Error on hover: lllegal argument, contents must be defined

[aeschli]

v0.4.0

• in VSCode, create a sample project and add the file

package com.aeschli.testapp;

public class TestHelper {
    public static boolean compare(String a, String b) {
        return a.compareToIgnoreCase(b) == 0;
    }
}

• move the mouse over boolean
• the dev tools console shows

    at new e (/usr/share/code-insiders/resources/app/out/vs/workbench/node/extensionHostProcess.js:4:227228)
    at asHover (/home/aeschli/.vscode-insiders/extensions/redhat.java-0.4.0/node_modules/vscode-languageclient/lib/protocolConverter.js:63:16)
e.onUnexpectedError @ workbench.main.js:29

The problem seems to be that the hover object sent across the line doesn't contain a 'contents' field.

[fbricon]

You created the project before or after opening vscode?

[aeschli]

I created it while it was open, but in the meantime also started VSCode again on the project.

[aeschli]

I think it's a bug on the Java language server side. If a location doesn't have any hover to show, send 'null' as result, not a hover without contents.

[fbricon]

Ok I can reproduce the issue.

I think we send a non null Hover because lsp4j would crap out otherwise, but I need to check

[fbricon]

@aeschli it's actually VS Code that doesn't like null results:

[Error - 10:49:50 AM] Request textDocument/hover failed.
Error: The received response has neither a result nor an error property.
    at handleInvalidMessage (/Users/fbricon/Dev/projects/vscode-java/node_modules/vscode-jsonrpc/lib/main.js:381:40)
    at StreamMessageReader.callback (/Users/fbricon/Dev/projects/vscode-java/node_modules/vscode-jsonrpc/lib/main.js:492:13)
    at StreamMessageReader.onData (/Users/fbricon/Dev/projects/vscode-java/node_modules/vscode-jsonrpc/lib/messageReader.js:199:18)
    at Socket.<anonymous> (/Users/fbricon/Dev/projects/vscode-java/node_modules/vscode-jsonrpc/lib/messageReader.js:166:19)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at readableAddChunk (_stream_readable.js:176:18)
    at Socket.Readable.push (_stream_readable.js:134:10)
    at Pipe.onread (net.js:551:20)

[aeschli]

Yes, it can be discussed where the bug is. From how I understand the spec, 'contents' is a required field for hover.
That said, I created microsoft/vscode-languageserver-node#207 to be tolerant in the language client.

[aeschli]

#214 (comment)
I guess you didn't pass in a result at all. The code there checks for undefined. I think it should be at least 'null'.

[fbricon]

Yes it was when I sent a null Hover result instead of an Hover result with null content (your initial report)