Improvement: Classpath is Incomplete warning should give more context

Issue #193 points out that this message can be less than helpful. The wiki points out that this occurs when opening individual java files. But the cases associated with this message suggest there are various other conditions - missing .project files, misconfigured .classpath, among others. I have an environment where I open multiple project directories in a single vscode window. I don't even know which project to start looking at when this message appears.

It would be helpful if the message could display "Classpath is incomplete" in (File or directory reference)

Environment

• Operating System: OSX
• JDK version: jdk 1.8
• Visual Studio Code version: 1.35.1
• Java extension version: 0.46.0

Steps To Reproduce

1. With (say) 3 java project directories in a vscode window, delete .project in one.
2. Java: Clean the language server environment

"Classpath is Incomplete" warning is displayed

Current Result

Expected Result

Additional Informations

issue #193 から始め、Java extension にある既存の警告 "Classpath is incomplete" を追跡します。.project ファイルを削除し、language server の環境をクリーンアップした後、1 つの VS Code ウィンドウで複数の Java プロジェクトディレクトリを使って再現します。警告が該当するファイルまたはディレクトリを特定すれば完了です。