // requires net/http
     DetectInstalled() ([]DetectedVersion, error)
-    // ... 13 more methods
+    // ... more methods
 }
+```
+
+**Why two interfaces?** The shim binary runs on every `node`, `python`, `npm` command. By using `ShimProvider`, Go's linker eliminates unused code (like `net/http`), reducing shim size from ~10MB to ~4.5MB and improving startup time.
 
+### Adding a New Runtime
+
+1. Create `src/runtimes/<name>/provider.go`
+2. Implement the `Provider` interface (which includes all `ShimProvider` methods)
+3. Import in `src/main.go` and `src/cmd/shim/main.go`
+
+```go
 // Runtimes auto-register on startup
 func init() {
     runtime.Register(NewProvider())
 }
 ```
 
-**Adding a new runtime is as simple as:**
-1. Create `src/runtimes/<name>/provider.go`
-2. Implement the `Provider` interface (including `Shims()` and `ShouldReshimAfter()`)
-3. Import in `src/main.go`
-
 **That's it!** The shim mappings are automatically registered via the `Shims()` method, and automatic reshim detection works via `ShouldReshimAfter()`. No need to modify central mapping files.
 
 ## Development

src/cmd/shim/main.go

@@ -34,8 +34,8 @@ func runShim() error {
 	// Determine which runtime this shim belongs to
 	runtimeName := mapShimToRuntime(shimName)
 
-	// Get the runtime provider
-	provider, err := runtime.Get(runtimeName)
+	// Get the runtime provider (using ShimProvider interface for minimal dependencies)
+	provider, err := runtime.GetShimProvider(runtimeName)
 	if err != nil {
 		return fmt.Errorf("runtime provider not found: %w", err)
 	}
@@ -47,35 +47,22 @@ func runShim() error {
 		return handleNoConfiguredVersion(shimName, runtimeName, provider)
 	}
 
-	// Get the path to the actual executable
-	execPath, err := provider.ExecutablePath(version)
+	// Check if the version is installed
+	installed, err := provider.IsInstalled(version)
 	if err != nil {
-		// Check if the version is not installed
-		if strings.Contains(err.Error(), "not found") {
-			// Offer to install it
-			if shouldAutoInstall(provider.DisplayName(), version) {
-				ui.Info("Installing %s %s...", provider.DisplayName(), version)
-
-				if installErr := provider.Install(version); installErr != nil {
-					ui.Error("Failed to install %s %s: %v", provider.DisplayName(), version, installErr)
-					ui.Info("Please install manually with: dtvem install %s %s", runtimeName, version)
-					return fmt.Errorf("installation failed")
-				}
+		return fmt.Errorf("could not check if %s %s is installed: %w", runtimeName, version, err)
+	}
 
-				ui.Success("Successfully installed %s %s", provider.DisplayName(), version)
+	if !installed {
+		ui.Error("%s %s is configured but not installed", provider.DisplayName(), version)
+		ui.Info("To install, run: dtvem install %s %s", runtimeName, version)
+		return fmt.Errorf("version not installed")
+	}
 
-				// Retry getting the executable path
-				execPath, err = provider.ExecutablePath(version)
-				if err != nil {
-					return fmt.Errorf("could not find %s %s after installation: %w", runtimeName, version, err)
-				}
-			} else {
-				ui.Info("To install manually, run: dtvem install %s %s", runtimeName, version)
-				return fmt.Errorf("installation declined")
-			}
-		} else {
-			return fmt.Errorf("could not find %s %s: %w", runtimeName, version, err)
-		}
+	// Get the path to the actual executable
+	execPath, err := provider.ExecutablePath(version)
+	if err != nil {
+		return fmt.Errorf("could not find %s %s executable: %w", runtimeName, version, err)
 	}
 
 	// If the shim name differs from the base runtime name,
@@ -109,7 +96,7 @@ func runShim() error {
 
 // handleNoConfiguredVersion handles the case when no dtvem version is configured
 // It attempts to fallback to system PATH or prompts for installation
-func handleNoConfiguredVersion(shimName, runtimeName string, provider runtime.Provider) error {
+func handleNoConfiguredVersion(shimName, runtimeName string, provider runtime.ShimProvider) error {
 	// Try to find the executable deeper in PATH (system installation)
 	systemPath := findInSystemPath(shimName)
 
@@ -194,12 +181,6 @@ func findInSystemPath(execName string) string {
 	return ""
 }
 
-// shouldAutoInstall prompts the user to install a missing version.
-// Delegates to ui.PromptInstall for consistent behavior across CLI and shim.
-func shouldAutoInstall(displayName, version string) bool {
-	return ui.PromptInstall(displayName, version)
-}
-
 // getShimName returns the name of this shim binary
 func getShimName() string {
 	shimPath := os.Args[0]
@@ -216,8 +197,8 @@ func getShimName() string {
 // This queries all registered providers for their shims, eliminating the need
 // for a central hardcoded mapping.
 func mapShimToRuntime(shimName string) string {
-	// Get all registered providers
-	providers := runtime.GetAll()
+	// Get all registered providers (using ShimProvider interface)
+	providers := runtime.GetAllShimProviders()
 
 	// Check each provider's shims for an exact match first
 	for _, provider := range providers {

src/internal/runtime/provider.go

@@ -1,8 +1,10 @@
 // Package runtime defines the provider interface and registry for runtime managers
 package runtime
 
-// Provider defines the interface that all runtime providers must implement
-type Provider interface {
+// ShimProvider defines the minimal interface needed by the shim executable.
+// This interface excludes heavy operations like Install() and ListAvailable()
+// that require net/http and other dependencies not needed for shim execution.
+type ShimProvider interface {
 	// Name returns the name of the runtime (e.g., "python", "node", "ruby")
 	Name() string
 
@@ -14,6 +16,25 @@ type Provider interface {
 	// Node.js returns ["node", "npm", "npx"]
 	Shims() []string
 
+	// ExecutablePath returns the path to the main executable for a given version
+	// For example, for Python 3.11.0, this might return "/path/to/python3.11"
+	ExecutablePath(version string) (string, error)
+
+	// IsInstalled checks if a specific version is installed
+	IsInstalled(version string) (bool, error)
+
+	// ShouldReshimAfter checks if the given command should trigger a reshim.
+	// Returns true if the command installs or uninstalls global packages that add/remove executables.
+	// The shimName parameter indicates which shim was invoked (e.g., "npm", "pip")
+	// The args parameter contains the command arguments (e.g., ["install", "-g", "typescript"])
+	ShouldReshimAfter(shimName string, args []string) bool
+}
+
+// Provider defines the full interface that all runtime providers must implement.
+// It embeds ShimProvider and adds operations that require heavier dependencies.
+type Provider interface {
+	ShimProvider
+
 	// Install downloads and installs a specific version of the runtime
 	Install(version string) error
 
@@ -27,13 +48,6 @@ type Provider interface {
 	// This might query online sources or use cached data
 	ListAvailable() ([]AvailableVersion, error)
 
-	// ExecutablePath returns the path to the main executable for a given version
-	// For example, for Python 3.11.0, this might return "/path/to/python3.11"
-	ExecutablePath(version string) (string, error)
-
-	// IsInstalled checks if a specific version is installed
-	IsInstalled(version string) (bool, error)
-
 	// InstallPath returns the installation directory for a given version
 	InstallPath(version string) (string, error)
 
@@ -72,10 +86,4 @@ type Provider interface {
 	// Used to provide help text to users if automatic package installation fails
 	// Returns empty string if the runtime doesn't support global packages
 	ManualPackageInstallCommand(packages []string) string
-
-	// ShouldReshimAfter checks if the given command should trigger a reshim.
-	// Returns true if the command installs or uninstalls global packages that add/remove executables.
-	// The shimName parameter indicates which shim was invoked (e.g., "npm", "pip")
-	// The args parameter contains the command arguments (e.g., ["install", "-g", "typescript"])
-	ShouldReshimAfter(shimName string, args []string) bool
 }

src/internal/runtime/registry.go

@@ -132,3 +132,20 @@ func Unregister(name string) error {
 func GetRegistry() *Registry {
 	return globalRegistry
 }
+
+// GetShimProvider retrieves a provider as ShimProvider from the global registry.
+// This returns only the minimal interface needed by the shim.
+func GetShimProvider(name string) (ShimProvider, error) {
+	return globalRegistry.Get(name)
+}
+
+// GetAllShimProviders returns all providers as ShimProviders from the global registry.
+// This returns only the minimal interface needed by the shim.
+func GetAllShimProviders() []ShimProvider {
+	providers := globalRegistry.GetAll()
+	shimProviders := make([]ShimProvider, len(providers))
+	for i, p := range providers {
+		shimProviders[i] = p
+	}
+	return shimProviders
+}