[dev.cmdgo] all: merge master (c2f96e6) into dev.cmdgo

[gostls13.git] / src / cmd / go / internal / modload / buildlist.go

diff --git a/src/cmd/go/internal/modload/buildlist.go b/src/cmd/go/internal/modload/buildlist.go
index 4fbe563cb832c911bfff31dbb58162660eb5d302..9989bb5b2a47e4afe137e9fa4018edd1bccd9e71 100644 (file)
--- a/src/cmd/go/internal/modload/buildlist.go
+++ b/src/cmd/go/internal/modload/buildlist.go
@@ -196,6 +196,19 @@ func (rs *Requirements) rootSelected(path string) (version string, ok bool) {
        return "", false
 }
 
+// hasRedundantRoot returns true if the root list contains multiple requirements
+// of the same module or a requirement on any version of the main module.
+// Redundant requirements should be pruned, but they may influence version
+// selection.
+func (rs *Requirements) hasRedundantRoot() bool {
+       for i, m := range rs.rootModules {
+               if MainModules.Contains(m.Path) || (i > 0 && m.Path == rs.rootModules[i-1].Path) {
+                       return true
+               }
+       }
+       return false
+}
+
 // Graph returns the graph of module requirements loaded from the current
 // root modules (as reported by RootModules).
 //
@@ -897,6 +910,12 @@ func updateLazyRoots(ctx context.Context, direct map[string]bool, rs *Requiremen
                // and (trivially) version.
 
                if !rootsUpgraded {
+                       if cfg.BuildMod != "mod" {
+                               // The only changes to the root set (if any) were to remove duplicates.
+                               // The requirements are consistent (if perhaps redundant), so keep the
+                               // original rs to preserve its ModuleGraph.
+                               return rs, nil
+                       }
                        // The root set has converged: every root going into this iteration was
                        // already at its selected version, although we have have removed other
                        // (redundant) roots for the same path.