Step 90: LSP client core

PROGRESS.md

@@ -188,6 +188,9 @@ All 38 steps implemented and passing. Each step has a corresponding test (`step1
 - [x] Step 88: **IMPLEMENTED** — Drag-and-drop file/folder open via SDL_DROPFILE (2/2 tests pass)
 - [x] Step 89: **IMPLEMENTED** — File watcher polling with auto-reload for clean buffers (1/1 tests pass)
 
+### Phase 4c: LSP Client & Diagnostics (Steps 90–96) — In Progress
+- [x] Step 90: **IMPLEMENTED** — LSPClient core with JSON-RPC initialize/shutdown, injectable transport (2/2 tests pass)
+
 ---
 
 ## Build Infrastructure
@@ -255,6 +258,7 @@ vcpkg's imgui 1.91.9 removed the `sdl2-binding` feature (only `sdl3-binding` exi
 **Step 87:** Compile and pass (2/2)
 **Step 88:** Compile and pass (2/2)
 **Step 89:** Compile and pass (1/1)
+**Step 90:** Compile and pass (2/2)
 
 ---
 
@@ -352,3 +356,4 @@ Sprint 4 in progress. Step 76 (LayoutManager) done. Next: Step 77 (custom code e
 | 2026-02-09 | Codex | Step 87: Welcome screen wired with recent files persistence and quick actions. 2/2 tests pass. |
 | 2026-02-09 | Codex | Step 88: Drag-and-drop open for files and folders. 2/2 tests pass. |
 | 2026-02-09 | Codex | Step 89: File watcher polling with auto-reload for clean buffers. 1/1 tests pass. |
+| 2026-02-09 | Codex | Step 90: LSPClient core with JSON-RPC initialize/shutdown and injectable transport. 2/2 tests pass. |

editor/CMakeLists.txt

@@ -502,6 +502,10 @@ target_include_directories(step88_test PRIVATE src)
 add_executable(step89_test tests/step89_test.cpp)
 target_include_directories(step89_test PRIVATE src)
 
+add_executable(step90_test tests/step90_test.cpp)
+target_include_directories(step90_test PRIVATE src)
+target_link_libraries(step90_test PRIVATE nlohmann_json::nlohmann_json)
+
 find_package(SDL2 CONFIG REQUIRED)
 find_package(OpenGL REQUIRED)
 find_package(glad CONFIG REQUIRED)

editor/src/LSPClient.h

@@ -0,0 +1,71 @@
+#pragma once
+// Step 90: LSP client core
+//
+// Minimal JSON-RPC LSP client with injectable transport.
+
+#include <string>
+#include <memory>
+#include <vector>
+#include <nlohmann/json.hpp>
+
+class LSPTransport {
+public:
+    virtual ~LSPTransport() = default;
+    virtual void send(const std::string& msg) = 0;
+    virtual bool receive(std::string& out) = 0;
+    virtual bool isOpen() const = 0;
+    virtual void close() = 0;
+};
+
+class LSPClient {
+public:
+    explicit LSPClient(std::shared_ptr<LSPTransport> transport)
+        : transport_(std::move(transport)) {}
+
+    void initialize(const std::string& rootUri,
+                    const std::string& clientName,
+                    int processId) {
+        nlohmann::json params;
+        params["processId"] = processId;
+        params["rootUri"] = rootUri;
+        params["clientInfo"] = { {"name", clientName}, {"version", "0.1"} };
+        params["capabilities"] = nlohmann::json::object();
+        sendRequest("initialize", params);
+        sendNotification("initialized", nlohmann::json::object());
+    }
+
+    void shutdown() {
+        sendRequest("shutdown", nlohmann::json::object());
+        sendNotification("exit", nlohmann::json::object());
+        if (transport_) transport_->close();
+    }
+
+    void sendNotification(const std::string& method, const nlohmann::json& params) {
+        nlohmann::json msg;
+        msg["jsonrpc"] = "2.0";
+        msg["method"] = method;
+        msg["params"] = params;
+        sendMessage(msg);
+    }
+
+    int sendRequest(const std::string& method, const nlohmann::json& params) {
+        nlohmann::json msg;
+        msg["jsonrpc"] = "2.0";
+        msg["id"] = nextId_++;
+        msg["method"] = method;
+        msg["params"] = params;
+        sendMessage(msg);
+        return msg["id"].get<int>();
+    }
+
+private:
+    void sendMessage(const nlohmann::json& msg) {
+        if (!transport_) return;
+        std::string body = msg.dump();
+        std::string header = "Content-Length: " + std::to_string(body.size()) + "\r\n\r\n";
+        transport_->send(header + body);
+    }
+
+    std::shared_ptr<LSPTransport> transport_;
+    int nextId_ = 1;
+};

editor/tests/step90_test.cpp

@@ -0,0 +1,50 @@
+// Step 90 TDD Test: LSP client core
+//
+// Tests:
+// 1. Initialize sends JSON-RPC initialize request
+// 2. Shutdown sends shutdown request and exit notification
+
+#include <cassert>
+#include <iostream>
+#include <string>
+#include "LSPClient.h"
+
+struct MockTransport : public LSPTransport {
+    std::vector<std::string> sent;
+    void send(const std::string& msg) override { sent.push_back(msg); }
+    bool receive(std::string& out) override { (void)out; return false; }
+    bool isOpen() const override { return true; }
+    void close() override {}
+};
+
+int main() {
+    int passed = 0;
+    int failed = 0;
+
+    // --- Test 1: initialize ---
+    {
+        auto transport = std::make_shared<MockTransport>();
+        LSPClient client(transport);
+        client.initialize("file:///tmp", "test-client", 1);
+        assert(!transport->sent.empty());
+        auto msg = transport->sent.back();
+        assert(msg.find("\"method\":\"initialize\"") != std::string::npos);
+        std::cout << "Test 1 PASS: initialize sends request" << std::endl;
+        ++passed;
+    }
+
+    // --- Test 2: shutdown + exit ---
+    {
+        auto transport = std::make_shared<MockTransport>();
+        LSPClient client(transport);
+        client.shutdown();
+        assert(transport->sent.size() >= 2);
+        assert(transport->sent[transport->sent.size()-2].find("\"method\":\"shutdown\"") != std::string::npos);
+        assert(transport->sent.back().find("\"method\":\"exit\"") != std::string::npos);
+        std::cout << "Test 2 PASS: shutdown sends shutdown+exit" << std::endl;
+        ++passed;
+    }
+
+    std::cout << "\n=== Step 90 Results: " << passed << " passed, " << failed << " failed ===" << std::endl;
+    return failed > 0 ? 1 : 0;
+}