Implement Morphir Extension System with Extism + JSON-RPC

[DamianReeves]

Summary

• Replace wasmtime-based morphir-wit-extension with new Extism-based extension system
• Add morphir-extension-sdk crate with SDK for building WASM plugin extensions
• Add morphir-gleam-binding crate with Gleam language frontend/backend extension
• Add morphir-wasm-binding crate with WASM/WAT backend extension
• Add extensions module to morphir-daemon with Extism plugin runtime

Architecture

┌──────────────────────────────────────────────────────────────────┐
│                      morphir-daemon (Hub)                         │
│  - Extism host runtime (loads/executes WASM plugins)             │
│  - JSON-RPC 2.0 server for CLI/IDE integration                   │
│  - Workspace management and project discovery                    │
│  - Extension registry and lifecycle management                   │
└──────────────────────┬───────────────────────────────────────────┘
                       │ Extism Plugin Protocol
                       │ (bytes-in → bytes-out via JSON-RPC payloads)
         ┌─────────────┼─────────────────────┐
         ▼             ▼                     ▼
┌───────────────┐ ┌───────────────┐   ┌───────────────┐
│ morphir-gleam │ │ morphir-wasm  │   │    Custom     │
│   -binding    │ │   -binding    │   │   Extension   │
│   (.wasm)     │ │   (.wasm)     │   │   (.wasm)     │
└───────────────┘ └───────────────┘   └───────────────┘
         │             │                     │
         └─────────────┴─────────────────────┘
                       │
             Built using morphir-extension-sdk

New Crates

Crate	Purpose
morphir-extension-sdk	SDK for building Morphir extensions as WASM plugins
morphir-gleam-binding	Gleam frontend + backend extension
morphir-wasm-binding	WASM/WAT backend extension

Key Dependencies Added

• extism (1.7) - WASM plugin runtime
• extism-pdk (1.2) - Plugin development kit
• reqwest (0.12 with rustls) - HTTP client for downloading extensions
• wasm-encoder (0.220) - WASM binary generation

Test plan

• cargo check passes for all crates
• CI checks pass

🤖 Generated with Claude Code

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Invoke Backend trait instead of hardcoded error result

The JSON-RPC dispatch path for generate always constructs a GenerateResult with success: false and the message “Backend not implemented” without ever calling Backend::generate on the extension type. Because __dispatch_request routes all generate calls here, any extension that implements Backend will still always return an error, so backend extensions can never run. This needs to call the trait implementation (or otherwise detect/support implemented traits) rather than returning a fixed error payload.

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[chatgpt-codex-connector]

Return workspace info via Extism memory, not 0

The host-side morphir_get_workspace_info implementation serializes WorkspaceInfo but discards the JSON and always returns Val::I64(0). In the SDK, this host function is imported as returning Json<WorkspaceInfo>, which expects a pointer to valid serialized data; returning 0 means the JSON cannot be read and get_workspace_info() will always fail. This breaks host/extension communication for workspace metadata unless you allocate/write the JSON into plugin memory and return the proper pointer (or use Extism’s helper APIs).

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