Diagnostics do not work on symlinked files

[mjuraj]

Syntax highlighting does not work on symlinked files, but it does on original one.

Environment

• Operating System: Ubuntu 20.04
• JDK version: 13.0.7
• Visual Studio Code version: 1.63.2
• Java extension version: 1.3.0

Steps To Reproduce

1. Create a sample java project with a .java file and introduce an error to it (e.g. use HashMap<String, String> without importing HashMap).
2. You should see HashMap underlined with an error HashMap cannot be resolved to a type
3. Create a symlink of the file to somewhere outside the project (in ubuntu: ln -s <path to original file> <path somewhere outside src/main/java structure>)
4. The new file won't have HashMap underlined

[rgrunber]

Very interesting. The symlink is getting resolved to the canonical file path so as far as the language server is concerned, the symlink gets nothing. If you try activating some code action on the symlink, you'll see the edits trigger and get applied to the canonical file (prior to saving).

I created a simple file /tmp/foo/src/org/example/Main.java and a symlink to it at /tmp/foo/Main.java. Even when opening up the symlink, I see :

[Trace - 10:24:16 AM] Received notification 'textDocument/publishDiagnostics'.
Params: {
    "uri": "file:///tmp/foo/src/org/example/Main.java",
    "diagnostics": [
        {
            "range": {
                "start": {
                    "line": 2,
                    "character": 8
                },
                "end": {
                    "line": 2,
                    "character": 15
                }
            },
            "severity": 1,
            "code": "16777218",
            "source": "Java",
            "message": "HashMap cannot be resolved to a type",
            "data": [
                "HashMap"
            ]
        }
    ]
}

This might be possible to support but would get tricky, and not sure how high of a priority it would be. If the original file has package org.example (valid), and you create a symlink outside src, then the package declaration should be default (empty). But we can't have both files existing in different states. So we probably want the canonical Uri in the language server, and simply do a path replacement (back to symlink) prior to the server response (f the document is referenced). This would ensure the symlink document receives the interactions when it is opened.