x/tools/go/packages: NeedDeps has no effect #56633
Description
The documentation for the NeedDeps field is unclear. It says:
// NeedDeps adds the fields requested by the LoadMode in the packages in Imports.
I think perhaps the idea might be more clearly expressed as:
// NeedDeps causes all Packages transitively reachable through
// the Imports map to also be populated according to the LoadMode.
but that isn't what actually happens. Observe:
xtools$ cat main.go
package main
import (
"fmt"
"log"
"golang.org/x/tools/go/packages"
)
func main() {
cfg := &packages.Config{
Mode: packages.NeedImports |
packages.NeedCompiledGoFiles |
//packages.NeedDeps | // try with and without this line
0,
}
pkgs, err := packages.Load(cfg, "runtime")
if err != nil {
log.Fatalf("load: %v", err)
}
packages.Visit(pkgs, nil, func(p *packages.Package) {
fmt.Println(p, len(p.CompiledGoFiles))
})
}
xtools$ go run ./main.go > with
# Now uncomment the NeedDeps line.
xtools$ go run ./main.go > without
xtools$ diff with without
xtools$
# nothing
In other words, the NeedDeps flag seems to have no effect when the NeedImports flag is set. And If you remove NeedImports, only a single package is reported, regardless of NeedDeps. It's as if the flag has no effect at all.
I would expect the following behaviors:
- Imports=true, deps=true: import graph fully populated according to mode bits
- imports=true, deps=false: import map is populated to depth 1; dependencies may be stubs.
- imports=false: import map is nil. Deps flag has no effect.