Exception occurred after sending textDocument/completion request.

[TherCN]

OS:Android 10
Java Version:17
Run Command:

export JDTLS_DIR=/sdcard/jdtls
java \
-Declipse.application=org.eclipse.jdt.ls.core.id1 \
-Dosgi.bundles.defaultStartLevel=4 \
-Declipse.product=org.eclipse.jdt.ls.core.product \
-Dosgi.checkConfiguration=true \
-Dosgi.sharedConfiguration.area=$JDTLS_DIR/config_linux \
-Dosgi.sharedConfiguration.area.readOnly=true \
-Dosgi.configuration.cascaded=true \
-Xms1G \
--add-modules=ALL-SYSTEM \
--add-opens \
java.base/java.util=ALL-UNNAMED \
--add-opens \
java.base/java.lang=ALL-UNNAMED \
-jar \
$JDTLS_DIR/plugins/org.eclipse.equinox.launcher_1.6.700.v20231214-2017.jar \
-data \
/storage/emulated/0/TestProject

The code to send the request is in: MainActivity.java

And I returned an exception when sending textDocument/completion, as down:

{
  "method": "window/logMessage",
  "jsonrpc": "2.0",
  "params": {
    "type": 1,
    "message": "Mar 25, 2024, 6:48:07 AM Problem with codeComplete for file:///storage/emulated/0/AppProjects/ADOFAI-Helper/src/main/java/thercn/adofai/helper/Main.java
Cannot invoke \"org.eclipse.lsp4j.CompletionCapabilities.getInsertTextMode()\" because the return value of \"org.eclipse.lsp4j.TextDocumentClientCapabilities.getCompletion()\" is null
java.lang.NullPointerException: Cannot invoke \"org.eclipse.lsp4j.CompletionCapabilities.getInsertTextMode()\" because the return value of \"org.eclipse.lsp4j.TextDocumentClientCapabilities.getCompletion()\" is null
	at org.eclipse.jdt.ls.core.internal.preferences.ClientPreferences.getCompletionItemInsertTextModeDefault(ClientPreferences.java:430)
	at org.eclipse.jdt.ls.core.internal.contentassist.CompletionProposalReplacementProvider.updateReplacement(CompletionProposalReplacementProvider.java:176)
	at org.eclipse.jdt.ls.core.internal.contentassist.CompletionProposalRequestor.initializeCompletionListItemDefaults(CompletionProposalRequestor.java:387)
	at org.eclipse.jdt.ls.core.internal.contentassist.CompletionProposalRequestor.getCompletionItems(CompletionProposalRequestor.java:283)
	at org.eclipse.jdt.ls.core.internal.contentassist.CompletionProposalRequestor.getCompletionItems(CompletionProposalRequestor.java:259)
	at org.eclipse.jdt.ls.core.internal.handlers.CompletionHandler.computeContentAssist(CompletionHandler.java:291)
	at org.eclipse.jdt.ls.core.internal.handlers.CompletionHandler.completion(CompletionHandler.java:121)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.completion(JDTLanguageServer.java:633)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.lambda$recursiveFindRpcMethods$0(GenericEndpoint.java:65)
	at org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint.notify(GenericEndpoint.java:152)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleNotification(RemoteEndpoint.java:220)
	at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:187)
	at org.eclipse.jdt.ls.core.internal.ParentProcessWatcher.lambda$1(ParentProcessWatcher.java:144)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:194)
	at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:94)
	at org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:113)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
	at java.base/java.lang.Thread.run(Thread.java:833)
"
  }
}

I tried this problem in versions 1.32.0 and 1.33.0 and 1.34.0snapshot respectively. How can I solve it?

[rgrunber]

I think this is actually a bug in our implementation that we should be fixing. According to the spec :

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocumentClientCapabilities

/**
   * Capabilities specific to the `textDocument/completion` request.
 */
completion?: CompletionClientCapabilities;

That question mark indicates the value is optional and need not be defined.

However, we're clearly accessing it without checking whether it exists (line 430) :

eclipse.jdt.ls/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/preferences/ClientPreferences.java

Lines 421 to 431 in df60479

	public boolean isCompletionItemInsertTextModeSupport(InsertTextMode insertMode) {
	return v3supported
	&& capabilities.getTextDocument().getCompletion() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem().getInsertTextModeSupport() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem().getInsertTextModeSupport().getValueSet().contains(insertMode);
	}
	public InsertTextMode getCompletionItemInsertTextModeDefault() {
	return capabilities.getTextDocument().getCompletion().getInsertTextMode();
	}

The lines immediately above show the right way to do it.

As a workaround, @TherCN , could you try setting defining :

JSONObject completionCapabilities = new JSONObject();
textCapabilities.put("completion", completionCapabilities);

at https://github.com/TherCN/LSPClient-Example/blob/main/app/src/main/java/com/example/MainActivity.java#L305 and see if that temporarily fixes it ?

[TherCN]

我认为这实际上是我们实施中的一个错误，我们应该修复。根据规范：

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specation/#textDocumentClientCapability

/**
   * Capabilities specific to the `textDocument/completion` request.
 */
completion?: CompletionClientCapabilities;

该问号表示该值是可选的，不需要定义。

然而，我们显然是在访问它而不检查它是否存在（第 430 行）：

eclipse.jdt.ls/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/preferences/ClientPreferences.java

Lines 421 to 431 in df60479

	public boolean isCompletionItemInsertTextModeSupport(InsertTextMode insertMode) {
	return v3supported
	&& capabilities.getTextDocument().getCompletion() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem().getInsertTextModeSupport() != null
	&& capabilities.getTextDocument().getCompletion().getCompletionItem().getInsertTextModeSupport().getValueSet().contains(insertMode);
	}
	public InsertTextMode getCompletionItemInsertTextModeDefault() {
	return capabilities.getTextDocument().getCompletion().getInsertTextMode();
	}

上面的几行显示了正确的方法。

作为解决方法，@TherCN，你可以尝试设置定义：

JSONObject completionCapabilities = new JSONObject();
textCapabilities.put("completion", completionCapabilities);

在https://github.com/TherCN/LSPClient-Example/blob/main/app/src/main/java/com/example/MainActivity.java#L305看看是否可以暂时修复它？

Thank you for your help. After I added the code, it didn't return an exception, but it didn't return a completion request either.

[rgrunber]

Would you be able to attach a log of the client requests that are made to the server as well as how the server responds ? The client would need to at least call initialize, followed by didOpen (on the Java file URI) prior to calling completion.

[TherCN]

Would you be able to attach a log of the client requests that are made to the server as well as how the server responds ? The client would need to at least call initialize, followed by didOpen (on the Java file URI) prior to calling completion.

LSPClient.log

[TherCN]

Would you be able to attach a log of the client requests that are made to the server as well as how the server responds ? The client would need to at least call initialize, followed by didOpen (on the Java file URI) prior to calling completion.

I added the id when I sent the request, and the completion request has been successfully returned. I will close this issue soon.

[rgrunber]

Good catch. Yeah according to https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#requestMessage , id is required.

In terms of debugging such issues in the future, you could start the language server to have it listening for a debugger, connect to it remotely so that you'd be able to see what's going wrong. I mention this in #2313 (comment) . This would have probably allowed you to debug where the id failure was occuring in https://github.com/eclipse-lsp4j/lsp4j/blob/32aac26422a93019c197f6f7d92349bee609f2d9/org.eclipse.lsp4j.jsonrpc/src/main/java/org/eclipse/lsp4j/jsonrpc/json/StreamMessageProducer.java#L80 .

To do this just make sure you add something like -agentlib:jdwp=transport=dt_socket,server=y,address=8000 to the virtual machine arguments of the language server startup. Since you're using the helper script, that, would be --jvm-arg="-agentlib:jdwp=transport=dt_socket,server=y,address=8000" . Then you can just connect to port 8000 as a remote Java debug session and as long you have JDT-LS and it's target platform in your workspace, it should be possible to debug.