Test: MCP server extension API

[connor4312]

Ref: #243522

• anyOS @lszomoru
• anyOS @karthiknadig

Complexity: 5

Authors: @jrieken @connor4312

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This iteration we've added support for Model Context Protocol (MCP) servers that provide additional tools the LM can use in Agent mode. You can refer to #244525 for general setup/mechanics.

In addition to user-configured MCP servers, there are also extension-configured MCP servers, and we have a sample of one: https://github.com/microsoft/vscode-extension-samples/tree/main/mcp-extension-sample. There are some lifecycle complexities here that aren't present for normal config servers, and please test them:

• When an extension is installed that declares an MCP collection in its package.json contribution, you should see the 🔁 icon in chat. Clicking it should activate the extension and the servers the provider initially publishes.
• If the extension fires McpConfigurationProvider.onDidChange, you should also get a refresh button if there are any new servers that were published. Any old servers that no longer exist should be removed.
• On reload, the extension should not be activated until any of its servers are needed (they're cached). If, once the extension is activated and there are servers that no longer exist, they should be removed from the UI.
• Uninstalling an extension that provides MCP servers should also remove any cached servers from the UI.

[karthiknadig]

@connor4312 Blocked on this error:

[connor4312]

@karthiknadig where is that coming from? The sample refers to mcpConfigurationProvider https://github.com/microsoft/vscode-extension-samples/blob/main/mcp-extension-sample/package.json#L3

[karthiknadig]

Copilot got it wrong, and I did not realize.

[lszomoru]

@connor4312 , I am really struggling with this one. I am using the following minimal sample code:

	context.subscriptions.push(vscode.lm.registerMcpConfigurationProvider('exampleGist', {
		onDidChange: didChangeEmitter.event,
		provideMcpServerDefinitions: async () => {
			return [
				{
					label: 'file_system',
					command: "npx",
					args: [
						"-y",
						"@modelcontextprotocol/server-filesystem",
						"Users/lszomoru/Source/lszomoru"
					],
					env: {}
				}
			];
		}
	}));

When I run the code, I see that the Chat Panel knows about the new server, lists the number of new tools, but pressing "Refresh" hangs. Clicking on the server buttons opens a channel that has 'undefined` as the name:

In the debug console I see the following exception:

stack trace: TypeError: Cannot convert undefined or null to object
    at Function.entries (<anonymous>)
    at Ky.n (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:195:318)
    at Ky.g (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:194:849)
    at Ky.$startMcp (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:120:5916)
    at r4.S (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:115966)
    at r4.Q (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:115746)
    at r4.M (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:114835)
    at r4.L (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:113940)
    at Th.value (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:112737)
    at D.B (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:27:2375)
    at D.fire (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:27:2593)
    at Jn.fire (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:9459)
    at Th.value (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:197:3909)
    at D.B (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:27:2375)
    at D.fire (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:27:2593)
    at Jn.fire (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:29:9459)
    at MessagePortMain.<anonymous> (file:///Applications/Visual%20Studio%20Code%20-%20Insiders.app/Contents/Resources/app/out/vs/workbench/api/node/extensionHostProcess.js:197:2201)
    at MessagePortMain.emit (node:events:518:28)
    at Object.MessagePortMain._internalPort.emit (node:electron/js2c/utility_init:2:2949)
    at Object.callbackTrampoline (node:internal/async_hooks:130:17)