Missing "unused imports" warnings when there's a compilation error

[brookhong]

textDocument/publishDiagnostics does not return unused imports in java.

Any chance to support this?

[fbricon]

Unused imports are absolutely reported. Except when a single Java file with no known classpath is opened, what we call a standalone java file.
If your project is Maven or Gradle-built, you should see unused import diagnostics, if you don't please provide a sample project reproducing the issue.

[brookhong]

This is weird.

I tried several other projects, unused imports are reported. But only for this one(I put it on github just now), it does not work.

I used in vim with YouCompleteMe, please see these two imports:

import java.util.ArrayList;
import java.util.List;

And here is the log from YCM:

2018-04-12 22:29:36,791 - DEBUG - RX: Received message: b'{"jsonrpc":"2.0","method":"textDocument/publishDiagnostics","params":{"uri":"file:///works/TestUnusedImports/src/main/java/com/halodu/HomeController.java","diagnostics":[{"range":{"start":{"line":23,"character":35},"end":{"line":23,"character":51}},"severity":2,"code":"570425421","source":"Java","message":"The value of the field HomeController.datastoreService is not used"},{"range":{"start":{"line":37,"character":8},"end":{"line":37,"character":14}},"severity":1,"code":"570425394","source":"Java","message":"LOGGER cannot be resolved"}]}}'

[fbricon]

The same project opens fine and report unused imports in vscode. Maybe @puremourning can help here?

[micbou]

Tried with the latest version of jdt.ls (YCM is currently on 0.15.0) and there are still no errors about unused imports. However, the command to organize imports is removing the unused imports so jdt.ls clearly knows that the imports are not used.

The same project opens fine and report unused imports in vscode.

Strange, I don't see any diagnostics about unused imports with vscode-java 0.22.0.

[brookhong]

I don't think YCM causes this, because I looked into the YCM log(which I had attached above), and here is the formatted received message from jdt.ls by ycmd.

{
    "jsonrpc": "2.0",
    "method": "textDocument/publishDiagnostics",
    "params": {
        "diagnostics": [
            {
                "code": "570425421",
                "message": "The value of the field HomeController.datastoreService is not used",
                "range": {
                    "end": {
                        "character": 51,
                        "line": 23
                    },
                    "start": {
                        "character": 35,
                        "line": 23
                    }
                },
                "severity": 2,
                "source": "Java"
            },
            {
                "code": "570425394",
                "message": "LOGGER cannot be resolved",
                "range": {
                    "end": {
                        "character": 14,
                        "line": 37
                    },
                    "start": {
                        "character": 8,
                        "line": 37
                    }
                },
                "severity": 1,
                "source": "Java"
            }
        ],
        "uri": "file:///works/TestUnusedImports/src/main/java/com/halodu/HomeController.java"
    }
}

[brookhong]

I also tried with latest eclipse.jdt.ls(dev build) with YCM, the message for textDocument/publishDiagnostics is same as above.

[brookhong]

I did some more investigation, and found that there might be some issue of eclipse.jdt.core.

A severity 1 error (LOGGER cannot be resolved) at line 38 is blocking two severity 2 (The import java.util.ArrayList is never used, The import java.util.List is never used) from being reported.

The same problem happens in eclipse.

diagnostics before line 38 commented out

{
    "jsonrpc": "2.0",
    "method": "textDocument/publishDiagnostics",
    "params": {
        "diagnostics": [
            {
                "code": "570425421",
                "message": "The value of the field HomeController.datastoreService is not used",
                "range": {
                    "end": {
                        "character": 51,
                        "line": 23
                    },
                    "start": {
                        "character": 35,
                        "line": 23
                    }
                },
                "severity": 2,
                "source": "Java"
            },
            {
                "code": "570425394",
                "message": "LOGGER cannot be resolved",
                "range": {
                    "end": {
                        "character": 14,
                        "line": 37
                    },
                    "start": {
                        "character": 8,
                        "line": 37
                    }
                },
                "severity": 1,
                "source": "Java"
            }
        ],
        "uri": "file:///works/TestUnusedImports/src/main/java/com/halodu/HomeController.java"
    }
}

diagnostics after line 38 commented out

{
    "jsonrpc": "2.0",
    "method": "textDocument/publishDiagnostics",
    "params": {
        "diagnostics": [
            {
                "code": "268435844",
                "message": "The import java.util.ArrayList is never used",
                "range": {
                    "end": {
                        "character": 26,
                        "line": 2
                    },
                    "start": {
                        "character": 7,
                        "line": 2
                    }
                },
                "severity": 2,
                "source": "Java"
            },
            {
                "code": "268435844",
                "message": "The import java.util.List is never used",
                "range": {
                    "end": {
                        "character": 21,
                        "line": 3
                    },
                    "start": {
                        "character": 7,
                        "line": 3
                    }
                },
                "severity": 2,
                "source": "Java"
            },
            {
                "code": "570425421",
                "message": "The value of the field HomeController.datastoreService is not used",
                "range": {
                    "end": {
                        "character": 51,
                        "line": 23
                    },
                    "start": {
                        "character": 35,
                        "line": 23
                    }
                },
                "severity": 2,
                "source": "Java"
            }
        ],
        "uri": "file:///works/TestUnusedImports/src/main/java/com/halodu/HomeController.java"
    }
}

[brookhong]

I reported the bug for eclipse.jdt.core -- https://bugs.eclipse.org/bugs/show_bug.cgi?id=533592
Feel free to close this if you'd like.

[fbricon]

Closing, according to https://bugs.eclipse.org/bugs/show_bug.cgi?id=533592#c2:

This is by design: as long as resolve errors are present, unused imports warning would in general not be reliable. So it's better to focus on definite and more severe errors first.