Debugger cannot display source for JDK/dependency classes (jdt:// frame URIs, sourceReference: 0)

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Avaliação

Dificuldade
4/5
Tempo estimado
3-5 dias
Facilidade para iniciantes
54/100
Tipo de issue
Bug
Clareza
Razoavelmente clara
Status de atividade
Ativa
Stack de tecnologia
java, rust
Domínio
devtools

Direção de pesquisa

The report traces the failure to the bundled Java debug adapter's StackTraceRequestHandler, JdtSourceLookUpProvider, and SourceRequestHandler; it does not identify those files in the repository. Start by locating the stack trace source construction and the existing source handle registration path. Check how jdt:// sources are represented in DAP frames, then verify that a source request can retrieve their content and that the frame receives a usable source reference.

Escrita pelo modelo de indexação a partir do texto da issue.

Descrição

Summary

Stepping into JDK or third-party library classes works (the frame shows up in the call stack), but no source can be displayed: the debug adapter reports every non-project frame's source as a jdt://contents/... URI with sourceReference: 0, which Zed cannot resolve. VS Code can render these URIs because the vscode-java extension registers a jdt:// content provider; Zed has no such provider and needs either an absolute file path or a non-zero DAP sourceReference to fetch source content.

Environment
Zed 1.27.0 (c84af5b99cbc366d675064e52b23664a015b6e35)
Java extension 6.8.30 (jdt.ls 1.63.0, com.microsoft.java.debug.plugin-0.53.2.jar)
OS Windows 11 (10.0.26300) x64
JDK Temurin 25.0.2+10 (%JAVA_HOME%\lib\src.zip present)
Project minimal Maven project, maven.compiler.release=17, dependency commons-lang3:3.17.0
Repro

src/main/java/demo/Main.java:

package demo;

import org.apache.commons.lang3.StringUtils;

public class Main {
    public static void main(String[] args) {
        String pretty = StringUtils.capitalize("world"); // breakpoint here, then Step Into (F11)
        System.out.println(pretty);
    }
}

.zed/debug.json:

[
  {
    "label": "demo: debug main",
    "adapter": "Java",
    "request": "launch",
    "mainClass": "demo.Main",
    "cwd": "$ZED_WORKTREE_ROOT",
    "stopOnEntry": true
  }
]

Step Into on the StringUtils.capitalize line: the call stack correctly gains a StringUtils.capitalize frame, but the editor shows nothing, and Zed.log fills with:

ERROR [crates::debugger_ui/src/session/running/stack_frame_list.rs:829] no absolute source path in stack frame 6, source: Some(Source {
  name: Some("StringUtils.java"),
  path: Some("jdt://contents/commons-lang3-3.17.0.jar/org.apache.commons.lang3/StringUtils.class?=zed-java-debug-demo/C:%5C/Users%5C/...%5C/commons-lang3-3.17.0.jar=/...=%3Corg.apache.commons.lang3(StringUtils.class"),
  source_reference: Some(0), ... })

Same behavior for JDK classes (java.lang.*, etc.): the frame appears, the source cannot be shown.

Root cause analysis

Inspecting com.microsoft.java.debug.plugin-0.53.2.jar (the bundled Microsoft java-debug server):

  1. JdtSourceLookUpProvider#getSourceFileURI(sourcePath, sourceName) returns a real file URI only when the lookup result is an IResource (workspace source file). Every class resolved as an IClassFile — i.e. anything from a jar or the JRT runtime, whether or not a sources jar / src.zip is attached — is turned into a jdt://contents/... URI by getFileURI(IClassFile).
  2. StackTraceRequestHandler emits that URI as Types.Source.path and leaves sourceReference at 0, so a DAP client has no way to fetch the content either. (The debugSupportOnDecompiledSource == ON branch only remaps line numbers; it does not set a sourceReference.)

So on any client other than VS Code (which resolves jdt:// via a content provider querying jdt.ls), library/JDK frames are source-less.

Things that do not fix it, for the record:

  • src.zip present / java.maven.downloadSources: true — the frame URI stays jdt:// even with sources attached; it only changes what content VS Code shows.
  • "sourcePaths": [...] in the launch config — the plugin's source lookup never consumes it (no directory source container is created from it).
  • stepFilters — not the issue here; stepping does enter the code.
Suggested fix

The adapter already has everything needed to serve this content over DAP: SourceRequestHandler implements the source request via IDebugAdapterContext#getSourceUri(int) → ISourceLookUpProvider#getSourceContents(String), and JdtSourceLookUpProvider#getSourceContents already returns source/decompiled content for jdt:// URIs.

So for frames whose resolved source is a jdt:// URI, it should additionally register the URI in sourceHandles and set source.sourceReference to that handle (optionally only when the client doesn't advertise jdt:// support). Then Zed — and any other non-VS Code DAP client — could display (and set breakpoints in, given supportsBreakpointLocationsRequest/line mapping) JDK and dependency sources.

Happy to provide logs or test a patched build on Windows.

Benchmark

For comparison, IntelliJ and VS Code (Extension Pack for Java) both display real or decompiled source for these frames.

Linguagem predominante
Rust
Estrelas
225
Forks
47
Merge médio
3h
PRs com merge (30d)
5

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