Golang x/tools/gopls/internal/cache: nil deref in modindex.Index.Lookup

#!stacks
"sigpanic" && "modindex.(*Index).Lookup" && "cache.(*goplsSource).resolveCacheReferences"

Issue created by stacks.

func (s *goplsSource) resolveCacheReferences(missing imports.References) ([]*result, error) {
    ix, err := s.S.view.ModcacheIndex()
    if err != nil {
        event.Error(s.ctx, "resolveCacheReferences", err)  <----------- missing return
    }

    found := make(map[string]*result)
    for pkg, nms := range missing {
        var ks []string
        for k := range nms {
            ks = append(ks, k)
        }
        cs := ix.LookupAll(pkg, ks...) // map[importPath][]Candidate        <-------- panics within here

This stack sKaGhw was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x153
• runtime.panicmem:=262,+0x2ff
• runtime.sigpanic:+19,+0x2cc
• golang.org/x/tools/internal/modindex.(*Index).Lookup:+1,+0x38
• golang.org/x/tools/internal/modindex.(*Index).LookupAll:+5,+0x9f
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).resolveCacheReferences:+12,+0x16b
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).ResolveReferences:+16,+0x143
• golang.org/x/tools/internal/imports.addExternalCandidates:+4,+0x97
• golang.org/x/tools/internal/imports.getFixesWithSource:+73,+0x2df
• golang.org/x/tools/internal/imports.FixImports:+12,+0x13f
• golang.org/x/tools/gopls/internal/golang.computeImportEdits:+24,+0x20f
• golang.org/x/tools/gopls/internal/golang.allImportsFixes.func1:+1,+0x4b
• golang.org/x/tools/gopls/internal/cache.(*importsState).runProcessEnvFunc:+42,+0x2e3
• golang.org/x/tools/gopls/internal/cache.(*Snapshot).RunProcessEnvFunc:=414,+0xbf
• golang.org/x/tools/gopls/internal/golang.allImportsFixes:+4,+0x70
• golang.org/x/tools/gopls/internal/golang.(*allImportsFixesResult).init:+1,+0x43
• golang.org/x/tools/gopls/internal/golang.lazyInit[...]:+8,+0xa3
• golang.org/x/tools/gopls/internal/golang.sourceOrganizeImports:+1,+0x43

golang.org/x/tools/gopls@v0.19.0-pre.2 go1.24.3 darwin/arm64 other,vscode (1)

Dups: nSR9Wg x4Uhuw

Comment From: adonovan

The fix may be as simple as a return statement. Whatever it is, let's cherrypick it into rc3.

Comment From: adonovan

This stack nSR9Wg was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x167
• runtime.panicmem:=262,+0x358
• runtime.sigpanic:+19,+0x328
• golang.org/x/tools/internal/modindex.(*Index).Lookup:+1,+0x4d
• golang.org/x/tools/internal/modindex.(*Index).LookupAll:+5,+0xc8
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).resolveCacheReferences:+12,+0x1d4
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).ResolveReferences:+16,+0x14c
• golang.org/x/tools/internal/imports.addExternalCandidates:+4,+0xbc
• golang.org/x/tools/internal/imports.getFixesWithSource:+73,+0x476
• golang.org/x/tools/internal/imports.FixImports:+12,+0x1cd
• golang.org/x/tools/gopls/internal/golang.computeImportEdits:+24,+0x251
• golang.org/x/tools/gopls/internal/golang.allImportsFixes.func1:+1,+0x49
• golang.org/x/tools/gopls/internal/cache.(*importsState).runProcessEnvFunc:+42,+0x333
• golang.org/x/tools/gopls/internal/cache.(*Snapshot).RunProcessEnvFunc:=414,+0x106
• golang.org/x/tools/gopls/internal/golang.allImportsFixes:+4,+0x93
• golang.org/x/tools/gopls/internal/golang.(*allImportsFixesResult).init:+1,+0x4f
• golang.org/x/tools/gopls/internal/golang.lazyInit[...]:+8,+0xa5
• golang.org/x/tools/gopls/internal/golang.sourceOrganizeImports:+1,+0x46

golang.org/x/tools/gopls@v0.19.0-pre.2 go1.24.3 linux/amd64 other,vscode (1)

This stack x4Uhuw was reported by telemetry:

• crash/crash
• runtime.gopanic:+69,+0x167
• runtime.panicmem:=262,+0x358
• runtime.sigpanic:+19,+0x328
• golang.org/x/tools/internal/modindex.(*Index).Lookup:+1,+0x4d
• golang.org/x/tools/internal/modindex.(*Index).LookupAll:+5,+0xc8
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).resolveCacheReferences:+12,+0x1d4
• golang.org/x/tools/gopls/internal/cache.(*goplsSource).ResolveReferences:+16,+0x14c
• golang.org/x/tools/internal/imports.addExternalCandidates:+4,+0xbc
• golang.org/x/tools/internal/imports.getFixesWithSource:+73,+0x476
• golang.org/x/tools/internal/imports.FixImports:+12,+0x1cd
• golang.org/x/tools/gopls/internal/golang.computeImportEdits:+24,+0x251
• golang.org/x/tools/gopls/internal/golang.allImportsFixes.func1:+1,+0x49
• golang.org/x/tools/gopls/internal/cache.(*importsState).runProcessEnvFunc:+42,+0x333
• golang.org/x/tools/gopls/internal/cache.(*Snapshot).RunProcessEnvFunc:=414,+0x106
• golang.org/x/tools/gopls/internal/golang.allImportsFixes:+4,+0x93
• golang.org/x/tools/gopls/internal/golang.(*allImportsFixesResult).init:+1,+0x4f
• golang.org/x/tools/gopls/internal/golang.lazyInit[...]:+8,+0xa5
• golang.org/x/tools/gopls/internal/golang.quickFix:+7,+0x50

golang.org/x/tools/gopls@v0.19.0-pre.2 go1.24.2 linux/amd64 vscode (5)
golang.org/x/tools/gopls@v0.19.0-pre.2 go1.24.3 linux/amd64 other,vscode (37)

Comment From: gabyhelp

Related Issues

• x/tools/gopls: nil deref panic in go.test code action #72907 (closed)
• x/tools/gopls: nil deref in 'go vendor' Snapshot.GoCommandInvocation #73891
• x/tools/gopls: nil panic in types.Package.Path while writing export data (internal/gcimporter) #73854
• x/tools/gopls: panic after failed PosRange in xrefs.Index #67704
• x/tools/gopls: "package name is %q, want %q" bug in typeCheckBatch.importPackage #64235
• x/tools/gopls: bug in analysis importer reported by telemetry #64236 (closed)
• x/tools/gopls: xrefs.Index panics after "can't fail" pgf.PosRange #70446 (closed)
• x/tools/gopls: nil deref in Exporter.ProcessEvent #71928
• x/tools/gopls: CodeAction: nil panic in findMatchingDiagnostics #71028 (closed)
• x/tools/gopls: imports.ApplyFixes panics with "invalid line number %d (should be \< %d)" #73587 (closed)

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Comment From: gopherbot

Change https://go.dev/cl/680258 mentions this issue: gopls/internal/cache: add missing error check