feat: support environment variables reference in mcp env config

Author: NamesMT

src/services/mcp/McpHub.ts

@@ -30,6 +30,7 @@ import {
 } from "../../shared/mcp"
 import { fileExistsAtPath } from "../../utils/fs"
 import { arePathsEqual } from "../../utils/path"
+import { injectEnv } from "../../utils/config"
 
 export type McpConnection = {
 	server: McpServer
@@ -452,7 +453,7 @@ export class McpHub {
 					args: config.args,
 					cwd: config.cwd,
 					env: {
-						...config.env,
+						...(config.env ? await injectEnv(config.env) : {}),
 						...(process.env.PATH ? { PATH: process.env.PATH } : {}),
 					},
 					stderr: "pipe",

src/utils/config.ts

@@ -0,0 +1,21 @@
+/**
+ * Deeply injects environment variables into a configuration object/string/json
+ *
+ * Uses VSCode env:name pattern: https://code.visualstudio.com/docs/reference/variables-reference#_environment-variables
+ *
+ * Does not mutate original object
+ */
+export async function injectEnv(config: string | Record<PropertyKey, any>, notFoundValue: any = "") {
+	// Use simple regex replace for now, will see if object traversal and recursion is needed here (e.g: for non-serializable objects)
+
+	const isObject = typeof config === "object"
+	let _config: string = isObject ? JSON.stringify(config) : config
+
+	_config = _config.replace(/\$\{env:([\w\.]+)\}/g, (_, name) => {
+		if (!process.env[name]) console.warn(`[injectEnv] env variable ${name} referenced but not found in process.env`)
+
+		return process.env[name] || notFoundValue
+	})
+
+	return isObject ? JSON.parse(_config) : _config
+}