cmd/go: crash during loading in dirAndRoot (vendor-related)

[adonovan]

@samthanawalla encountered this crash while using the web-based VS Code with a Google VM as the backend.

The error indicates a crash propagated via gopls and go/packages up from the go command, specifically the dirAndRoot function:

// dirAndRoot returns the source directory and workspace root
// for the package p, guaranteeing that root is a path prefix of dir.
func dirAndRoot(path string, dir, root string) (string, string) {
	origDir, origRoot := dir, root
	dir = filepath.Clean(dir)
	root = filepath.Join(root, "src")
	if !str.HasFilePathPrefix(dir, root) || path != "command-line-arguments" && filepath.Join(root, path) != dir {
		// Look for symlinks before reporting error.
		dir = expandPath(dir)
		root = expandPath(root)
	}

	if !str.HasFilePathPrefix(dir, root) || len(dir) <= len(root) || dir[len(root)] != filepath.Separator || path != "command-line-arguments" && !build.IsLocalImport(path) && filepath.Join(root, path) != dir {
		debug.PrintStack()
		base.Fatalf("unexpected directory layout:\n"+
			"	import path: %s\n"+
			"	root: %s\n"+
			"	dir: %s\n"+
			"	expand root: %s\n"+
			"	expand dir: %s\n"+
			"	separator: %s",
			path,
			filepath.Join(origRoot, "src"),
			filepath.Clean(origDir),
			origRoot,
			origDir,
			string(filepath.Separator))
	}

	return dir, root
}

In addition the VS Code UI showed this truncated error:

Failed to run "go env env, -json, GOMOD": Command failed: /usr/lib/go...

Sorry there's not much to go on yet. I wonder whether the remote machine has as GOPACKAGESDRIVER env var (or $PATH executable).

[adonovan]

@hyangah The "failed to run go env" part appears to be from logic in vscode-go (in src/goModules.ts).

[adonovan]

We managed to get the complete stack and the actual values in the assertion failure:

Error loading workspace: packages.Load error: err: exit status 1: stderr:

goroutine 3373 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:24 +0x5e
runtime/debug.PrintStack()
	runtime/debug/stack.go:16 +0x13
cmd/go/internal/load.dirAndRoot({0xc00058ace1, 0x17}, {0xc000c31630, 0x4e}, {0xc000026187, 0x27})
	cmd/go/internal/load/pkg.go:1203 +0x4ad
cmd/go/internal/load.vendoredImportPath({0xc0005bb9c1, 0x4}, {0xc00058ace1, 0x17}, {0xc000c31630?, 0xc000224548?}, {0xc000026187?, 0x48?})
	cmd/go/internal/load/pkg.go:1231 +0x85
cmd/go/internal/load.resolveImportPath({0xc0005bb9c1, 0x4}, {0xc00058ace1, 0x17}, {0xc000c31630, 0x4e}, {0xc000026187, 0x27}, 0x9b?)
	cmd/go/internal/load/pkg.go:1183 +0x9e
cmd/go/internal/load.loadPackageData.func1()
	cmd/go/internal/load/pkg.go:905 +0x1ac
cmd/go/internal/par.(*Cache[...]).Do(0xbb0de0, {{0xc0005bb9c1, 0x4}, {0xc00058ace1, 0x17}, {0xc000c31630, 0x4e}, {0xc000026187, 0x27}, 0x0, ...}, ...)
	cmd/go/internal/par/work.go:160 +0x159
cmd/go/internal/load.loadPackageData({0xbab970, 0xf96260}, {0xc0005bb9c1, 0x4}, {0xc00058ace1, 0x17}, {0xc000c31630, 0x4e}, {0xc000026187, 0x27}, ...)
	cmd/go/internal/load/pkg.go:893 +0x38e
cmd/go/internal/load.(*preload).preloadImports.func1({0xc0005bb9c1?, 0x8?})
	cmd/go/internal/load/pkg.go:1115 +0x8b
created by cmd/go/internal/load.(*preload).preloadImports in goroutine 3883
	cmd/go/internal/load/pkg.go:1114 +0x265
unexpected directory layout:

import path: golang.org/x/mod/semver
root: /usr/local/google/home/samthanawalla/go/src
dir: /usr/local/google/home/samthanawalla/go/src/cmd/vendor/golang.org/x/mod/semver
expand root: /usr/local/google/home/samthanawalla/go
expand dir: /usr/local/google/home/samthanawalla/go/src/cmd/vendor/golang.org/x/mod/semver
separator: / 

it seems like the immediate problem is the "root + path = dir" invariant is violated because of a missing "vendor" segment.

cc @matloob

[bcmills]

I'm surprised that vendoredImportPath is being called at all: that's specific to GOPATH mode, which shouldn't be in use. 🤔

https://cs.opensource.google/go/go/+/master:src/cmd/go/internal/load/pkg.go;l=1177-1183;drc=b32ec6c961182e5bca6ae8420d6aa1204d7d2821

[matloob]

Yeah I think we should figure out why vendoredImportPath is being called. Sam, would you have time to do some debugging of this?

[samthanawalla]

Sure. I can try to debug the issue on my machine.

[samthanawalla]

We debugged this to be an issue with conflicting Go versions. I had one default installation of Go and one that I built from the github Repo.

This is what fixed it for me:

1. mv $HOME/go $HOME/w/go/
2. Copy the output of echo $PATH
3. Add this line to $HOME/.bashrc: export PATH=$HOME/go/bin:$HOME/w/go/bin:<what you copied from echo $PATH>
4. unset GOROOT and unset GOPATH.
5. Reload vscode

Optionally: go env -w GOMODCACHE=$HOME/w/go/pkg/mod

This fixed this issue and allowed gopls to work perfectly.