feat: add LSP support (TypeScript and Python) (#474)

Co-authored-by: letta-code <248085862+letta-code@users.noreply.github.com>
Co-authored-by: Charles Packer <cpacker@users.noreply.github.com>
Co-authored-by: Letta <noreply@letta.com>
Co-authored-by: cpacker <packercharles@gmail.com>

src/tools/impl/ReadLSP.ts

@@ -0,0 +1,100 @@
+/**
+ * LSP-enhanced Read tool - wraps the base Read tool and adds LSP diagnostics
+ * This is used when LETTA_ENABLE_LSP is set
+ */
+import { read as baseRead } from "./Read.js";
+
+// Format a single diagnostic in opencode style: "ERROR [line:col] message"
+function formatDiagnostic(diag: {
+  severity?: number;
+  range: { start: { line: number; character: number } };
+  message: string;
+}): string {
+  const severityMap: Record<number, string> = {
+    1: "ERROR",
+    2: "WARN",
+    3: "INFO",
+    4: "HINT",
+  };
+  const severity = severityMap[diag.severity || 1] || "ERROR";
+  const line = diag.range.start.line + 1; // Convert to 1-based
+  const col = diag.range.start.character + 1;
+  return `${severity} [${line}:${col}] ${diag.message}`;
+}
+
+interface ReadLSPArgs {
+  file_path: string;
+  offset?: number;
+  limit?: number;
+  include_types?: boolean;
+}
+
+interface ReadLSPResult {
+  content: string;
+}
+
+export async function read_lsp(args: ReadLSPArgs): Promise<ReadLSPResult> {
+  // First, call the base read function
+  const result = await baseRead(args);
+
+  // Skip LSP if not enabled (shouldn't happen since we only load this when enabled)
+  if (!process.env.LETTA_ENABLE_LSP) {
+    return result;
+  }
+
+  // Determine if we should include diagnostics
+  const lineCount = result.content.split("\n").length;
+  const shouldInclude =
+    args.include_types === true ||
+    (args.include_types !== false && lineCount < 500);
+
+  if (!shouldInclude) {
+    return result;
+  }
+
+  try {
+    // Import LSP manager dynamically
+    const { lspManager } = await import("../../lsp/manager.js");
+    const path = await import("node:path");
+
+    // Resolve the path
+    const userCwd = process.env.USER_CWD || process.cwd();
+    const resolvedPath = path.default.isAbsolute(args.file_path)
+      ? args.file_path
+      : path.default.resolve(userCwd, args.file_path);
+
+    // Touch the file (opens it in LSP if not already open)
+    await lspManager.touchFile(resolvedPath, false);
+
+    // Wait briefly for diagnostics (LSP servers are async)
+    await new Promise((resolve) => setTimeout(resolve, 100));
+
+    // Get diagnostics
+    const diagnostics = lspManager.getDiagnostics(resolvedPath);
+
+    if (diagnostics.length > 0) {
+      // Only show errors (severity 1) like opencode does
+      const errors = diagnostics.filter((d) => d.severity === 1);
+      if (errors.length === 0) {
+        return result;
+      }
+
+      const maxDiagnostics = 10;
+      const displayed = errors.slice(0, maxDiagnostics);
+      const suffix =
+        errors.length > maxDiagnostics
+          ? `\n... and ${errors.length - maxDiagnostics} more`
+          : "";
+
+      return {
+        content: `${result.content}\n\nThis file has errors, please fix\n<file_diagnostics>\n${displayed.map(formatDiagnostic).join("\n")}${suffix}\n</file_diagnostics>`,
+      };
+    }
+
+    // No errors - return as-is
+    return result;
+  } catch (_error) {
+    // If LSP fails, silently return the base result
+    return result;
+  }
+}