No auto-completion, no marking of compilation errors, etc.

I've done Clean Java Language Server Workspace, activated the "heavyweight mode" and waited for Java: Ready, but the extension still barely offers any support. Stack traces from the logs:

[Error - 11:33:40 AM] Request textDocument/codeAction failed.
  Message: Internal error.
  Code: -32603 
java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.jdt.core.IMethod.getCompilationUnit()" because "iMethod" is null
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.jdt.core.IMethod.getCompilationUnit()" because "iMethod" is null
	at org.eclipse.jdt.internal.corext.refactoring.code.makestatic.InitialConditionsChecker.checkSourceAvailable(InitialConditionsChecker.java:181)
	at org.eclipse.jdt.internal.corext.refactoring.code.MakeStaticRefactoring.checkInitialConditions(MakeStaticRefactoring.java:127)
	at org.eclipse.jdt.ls.core.internal.corrections.RefactorProcessor.getMakeMethodStaticRefactoringProposal(RefactorProcessor.java:1189)
	at org.eclipse.jdt.ls.core.internal.corrections.RefactorProcessor.getProposals(RefactorProcessor.java:228)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:221)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

java.util.concurrent.CompletionException: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 1
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 1
	at org.eclipse.jdt.internal.corext.fix.AddMissingMethodDeclarationFixCore$AddMissingMethodDeclarationProposalOperation.rewriteAST(AddMissingMethodDeclarationFixCore.java:241)
	at org.eclipse.jdt.internal.corext.fix.CompilationUnitRewriteOperationsFixCore.createChange(CompilationUnitRewriteOperationsFixCore.java:123)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAddMissingMethodDeclarationProposal(QuickAssistProcessor.java:1459)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAssists(QuickAssistProcessor.java:237)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:233)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

SEVERE: Internal error: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
java.util.concurrent.CompletionException: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
	at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.IndexOutOfBoundsException: Index 0 out of bounds for length 0
	at java.base/jdk.internal.util.Preconditions.outOfBounds(Unknown Source)
	at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Unknown Source)
	at java.base/jdk.internal.util.Preconditions.checkIndex(Unknown Source)
	at java.base/java.util.Objects.checkIndex(Unknown Source)
	at java.base/java.util.ArrayList.get(Unknown Source)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getTryWithResourceProposals(QuickAssistProcessor.java:1014)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getTryWithResourceProposals(QuickAssistProcessor.java:936)
	at org.eclipse.jdt.ls.core.internal.text.correction.QuickAssistProcessor.getAssists(QuickAssistProcessor.java:238)
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionHandler.getCodeActionCommands(CodeActionHandler.java:233)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$15(JDTLanguageServer.java:775)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

pre-release extension version 1.43.2025061908

Version: 1.101.1 (user setup)
Commit: 18e3a1ec544e6907be1e944a94c496e302073435
Date: 2025-06-18T13:35:12.605Z
Electron: 35.5.1
ElectronBuildId: 11727614
Chromium: 134.0.6998.205
Node.js: 22.15.1
V8: 13.4.114.21-electron.0
OS: Windows_NT x64 10.0.22631

報告された CodeActionHandler のパスと 3 つのスタックトレースから始め、RefactorProcessor、QuickAssistProcessor、JDTLanguageServer を追跡します。記載された VS Code と拡張機能のバージョンで失敗を再現し、その後、影響を受けるコードアクションのフローを特定します。これらの内部エラーが解決され、報告されたセットアップで補完とコンパイルエラーのサポートが機能すれば完了です。