cmd/go: versioned package doc shows unexpected doc for stdlib #81670

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1. gabyhelp commented on Sep 22, 2026

   

   gabyhelp

   on Sep 22, 2026

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   Related Issues

   • cmd/go: go doc does not understand module versioning #54338 (closed)
   • cmd/go: unexpected output with go doc std #53446
   • x/pkgsite: don't set jsonv2 tag when showing encoding/json documentation #75170 (closed)
   • cmd/go,x/pkgsite/cmd/internal/doc: go doc -http should support @version #78459
   • x/tools/cmd/godoc: all std packages are treated as command #14447 (closed)
   • cmd/go: doc with package name broken outside modules #78896 (closed)
   • cmd/doc: go doc rsc.io/quote/v3 in module mode shows wrong import path #30778 (closed)
   • cmd/doc: go doc synctest.Wait shows wrong package #79988 (closed)
   • x/pkgsite: encoding/json: documentation mismatch between v1 and v2 for go1.26.5 #80325 (closed)
   • proposal: cmd/go: allow versioned go doc commands #73489 (closed)

   _{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}
2. prattmic commented on Sep 29, 2026

   

   prattmic

   on Sep 29, 2026

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   cc @golang/command-line
3. prattmic

   added

   NeedsInvestigationSomeone must examine and confirm this is a valid issue and not a duplicate of an existing one.Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.

   GoCommandcmd/gocmd/go

   on Sep 29, 2026
4. github-project-automation

   added this to Go Compiler / Runtime / Commandon Sep 29, 2026
5. dmitshur

   added this to the Backlog milestone on Oct 6, 2026
6. dmitshur

   added

   help wanted

   on Oct 6, 2026
7. matloob commented on Oct 6, 2026

   

   matloob

   on Oct 6, 2026

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   Sounds like we should just reject pkg@version syntax for stdlib packages.
8. hyangah commented on Oct 6, 2026

   

   hyangah

   on Oct 6, 2026

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   Or, exec GOTOOLCHAIN=go1.x.y go doc <pkg>?
9. hridhinvarkeyjoseph commented on Oct 6, 2026

   

   hridhinvarkeyjoseph

   on Oct 6, 2026

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   I looked into this, and I think the cause is in parseArgs in cmd/go/internal/doc/doc.go, not in the versioned load itself.

   For go doc encoding/json/v2@go1.19.0, importPkg calls loadVersioned, and load.PackagesAndErrorsOutsideModule already rejects it with argument must not be a package in the standard library. But that error is dropped: the single-argument path then falls into the loop that splits the argument at periods, and that loop calls loadPackage(ctx, loader, arg[0:period]), which loads the package without the version. For a standard library package that succeeds from GOROOT, so the current docs are printed. The same loop is reached for pkg.Symbol@version, so the version is ignored there too.

   Following @matloob's suggestion to reject @version for standard library packages, I'd like to send a fix that makes that loop use importPkg (versioned when a version is given), so the existing error is reported:

   go: encoding/json/v2@go1.19.0: argument must not be a package in the standard library
   

   with a script test in cmd/go/testdata/script. Does that direction sound right, or would you prefer the GOTOOLCHAIN approach?