cmd/go: add loaderstate as field on mvsReqs

This change modifies the type `mvsReqs` to have an additional field to
store the current module loader state.  The field is used to break the
dependency on the global `modload.LoaderState` variable.

This commit is part of the overall effort to eliminate global
modloader state.

Change-Id: Id6bd96bc5de68bf327f9e78a778173634e1d15d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/711122
Reviewed-by: Michael Matloob <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: jitsu-net

src/cmd/go/internal/modload/buildlist.go

@@ -1319,7 +1319,7 @@ func tidyUnprunedRoots(loaderstate *State, ctx context.Context, mainModule modul
 
 	// Construct a build list with a minimal set of roots.
 	// This may remove or downgrade modules in altMods.
-	reqs := &mvsReqs{roots: keep}
+	reqs := &mvsReqs{loaderstate: loaderstate, roots: keep}
 	min, err := mvs.Req(mainModule, rootPaths, reqs)
 	if err != nil {
 		return nil, err
@@ -1445,7 +1445,7 @@ func updateUnprunedRoots(loaderstate *State, ctx context.Context, direct map[str
 
 	var roots []module.Version
 	for _, mainModule := range loaderstate.MainModules.Versions() {
-		min, err := mvs.Req(mainModule, rootPaths, &mvsReqs{roots: keep})
+		min, err := mvs.Req(mainModule, rootPaths, &mvsReqs{loaderstate: loaderstate, roots: keep})
 		if err != nil {
 			return rs, err
 		}

src/cmd/go/internal/modload/edit.go

@@ -532,7 +532,7 @@ func editRequirements(loaderstate *State, ctx context.Context, rs *Requirements,
 			}
 		}
 
-		roots, err = mvs.Req(loaderstate.MainModules.mustGetSingleMainModule(loaderstate), rootPaths, &mvsReqs{roots: roots})
+		roots, err = mvs.Req(loaderstate.MainModules.mustGetSingleMainModule(loaderstate), rootPaths, &mvsReqs{loaderstate: loaderstate, roots: roots})
 		if err != nil {
 			return nil, false, err
 		}

src/cmd/go/internal/modload/mvs.go

@@ -39,11 +39,12 @@ func cmpVersion(p string, v1, v2 string) int {
 // mvsReqs implements mvs.Reqs for module semantic versions,
 // with any exclusions or replacements applied internally.
 type mvsReqs struct {
-	roots []module.Version
+	loaderstate *State // TODO(jitsu): Is there a way we can not depend on the entire loader state?
+	roots       []module.Version
 }
 
 func (r *mvsReqs) Required(mod module.Version) ([]module.Version, error) {
-	if mod.Version == "" && LoaderState.MainModules.Contains(mod.Path) {
+	if mod.Version == "" && r.loaderstate.MainModules.Contains(mod.Path) {
 		// Use the build list as it existed when r was constructed, not the current
 		// global build list.
 		return r.roots, nil
@@ -53,7 +54,7 @@ func (r *mvsReqs) Required(mod module.Version) ([]module.Version, error) {
 		return nil, nil
 	}
 
-	summary, err := goModSummary(LoaderState, mod)
+	summary, err := goModSummary(r.loaderstate, mod)
 	if err != nil {
 		return nil, err
 	}
@@ -130,7 +131,7 @@ func previousVersion(loaderstate *State, ctx context.Context, m module.Version)
 	return module.Version{Path: m.Path, Version: "none"}, nil
 }
 
-func (*mvsReqs) Previous(m module.Version) (module.Version, error) {
+func (r *mvsReqs) Previous(m module.Version) (module.Version, error) {
 	// TODO(golang.org/issue/38714): thread tracing context through MVS.
-	return previousVersion(LoaderState, context.TODO(), m)
+	return previousVersion(r.loaderstate, context.TODO(), m)
 }