x/tools/gopls: panic in token.File.Name within PackageDocHTML (telemetry)

[adonovan]

#!stacks
"runtime.sigpanic" && "go/token.(*File).Name:=114" && "golang.PackageDocHTML:+12"

	for _, f := range pkg.Syntax() {
		fileMap[pkg.FileSet().File(f.Pos()).Name()] = f // panic
	}

Issue created by stacks.

This stack BQeQrg was reported by telemetry:

• gopls/bug
• golang.org/x/tools/gopls/internal/util/bug.report:+35
• golang.org/x/tools/gopls/internal/util/bug.Report:+1
• golang.org/x/tools/gopls/internal/server.(*server).initWeb.withPanicHandler.func10.1:+2
• runtime.gopanic:+50
• runtime.panicmem:=262
• runtime.sigpanic:+19
• go/token.(*File).Name:=114
• golang.org/x/tools/gopls/internal/golang.PackageDocHTML:+12
• golang.org/x/tools/gopls/internal/server.(*server).initWeb.func6:+40
• net/http.HandlerFunc.ServeHTTP:+1
• golang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func11:+10
• net/http.HandlerFunc.ServeHTTP:+1
• net/http.(*ServeMux).ServeHTTP:+14
• golang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func9:+10
• net/http.HandlerFunc.ServeHTTP:+1
• golang.org/x/tools/gopls/internal/server.(*server).initWeb.withPanicHandler.func10:+7

golang.org/x/tools/gopls@v0.16.2 go1.23.2 linux/amd64 neovim (1)

[gabyhelp]

Related Issues and Documentation

• x/tools/gopls: Hover: panic in lookupObjectByName #69616
• x/tools/gopls: crash in Hover (telemetry) #69362
• x/tools/gopls: recovered panic in RenderPackageDoc #66449 (closed)
• x/tools/gopls: "nil metadata for %q" panic in Snapshot.getPackageHandles (reported by telemetry) #66144
• x/tools/gopls: RenderPkgDoc crashes on go.starlark.net/starlark #67287 (closed)
• x/tools/gopls: automated issue report (crash) #66174 (closed)
• code.google.com/p/go.tools/cmd/godoc: Panic handling package listing #7557 (closed)
• x/tools/gopls: crash in signature help on error.Error #63578 (closed)
• x/tools/gopls: crash in packageReferences (reported by telemetry) #66250 (closed)
• x/tools/gopls: panic in internal/golang.activeParameter #69552 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[IlyasYOY]

@adonovan Hello! I guess I found a bug. May I contribute a fix?

I created empty file:

Then I called action:

After that I have the same stacktrace in my neovim log:

[START][2024-11-01 21:02:04] LSP logging initiated
[ERROR][2024-11-01 21:02:04] ...lsp/handlers.lua:623	"2024/11/01 21:02:04 imports fixes: allImportsFixes: /Users/ilyasyoy/Projects/IlyasYOY/main.go:1:2: expected ';', found 'EOF' (and 2 more errors)\n\tfile=\"/Users/ilyasyoy/Projects/IlyasYOY/main.go\"\n"
[ERROR][2024-11-01 21:02:05] .../vim/lsp/rpc.lua:770	"rpc"	"gopls"	"stderr"	"server.go:3489: http: panic serving 127.0.0.1:61794: runtime error: invalid memory address or nil pointer dereference\ngoroutine 128 [running]:\nnet/http.(*conn).serve.func1()\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:1947 +0xb0\npanic({0x101962300?, 0x102119110?})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/runtime/panic.go:785 +0x124\ngo/token.(*File).Name(...)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/go/token/position.go:114\ngolang.org/x/tools/gopls/internal/golang.PackageDocHTML({0x1015eb532, 0x1}, 0x14000499da0, {0x101a95c40, 0x1400051c8c0})\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/golang/pkgdoc.go:284 +0x160\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.func6({0x101a99798, 0x140001d0380}, 0x140000aac80)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:350 +0x27c\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0380?}, 0x5?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func11({0x101a99798, 0x140001d0380}, 0x140000aab40)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x1400050e178?, {0x101a99798?, 0x140001d0380?}, 0x10155f2dc?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0380}, 0x140000aab40)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func9({0x101a99798, 0x140001d0380}, 0x140000aaa00)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0380?}, 0x10?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.withPanicHandler.func10({0x101a99798?, 0x140001d0380?}, 0x140000c3b28?)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:537 +0x74\nnet/http.HandlerFunc.ServeHTTP(0x1400050e098?, {0x101a99798?, 0x140001d0380?}, 0x100f40504?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0380}, 0x140000aaa00)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\nnet/http.serverHandler.ServeHTTP({0x140005a3590?}, {0x101a99798?, 0x140001d0380?}, 0x6?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3210 +0xbc\nnet/http.(*conn).serve(0x140000ffc20, {0x101a9b0e8, 0x140005a2de0})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2092 +0x4fc\ncreated by net/http.(*Server).Serve in goroutine 200\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3360 +0x3dc\n"
[ERROR][2024-11-01 21:02:06] .../vim/lsp/rpc.lua:770	"rpc"	"gopls"	"stderr"	"server.go:3489: http: panic serving 127.0.0.1:61795: runtime error: invalid memory address or nil pointer dereference\ngoroutine 209 [running]:\nnet/http.(*conn).serve.func1()\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:1947 +0xb0\npanic({0x101962300?, 0x102119110?})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/runtime/panic.go:785 +0x124\ngo/token.(*File).Name(...)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/go/token/position.go:114\ngolang.org/x/tools/gopls/internal/golang.PackageDocHTML({0x1015eb532, 0x1}, 0x14000499da0, {0x101a95c40, 0x1400051c8c0})\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/golang/pkgdoc.go:284 +0x160\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.func6({0x101a99798, 0x140001d0460}, 0x140000aaf00)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:350 +0x27c\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0460?}, 0x5?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func11({0x101a99798, 0x140001d0460}, 0x140000aadc0)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x1400050e178?, {0x101a99798?, 0x140001d0460?}, 0x10155f2dc?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0460}, 0x140000aadc0)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func9({0x101a99798, 0x140001d0460}, 0x1400025c140)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0460?}, 0x10?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.withPanicHandler.func10({0x101a99798?, 0x140001d0460?}, 0x140004f5b28?)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:537 +0x74\nnet/http.HandlerFunc.ServeHTTP(0x1400050e098?, {0x101a99798?, 0x140001d0460?}, 0x100f40504?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0460}, 0x1400025c140)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\nnet/http.serverHandler.ServeHTTP({0x140004e6600?}, {0x101a99798?, 0x140001d0460?}, 0x6?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3210 +0xbc\nnet/http.(*conn).serve(0x140000ffcb0, {0x101a9b0e8, 0x140005a2de0})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2092 +0x4fc\ncreated by net/http.(*Server).Serve in goroutine 200\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3360 +0x3dc\n"
[ERROR][2024-11-01 21:02:06] .../vim/lsp/rpc.lua:770	"rpc"	"gopls"	"stderr"	"server.go:3489: http: panic serving 127.0.0.1:61796: runtime error: invalid memory address or nil pointer dereference\ngoroutine 187 [running]:\nnet/http.(*conn).serve.func1()\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:1947 +0xb0\npanic({0x101962300?, 0x102119110?})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/runtime/panic.go:785 +0x124\ngo/token.(*File).Name(...)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/go/token/position.go:114\ngolang.org/x/tools/gopls/internal/golang.PackageDocHTML({0x1015eb532, 0x1}, 0x14000499da0, {0x101a95c40, 0x1400051c8c0})\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/golang/pkgdoc.go:284 +0x160\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.func6({0x101a99798, 0x140001d0540}, 0x140000ab2c0)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:350 +0x27c\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0540?}, 0x5?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func11({0x101a99798, 0x140001d0540}, 0x140000ab180)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x1400050e178?, {0x101a99798?, 0x140001d0540?}, 0x10155f2dc?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0540}, 0x140000ab180)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.StripPrefix.func9({0x101a99798, 0x140001d0540}, 0x140000ab040)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2282 +0x228\nnet/http.HandlerFunc.ServeHTTP(0x0?, {0x101a99798?, 0x140001d0540?}, 0x10?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\ngolang.org/x/tools/gopls/internal/server.(*server).initWeb.withPanicHandler.func10({0x101a99798?, 0x140001d0540?}, 0x140004f5b28?)\n\t/Users/ilyasyoy/go/pkg/mod/golang.org/x/tools/gopls@v0.16.2/internal/server/server.go:537 +0x74\nnet/http.HandlerFunc.ServeHTTP(0x1400050e098?, {0x101a99798?, 0x140001d0540?}, 0x100f40504?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2220 +0x38\nnet/http.(*ServeMux).ServeHTTP(0x0?, {0x101a99798, 0x140001d0540}, 0x140000ab040)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2747 +0x1b4\nnet/http.serverHandler.ServeHTTP({0x140005a3bc0?}, {0x101a99798?, 0x140001d0540?}, 0x6?)\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3210 +0xbc\nnet/http.(*conn).serve(0x140003f5050, {0x101a9b0e8, 0x140005a2de0})\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:2092 +0x4fc\ncreated by net/http.(*Server).Serve in goroutine 200\n\t/opt/homebrew/Cellar/go/1.23.0/libexec/src/net/http/server.go:3360 +0x3dc\n"

I guess the fix might be here: /src/go/ast/ast.go#L1057 (or in tools code near the caller logic)

There is no package in the file so the documentation might not be generated.

[adonovan]

Thanks for explaining the input that caused the crash! There are actually two bugs here. The first is that the loop in PackageDocHTML should not assume that File.Pos() is valid, as it may not be for (e.g.) empty files; instead it should use File.FileStart. However, the second bug is that the parser fails to populate FileStart and FileEnd in the case of an empty file; I've filed that separately as #70162.

[gopherbot]

Change https://go.dev/cl/624437 mentions this issue: x/tools: fset.File(file.Pos()) -> fset.File(file.FileStart)