`NullpointerException` when `org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()`

[agreedSkiing]

When I do a save action and have format on save active or do a format document action by right clicking in the document i get these errors

Mar 11, 2025 8:04:11 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint fallbackResponseError
SEVERE: Internal error: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
    at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315)
    at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:649)
    at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:483)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:387)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1312)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1843)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1808)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:188)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
    at org.eclipse.jdt.ls.core.internal.handlers.CodeActionResolveHandler.resolve(CodeActionResolveHandler.java:52)
    at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$16(JDTLanguageServer.java:803)
    at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:646)
    ... 6 more

[Error - 8:04:11 AM] Request codeAction/resolve failed.
  Message: Internal error.
  Code: -32603 
java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
    at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315)
    at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:649)
    at java.base/java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:483)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:387)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1312)
    at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1843)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1808)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:188)
Caused by: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
    at org.eclipse.jdt.ls.core.internal.handlers.CodeActionResolveHandler.resolve(CodeActionResolveHandler.java:52)
    at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$16(JDTLanguageServer.java:803)
    at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:646)
    ... 6 more

Version

Name: Language Support for Java(TM) by Red Hat
Id: redhat.java
Description: Java Linting, Intellisense, formatting, refactoring, Maven/Gradle support and more...
Version: 1.40.0
Publisher: Red Hat
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=redhat.java

Visual studio code

Version: 1.97.2 (system setup)
Commit: e54c774e0add60467559eb0d1e229c6452cf8447
Date: 2025-02-12T23:20:35.343Z
Electron: 32.2.7
ElectronBuildId: 10982180
Chromium: 128.0.6613.186
Node.js: 20.18.1
V8: 12.8.374.38-electron.0
OS: Windows_NT x64 10.0.22631

Maven and java version

Apache Maven 3.9.6 (bc0240f3c744dd6b6ec2920b3cd08dcc295161ae)
Maven home: /home/eriase/.asdf/installs/maven/3.9.6
Java version: 21.0.3, vendor: Oracle Corporation, runtime: /home/eriase/.asdf/installs/java/oracle-21.0.3
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "5.15.167.4-microsoft-standard-wsl2", arch: "amd64", family: "unix"

Ubuntu version

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 24.04.2 LTS
Release:        24.04
Codename:       noble

Windows subsystem for linux

WSL-version: 2.3.26.0
Kernelversion: 5.15.167.4-1
WSLg-version: 1.0.65
MSRDC-version: 1.2.5620
Direct3D-version: 1.611.1-81528511
DXCore-version: 10.0.26100.1-240331-1435.ge-release
Windows-version: 10.0.22631.4890

Remote (windows subsystem for linux) settings

  "java.jdt.ls.java.home": "/home/eriase/.asdf/installs/java/oracle-21.0.3",

Workspace settings

{
    "[java]": {
        "editor.codeActionsOnSave": {
            "source.organizeImports": "always"
        },
        "editor.defaultFormatter": "redhat.java",
        "editor.tabSize": 2,
        "editor.insertSpaces": true,
        "editor.detectIndentation": false,
        "editor.formatOnSave": true
    },
    "java.format.settings.url": "eclipse-java-google-style.xml",
    "java.format.settings.profile": "GoogleStyle",
    "java.checkstyle.configuration": "google_checks.xml",
    "java.checkstyle.version": "10.21.2",
    "files.autoSave": "afterDelay",
    "files.autoSaveDelay": 1000,
    "java.saveActions.cleanup": true,
    "java.saveActions.organizeImports": true
}

[rgrunber]

I'm able to reproduce also. It happens specifically when there is nothing for the "organize imports" cleanup to perform.

[Info  - 15:19:32] Mar 18, 2025, 3:19:32 p.m. >> codeAction/resolve
Mar 18, 2025 3:22:22 P.M. org.eclipse.lsp4j.jsonrpc.RemoteEndpoint fallbackResponseError
SEVERE: Internal error: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
java.util.concurrent.CompletionException: java.lang.NullPointerException: Cannot invoke "org.eclipse.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" 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.lsp4j.WorkspaceEdit.getDocumentChanges()" because "edit" is null
	at org.eclipse.jdt.ls.core.internal.handlers.CodeActionResolveHandler.resolve(CodeActionResolveHandler.java:52)
	at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.lambda$16(JDTLanguageServer.java:798)
	at org.eclipse.jdt.ls.core.internal.BaseJDTLanguageServer.lambda$0(BaseJDTLanguageServer.java:87)
	... 7 more

At first I didn't believe this could be happening because the cleanups/formatting on save definitely don't activate the code action resolve workflow. But this actually what "editor.codeActionsOnSave" accomplishes. It's not a setting we provide, but it can interact with our code actions. Specifically, it will automatically apply all code actions whose kind is listed there.

The fix will likely be at https://github.com/eclipse-jdtls/eclipse.jdt.ls/blob/4ee0168c64e1430eac98e5ad255233a8c32dc87f/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/CodeActionResolveHandler.java#L51-L52 (as the stacktrace implies). We need to also check that the resulting edit is not null.