chore: add more information when there is a failure connecting MCP-92

src/common/connectionManager.ts

@@ -109,6 +109,7 @@ export class ConnectionManager extends EventEmitter<ConnectionManagerEvents> {
 
         let serviceProvider: NodeDriverServiceProvider;
         let connectionInfo: ConnectionInfo;
+        let connectionStringAuthType: ConnectionStringAuthType = "scram";
 
         try {
             settings = { ...settings };
@@ -137,6 +138,11 @@ export class ConnectionManager extends EventEmitter<ConnectionManagerEvents> {
             connectionInfo.driverOptions.proxy ??= { useEnvironmentVariableProxies: true };
             connectionInfo.driverOptions.applyProxyToOIDC ??= true;
 
+            connectionStringAuthType = ConnectionManager.inferConnectionTypeFromSettings(
+                this.userConfig,
+                connectionInfo
+            );
+
             serviceProvider = await NodeDriverServiceProvider.connect(
                 connectionInfo.connectionString,
                 {
@@ -152,6 +158,7 @@ export class ConnectionManager extends EventEmitter<ConnectionManagerEvents> {
             this.changeState("connection-errored", {
                 tag: "errored",
                 errorReason,
+                connectionStringAuthType,
                 connectedAtlasCluster: settings.atlas,
             });
             throw new MongoDBError(ErrorCodes.MisconfiguredConnectionString, errorReason);
@@ -184,6 +191,7 @@ export class ConnectionManager extends EventEmitter<ConnectionManagerEvents> {
             this.changeState("connection-errored", {
                 tag: "errored",
                 errorReason,
+                connectionStringAuthType,
                 connectedAtlasCluster: settings.atlas,
             });
             throw new MongoDBError(ErrorCodes.NotConnectedToMongoDB, errorReason);

src/common/session.ts

@@ -10,6 +10,7 @@ import type {
     ConnectionManager,
     ConnectionSettings,
     ConnectionStateConnected,
+    ConnectionStateErrored,
 } from "./connectionManager.js";
 import type { NodeDriverServiceProvider } from "@mongosh/service-provider-node-driver";
 import { ErrorCodes, MongoDBError } from "./errors.js";
@@ -28,7 +29,7 @@ export type SessionEvents = {
     connect: [];
     close: [];
     disconnect: [];
-    "connection-error": [string];
+    "connection-error": [ConnectionStateErrored];
 };
 
 export class Session extends EventEmitter<SessionEvents> {
@@ -67,9 +68,9 @@ export class Session extends EventEmitter<SessionEvents> {
         this.exportsManager = exportsManager;
         this.connectionManager = connectionManager;
         this.connectionManager.on("connection-succeeded", () => this.emit("connect"));
-        this.connectionManager.on("connection-timed-out", (error) => this.emit("connection-error", error.errorReason));
+        this.connectionManager.on("connection-timed-out", (error) => this.emit("connection-error", error));
         this.connectionManager.on("connection-closed", () => this.emit("disconnect"));
-        this.connectionManager.on("connection-errored", (error) => this.emit("connection-error", error.errorReason));
+        this.connectionManager.on("connection-errored", (error) => this.emit("connection-error", error));
     }
 
     setMcpClient(mcpClient: Implementation | undefined): void {
@@ -136,13 +137,7 @@ export class Session extends EventEmitter<SessionEvents> {
     }
 
     async connectToMongoDB(settings: ConnectionSettings): Promise<void> {
-        try {
-            await this.connectionManager.connect({ ...settings });
-        } catch (error: unknown) {
-            const message = error instanceof Error ? error.message : (error as string);
-            this.emit("connection-error", message);
-            throw error;
-        }
+        await this.connectionManager.connect({ ...settings });
     }
 
     get isConnectedToMongoDB(): boolean {

src/resources/common/debug.ts

@@ -1,13 +1,13 @@
 import { ReactiveResource } from "../resource.js";
 import type { Telemetry } from "../../telemetry/telemetry.js";
 import type { Session, UserConfig } from "../../lib.js";
+import type { AtlasClusterConnectionInfo, ConnectionStateErrored } from "../../common/connectionManager.js";
 
 type ConnectionStateDebuggingInformation = {
     readonly tag: "connected" | "connecting" | "disconnected" | "errored";
     readonly connectionStringAuthType?: "scram" | "ldap" | "kerberos" | "oidc-auth-flow" | "oidc-device-flow" | "x.509";
-    readonly oidcLoginUrl?: string;
-    readonly oidcUserCode?: string;
     readonly errorReason?: string;
+    readonly connectedAtlasCluster?: AtlasClusterConnectionInfo;
 };
 
 export class DebugResource extends ReactiveResource<
@@ -35,15 +35,21 @@ export class DebugResource extends ReactiveResource<
     }
     reduce(
         eventName: "connect" | "disconnect" | "close" | "connection-error",
-        event: string | undefined
+        event: ConnectionStateErrored | undefined
     ): ConnectionStateDebuggingInformation {
-        void event;
-
         switch (eventName) {
             case "connect":
                 return { tag: "connected" };
-            case "connection-error":
-                return { tag: "errored", errorReason: event };
+            case "connection-error": {
+                return {
+                    tag: "errored",
+                    connectionStringAuthType: event?.connectionStringAuthType,
+                    connectedAtlasCluster: event?.connectedAtlasCluster,
+                    errorReason:
+                        event?.errorReason ??
+                        "Could not find a reason. This might be a bug in the MCP Server. Please open an issue in https://github.com/mongodb-js/mongodb-mcp-server.",
+                };
+            }
             case "disconnect":
             case "close":
                 return { tag: "disconnected" };
@@ -59,6 +65,11 @@ export class DebugResource extends ReactiveResource<
                 break;
             case "errored":
                 result += `The user is not connected to a MongoDB cluster because of an error.\n`;
+                if (this.current.connectedAtlasCluster) {
+                    result += `Attempted connecting to Atlas Cluster "${this.current.connectedAtlasCluster.clusterName}" in project with id "${this.current.connectedAtlasCluster.projectId}".\n`;
+                }
+
+                result += `The inferred authentication mechanism is "${this.current.connectionStringAuthType ?? "could-not-infer"}".\n`;
                 result += `<error>${this.current.errorReason}</error>`;
                 break;
             case "connecting":

tests/integration/common/connectionManager.test.ts

@@ -119,7 +119,49 @@ describeWithMongoDB("Connection Manager", (integration) => {
             });
 
             it("should notify that it failed connecting", () => {
-                expect(connectionManagerSpies["connection-errored"]).toHaveBeenCalled();
+                expect(connectionManagerSpies["connection-errored"]).toHaveBeenCalledWith({
+                    tag: "errored",
+                    connectedAtlasCluster: undefined,
+                    connectionStringAuthType: "scram",
+                    errorReason: "Unable to parse localhost:xxxxx with URL",
+                });
+            });
+
+            it("should be marked explicitly as connected", () => {
+                expect(connectionManager().currentConnectionState.tag).toEqual("errored");
+            });
+        });
+
+        describe("when fails to connect to a new atlas cluster", () => {
+            const atlas = {
+                username: "",
+                projectId: "",
+                clusterName: "My Atlas Cluster",
+                expiryDate: new Date(),
+            };
+
+            beforeEach(async () => {
+                try {
+                    await connectionManager().connect({
+                        connectionString: "mongodb://localhost:xxxxx",
+                        atlas,
+                    });
+                } catch (_error: unknown) {
+                    void _error;
+                }
+            });
+
+            it("should notify that it was disconnected before connecting", () => {
+                expect(connectionManagerSpies["connection-closed"]).toHaveBeenCalled();
+            });
+
+            it("should notify that it failed connecting", () => {
+                expect(connectionManagerSpies["connection-errored"]).toHaveBeenCalledWith({
+                    tag: "errored",
+                    connectedAtlasCluster: atlas,
+                    connectionStringAuthType: "scram",
+                    errorReason: "Unable to parse localhost:xxxxx with URL",
+                });
             });
 
             it("should be marked explicitly as connected", () => {

tests/unit/resources/common/debug.test.ts

@@ -47,10 +47,51 @@ describe("debug resource", () => {
     });
 
     it("should be disconnected and contain an error when an error event occurred", () => {
-        debugResource.reduceApply("connection-error", "Error message from the server");
+        debugResource.reduceApply("connection-error", {
+            tag: "errored",
+            errorReason: "Error message from the server",
+        });
+
+        const output = debugResource.toOutput();
+
+        expect(output).toContain(`The user is not connected to a MongoDB cluster because of an error.`);
+        expect(output).toContain(`<error>Error message from the server</error>`);
+    });
+
+    it("should show the inferred authentication type", () => {
+        debugResource.reduceApply("connection-error", {
+            tag: "errored",
+            connectionStringAuthType: "scram",
+            errorReason: "Error message from the server",
+        });
+
+        const output = debugResource.toOutput();
+
+        expect(output).toContain(`The user is not connected to a MongoDB cluster because of an error.`);
+        expect(output).toContain(`The inferred authentication mechanism is "scram".`);
+        expect(output).toContain(`<error>Error message from the server</error>`);
+    });
+
+    it("should show the atlas cluster information when provided", () => {
+        debugResource.reduceApply("connection-error", {
+            tag: "errored",
+            connectionStringAuthType: "scram",
+            errorReason: "Error message from the server",
+            connectedAtlasCluster: {
+                clusterName: "My Test Cluster",
+                projectId: "COFFEEFABADA",
+                username: "",
+                expiryDate: new Date(),
+            },
+        });
+
         const output = debugResource.toOutput();
 
         expect(output).toContain(`The user is not connected to a MongoDB cluster because of an error.`);
+        expect(output).toContain(
+            `Attempted connecting to Atlas Cluster "My Test Cluster" in project with id "COFFEEFABADA".`
+        );
+        expect(output).toContain(`The inferred authentication mechanism is "scram".`);
         expect(output).toContain(`<error>Error message from the server</error>`);
     });
 });