cmd/go/internal/modload: add a dormant depth type

This change adds the depth constants 'lazy' and 'eager', but leaves
the go117EnableLazyLoading constant set to false so that the depth in
effect is still always 'eager'.

The go117EnableLazyLoading constant can be toggled to true once the
module loader has been updated to maintain the lazy-loading invariants
in the go.mod file. In the meantime, this will allow me to
progressively replace uses of go117LazyTODO with real conditions and
locally toggle lazy-mode on to see which tests are still failing
(or which behaviors are missing test coverage).

For #36460

Change-Id: Ifd358265a3903a5000003c2072f28171f336e15c
Reviewed-on: https://go-review.googlesource.com/c/go/+/308515
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 5bff17e579..5de26c15e7 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -537,7 +537,7 @@ func pathInModuleCache(ctx context.Context, dir string, rs *Requirements) string
 		return path.Join(m.Path, filepath.ToSlash(sub)), true
 	}
 
-	if go117LazyTODO {
+	if rs.depth == lazy {
 		for _, m := range rs.rootModules {
 			if v, _ := rs.rootSelected(m.Path); v != m.Version {
 				continue // m is a root, but we have a higher root for the same path.
@@ -550,9 +550,9 @@ func pathInModuleCache(ctx context.Context, dir string, rs *Requirements) string
 		}
 	}
 
-	// None of the roots contained dir, or we're in eager mode and have already
-	// loaded the full module graph. Either way, check the full graph to see if
-	// the directory is a non-root dependency.
+	// None of the roots contained dir, or we're in eager mode and want to load
+	// the full module graph more aggressively. Either way, check the full graph
+	// to see if the directory is a non-root dependency.
 	//
 	// If the roots are not consistent with the full module graph, the selected
 	// versions of root modules may differ from what we already checked above.
@@ -1020,7 +1020,7 @@ func (ld *loader) updateRequirements(ctx context.Context) error {
 		}
 	}
 
-	rs, err := updateRoots(ctx, direct, ld.pkgs, rs)
+	rs, err := updateRoots(ctx, rs.depth, direct, ld.pkgs, rs)
 	if err == nil {
 		ld.requirements = rs
 	}