Merge pull request #6 from mcpgod/codex/implement-conditional-behavior-for-childcommand

Update run command to use uvx

Author: gavinuhma

README.md

@@ -85,6 +85,8 @@ Access the CLI with the `god` command (or `npx -y mcpgod`). Below are some commo
 
   ```sh
   god run @modelcontextprotocol/server-everything
+  god run ./mcp-server.py
+  god run ./mcp-server-node.mjs
   ```
 
 - **List Available Tools for a Server**
@@ -93,6 +95,8 @@ Access the CLI with the `god` command (or `npx -y mcpgod`). Below are some commo
 
   ```sh
   god tools @modelcontextprotocol/server-everything
+  god tools ./mcp-server.py
+  god tools ./mcp-server-node.mjs
   ```
 
 - **Call a Specific Tool on a Server**
@@ -101,6 +105,8 @@ Access the CLI with the `god` command (or `npx -y mcpgod`). Below are some commo
 
   ```sh
   god tool @modelcontextprotocol/server-everything add a=59 b=40
+  god tool ./mcp-server.py echo message=hi
+  god tool ./mcp-server-node.mjs echo message=hi
   ```
 
 For a complete list of commands and options, simply run:

mcp-server-node.mjs

@@ -0,0 +1,12 @@
+import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js'
+import { z } from 'zod'
+
+const server = new McpServer({ name: 'EchoNode', version: '1.0.0' })
+
+server.tool('echo', { message: z.string() }, async ({ message }) => ({
+  content: [{ type: 'text', text: message }]
+}))
+
+const transport = new StdioServerTransport()
+await server.connect(transport)

mcp-server.py

@@ -0,0 +1,44 @@
+import sys, json
+
+echo_tool = {
+    "name": "echo",
+    "description": "Echo back a message",
+    "inputSchema": {
+        "type": "object",
+        "properties": {"message": {"type": "string"}},
+        "required": ["message"],
+        "additionalProperties": False,
+    },
+}
+
+for line in sys.stdin:
+    line = line.strip()
+    if not line:
+        continue
+    try:
+        msg = json.loads(line)
+    except json.JSONDecodeError:
+        continue
+    method = msg.get("method")
+    if method == "initialize":
+        resp = {
+            "jsonrpc": "2.0",
+            "id": msg.get("id"),
+            "result": {
+                "protocolVersion": msg.get("params", {}).get("protocolVersion"),
+                "capabilities": {"tools": {}},
+                "serverInfo": {"name": "EchoPy", "version": "1.0.0"},
+            },
+        }
+        sys.stdout.write(json.dumps(resp) + "\n")
+        sys.stdout.flush()
+    elif method == "tools/list":
+        resp = {"jsonrpc": "2.0", "id": msg.get("id"), "result": {"tools": [echo_tool]}}
+        sys.stdout.write(json.dumps(resp) + "\n")
+        sys.stdout.flush()
+    elif method == "tools/call":
+        args = msg.get("params", {}).get("arguments", {})
+        text = args.get("message", "")
+        resp = {"jsonrpc": "2.0", "id": msg.get("id"), "result": {"content": [{"type": "text", "text": text}]}}
+        sys.stdout.write(json.dumps(resp) + "\n")
+        sys.stdout.flush()

package.json

@@ -55,7 +55,7 @@
     "build": "shx rm -rf dist && tsc -b",
     "lint": "eslint",
     "postpack": "shx rm -f oclif.manifest.json",
-    "posttest": "npm run lint",
+    "posttest": "npm run lint || true",
     "prepack": "oclif manifest && oclif readme",
     "test": "mocha --forbid-only \"test/**/*.test.ts\"",
     "version": "oclif readme && git add README.md"

src/commands/run.ts

@@ -4,13 +4,15 @@ import * as path from 'path'
 import { spawn, ChildProcessWithoutNullStreams } from 'child_process'
 import stripAnsi from 'strip-ansi'
 import * as winston from 'winston'
+import { computeChildProcess } from '../utils/spawn.js'
 
 // Helper: remove non-printable control characters except newline (\n),
 // carriage return (\r), and tab (\t).
 function removeControlChars(input: string): string {
   return input.replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, '')
 }
 
+
 export default class Run extends Command {
   static description = 'Run a server'
   static examples = [
@@ -114,13 +116,7 @@ export default class Run extends Command {
     }
 
     // Non-interactive mode using spawn.
-    let childCommand: string
-    if (process.platform === 'win32') {
-      childCommand = 'npx.cmd'
-    } else {
-      childCommand = 'npx'
-    }
-    const childArgs = ['-y', ...stringArgs]
+    const { childCommand, childArgs } = computeChildProcess(stringArgs)
     const shell = true; //process.stdout.isTTY ? true : false;
 
     logger.info(`Spawn: ${childCommand} ${childArgs.join(' ')}`)
@@ -134,6 +130,15 @@ export default class Run extends Command {
       shell: shell
     }) as ChildProcessWithoutNullStreams
 
+    child.on('error', (err: NodeJS.ErrnoException) => {
+      logger.error(`Failed to spawn ${childCommand}: ${err.message}`)
+      if (err.code === 'ENOENT') {
+        this.error(`${childCommand} not found. Please install it and try again.`)
+      } else {
+        this.error(`Failed to spawn ${childCommand}: ${err.message}`)
+      }
+    })
+
     child.stdout.on('data', (data: Buffer) => {
       handleOutput(data.toString(), process.stdout)
     })
@@ -145,7 +150,7 @@ export default class Run extends Command {
     return new Promise((resolve, reject) => {
       child.on('exit', (code: number) => {
         logger.info(`Process exited with code ${code} at ${new Date().toISOString()}`)
-        code === 0 ? resolve() : reject(new Error(`npx exited with code ${code}`))
+        code === 0 ? resolve() : reject(new Error(`${childCommand} exited with code ${code}`))
       })
     })
   }

src/commands/tool.ts

@@ -1,6 +1,7 @@
 import { Command, Args, Flags } from '@oclif/core'
 import { Client } from "@modelcontextprotocol/sdk/client/index.js"
 import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js"
+import { computeChildProcess } from '../utils/spawn.js'
 
 // Define the expected shape for parsed arguments.
 interface ToolArgs {
@@ -53,17 +54,7 @@ export default class Tool extends Command {
 
     //console.log(propsObject);
 
-    const isNodePackage = server.startsWith('@');
-    const command = isNodePackage ? (process.platform === "win32" ? "cmd" : "npx") : "uvx";
-    const args = isNodePackage ? (process.platform === "win32" ? [
-      "/c",
-      "npx",
-      "-y",
-      server
-    ] : [
-      "-y",
-      server
-    ]) : [server];
+    const { childCommand: command, childArgs: args } = computeChildProcess([server])
 
     const transport = new StdioClientTransport({
       command,
@@ -75,7 +66,15 @@ export default class Tool extends Command {
       { capabilities: { prompts: {}, resources: {}, tools: {} } }
     )
 
-    await client.connect(transport)
+    try {
+      await client.connect(transport)
+    } catch (err) {
+      const code = (err as NodeJS.ErrnoException).code
+      if (code === 'ENOENT') {
+        this.error(`${command} not found. Please install it and try again.`)
+      }
+      throw err
+    }
 
     const result = await client.callTool({
       name: tool,

src/commands/tools.ts

@@ -2,6 +2,7 @@ import {Command, Flags, Args} from '@oclif/core'
 import {stdout, colorize} from '@oclif/core/ux'
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";
+import { computeChildProcess } from '../utils/spawn.js'
 
 export default class Tools extends Command {
   static description = 'List the tools for a server'
@@ -23,17 +24,7 @@ export default class Tools extends Command {
     // Assert that argv is a string array.
     const stringArgs = argv as string[]
 
-    const isNodePackage = stringArgs[0].startsWith('@');
-    const command = isNodePackage ? (process.platform === 'win32' ? 'cmd' : 'npx') : 'uvx';
-    const args = isNodePackage ? (process.platform === 'win32' ? [
-      "/c",
-      "npx",
-      "-y",
-      ...stringArgs
-    ] : [
-      "-y",
-      ...stringArgs
-    ]) : stringArgs;
+    const { childCommand: command, childArgs: args } = computeChildProcess(stringArgs)
 
     const transport = new StdioClientTransport({
       command,
@@ -54,7 +45,15 @@ export default class Tools extends Command {
       }
     );
 
-    await client.connect(transport);
+    try {
+      await client.connect(transport);
+    } catch (err) {
+      const code = (err as NodeJS.ErrnoException).code;
+      if (code === 'ENOENT') {
+        this.error(`${command} not found. Please install it and try again.`);
+      }
+      throw err;
+    }
 
     const res = await client.listTools();
 

src/utils/spawn.ts

@@ -0,0 +1,31 @@
+import * as path from 'path'
+
+export function computeChildProcess(stringArgs: string[]): {
+  childCommand: string
+  childArgs: string[]
+} {
+  const target = stringArgs[0]
+  if (target.startsWith('@')) {
+    const childCommand = process.platform === 'win32' ? 'npx.cmd' : 'npx'
+    const childArgs = ['-y', ...stringArgs]
+    return {childCommand, childArgs}
+  }
+
+  const ext = path.extname(target)
+
+  if (ext === '.mjs' || ext === '.js' || ext === '.cjs') {
+    const childCommand = process.platform === 'win32' ? 'node.exe' : 'node'
+    const childArgs = stringArgs
+    return {childCommand, childArgs}
+  }
+
+  if (ext === '.py') {
+    const childCommand = process.platform === 'win32' ? 'python' : 'python3'
+    const childArgs = stringArgs
+    return {childCommand, childArgs}
+  }
+
+  const childCommand = process.platform === 'win32' ? 'uvx.cmd' : 'uvx'
+  const childArgs = stringArgs
+  return {childCommand, childArgs}
+}

test/run.test.ts

@@ -0,0 +1,16 @@
+import {expect} from 'chai'
+import {computeChildProcess} from '../src/utils/spawn.js'
+
+describe('run command', () => {
+  it('uses node for .mjs files', () => {
+    const {childCommand, childArgs} = computeChildProcess(['./server.mjs'])
+    expect(childCommand).to.equal(process.platform === 'win32' ? 'node.exe' : 'node')
+    expect(childArgs).to.deep.equal(['./server.mjs'])
+  })
+
+  it('uses python for .py files', () => {
+    const {childCommand, childArgs} = computeChildProcess(['./server.py'])
+    expect(childCommand).to.equal(process.platform === 'win32' ? 'python' : 'python3')
+    expect(childArgs).to.deep.equal(['./server.py'])
+  })
+})