refactor: reuse shared JSON object guard

packages/agentctx/src/mcp/server.ts

@@ -13,6 +13,7 @@
  * nothing throws raw into the channel.
  */
 import { createInterface } from "node:readline";
+import { isJsonObject } from "../claude/json-file.js";
 import { VERSION } from "../version.js";
 import { type ToolContext, type ToolDefinition, callTool } from "./tools.js";
 
@@ -82,13 +83,13 @@ export function serveMcp(options: McpServerOptions): Promise<void> {
 
 /** Returns the response to write, or null for notifications. */
 function handleMessage(message: unknown, options: McpServerOptions): JsonRpcResponse | null {
-  if (!isObject(message) || message.jsonrpc !== "2.0" || typeof message.method !== "string") {
+  if (!isJsonObject(message) || message.jsonrpc !== "2.0" || typeof message.method !== "string") {
     return error(idOf(message), INVALID_REQUEST, "expected a JSON-RPC 2.0 request");
   }
 
   const id = idOf(message);
   const isNotification = !("id" in message);
-  const params = isObject(message.params) ? message.params : {};
+  const params = isJsonObject(message.params) ? message.params : {};
 
   switch (message.method) {
     case "initialize":
@@ -111,7 +112,7 @@ function handleMessage(message: unknown, options: McpServerOptions): JsonRpcResp
       if (typeof params.name !== "string") {
         return error(id, INVALID_PARAMS, "tools/call requires a string 'name'");
       }
-      const args = isObject(params.arguments) ? params.arguments : {};
+      const args = isJsonObject(params.arguments) ? params.arguments : {};
       const { payload, isError } = callTool(options.tools, options.context, params.name, args);
       return result(id, {
         content: [{ type: "text", text: JSON.stringify(payload) }],
@@ -143,12 +144,8 @@ function error(id: JsonRpcId, code: number, message: string): JsonRpcResponse {
 }
 
 function idOf(message: unknown): JsonRpcId {
-  if (isObject(message) && (typeof message.id === "string" || typeof message.id === "number")) {
+  if (isJsonObject(message) && (typeof message.id === "string" || typeof message.id === "number")) {
     return message.id;
   }
   return null;
 }
-
-function isObject(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value);
-}

packages/agentctx/src/profile/detect.ts

@@ -10,6 +10,7 @@
 import { existsSync, readFileSync } from "node:fs";
 import { join } from "node:path";
 import type { Database } from "better-sqlite3";
+import { isJsonObject } from "../claude/json-file.js";
 import { insertRecord, listRecords } from "../storage/records.js";
 import { BODY_MAX_CHARS } from "../storage/types.js";
 
@@ -152,7 +153,7 @@ function detectStack(dir: string, pkg: PackageJson | null): string[] {
   const lines: string[] = [];
 
   if (pkg !== null) {
-    const engines = isObject(pkg.engines) ? pkg.engines : {};
+    const engines = isJsonObject(pkg.engines) ? pkg.engines : {};
     const nodeRange = typeof engines.node === "string" ? ` (node ${engines.node})` : "";
     lines.push(`Runtime: Node.js${nodeRange}`);
 
@@ -192,7 +193,7 @@ function detectStack(dir: string, pkg: PackageJson | null): string[] {
 }
 
 function detectCommands(dir: string, pkg: PackageJson): string[] {
-  const scripts = isObject(pkg.scripts) ? pkg.scripts : {};
+  const scripts = isJsonObject(pkg.scripts) ? pkg.scripts : {};
   const names = Object.keys(scripts).filter((name) => typeof scripts[name] === "string");
   if (names.length === 0) {
     return [];
@@ -212,7 +213,7 @@ function detectEntryPoints(pkg: PackageJson): string[] {
 
   if (typeof pkg.bin === "string") {
     lines.push(`bin: ${pkg.bin}`);
-  } else if (isObject(pkg.bin)) {
+  } else if (isJsonObject(pkg.bin)) {
     for (const [name, target] of Object.entries(pkg.bin)) {
       lines.push(`bin ${name}: ${String(target)}`);
     }
@@ -224,7 +225,9 @@ function detectEntryPoints(pkg: PackageJson): string[] {
     lines.push(`module: ${pkg.module}`);
   }
   if (pkg.exports !== undefined) {
-    const keys = isObject(pkg.exports) ? Object.keys(pkg.exports).join(", ") : String(pkg.exports);
+    const keys = isJsonObject(pkg.exports)
+      ? Object.keys(pkg.exports).join(", ")
+      : String(pkg.exports);
     lines.push(`exports: ${keys}`);
   }
 
@@ -262,7 +265,7 @@ function scriptRunner(packageManager: string | null): string {
 function collectDependencies(pkg: PackageJson): Set<string> {
   const deps = new Set<string>();
   for (const group of [pkg.dependencies, pkg.devDependencies]) {
-    if (isObject(group)) {
+    if (isJsonObject(group)) {
       for (const name of Object.keys(group)) {
         deps.add(name);
       }
@@ -275,7 +278,7 @@ function workspacePackages(workspaces: unknown): string[] {
   if (Array.isArray(workspaces)) {
     return workspaces.filter((workspace): workspace is string => typeof workspace === "string");
   }
-  if (isObject(workspaces) && Array.isArray(workspaces.packages)) {
+  if (isJsonObject(workspaces) && Array.isArray(workspaces.packages)) {
     return workspaces.packages.filter(
       (workspace): workspace is string => typeof workspace === "string",
     );
@@ -286,16 +289,12 @@ function workspacePackages(workspaces: unknown): string[] {
 function readPackageJson(dir: string): PackageJson | null {
   try {
     const parsed: unknown = JSON.parse(readFileSync(join(dir, "package.json"), "utf8"));
-    return isObject(parsed) ? (parsed as PackageJson) : null;
+    return isJsonObject(parsed) ? (parsed as PackageJson) : null;
   } catch {
     return null;
   }
 }
 
-function isObject(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value);
-}
-
 function clip(body: string): string {
   return body.length <= BODY_MAX_CHARS ? body : `${body.slice(0, BODY_MAX_CHARS - 1)}…`;
 }