cmd/go/internal/modload: compute direct in workspace mode

The Requirements structure, which represents the root level requirements
of the module graph also has a 'direct' field which contains the set of
direct dependencies of a module.

Before this change, in workspace mode, the direct field was not set on
the Requirements structure. This change sets direct in the two places
it's needed: when initializing Requirements from the workspace's mod
files and when updating Requirements based on imports.

When initializing Requirements from the workspace's mod files, this
change will use the 'indirect' comments in those mod files to record the
set of direct modules passed to the Requirements.

There is a loop in updateRequirements where we consider the imports of
the packages we loaded from the main module to make sure that all those
imported packages' modules are required.  The loop also updates direct
for each of those modules (which have at least one package directly
imported by the main modules).  Before this change, in the workspace
case we continued early from the loop and didn't proceed to the code
where direct is computed. This change fixes that.

Fixes #66789

Change-Id: I2b497fbf28c2197e8ba8e8ca5314c1a720f16364
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest,gotip-windows-amd64-longtest
Reviewed-on: https://go-review.googlesource.com/c/go/+/580256
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

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

@@ -795,13 +795,13 @@ func updateRoots(ctx context.Context, direct map[string]bool, rs *Requirements,
 	case pruned:
 		return updatePrunedRoots(ctx, direct, rs, pkgs, add, rootsImported)
 	case workspace:
-		return updateWorkspaceRoots(ctx, rs, add)
+		return updateWorkspaceRoots(ctx, direct, rs, add)
 	default:
 		panic(fmt.Sprintf("unsupported pruning mode: %v", rs.pruning))
 	}
 }
 
-func updateWorkspaceRoots(ctx context.Context, rs *Requirements, add []module.Version) (*Requirements, error) {
+func updateWorkspaceRoots(ctx context.Context, direct map[string]bool, rs *Requirements, add []module.Version) (*Requirements, error) {
 	if len(add) != 0 {
 		// add should be empty in workspace mode because workspace mode implies
 		// -mod=readonly, which in turn implies no new requirements. The code path
@@ -812,7 +812,7 @@ func updateWorkspaceRoots(ctx context.Context, rs *Requirements, add []module.Ve
 		// return an error.
 		panic("add is not empty")
 	}
-	return rs, nil
+	return newRequirements(workspace, rs.rootModules, direct), nil
 }
 
 // tidyPrunedRoots returns a minimal set of root requirements that maintains the

src/cmd/go/internal/modload/init.go

@@ -1318,6 +1318,7 @@ func requirementsFromModFiles(ctx context.Context, workFile *modfile.WorkFile, m
 			toolchain = workFile.Toolchain.Name
 		}
 		roots = appendGoAndToolchainRoots(roots, goVersion, toolchain, direct)
+		direct = directRequirements(modFiles)
 	} else {
 		pruning = pruningForGoVersion(MainModules.GoVersion())
 		if len(modFiles) != 1 {
@@ -1339,6 +1340,18 @@ const (
 	withToolchainRoot                  = true
 )
 
+func directRequirements(modFiles []*modfile.File) map[string]bool {
+	direct := make(map[string]bool)
+	for _, modFile := range modFiles {
+		for _, r := range modFile.Require {
+			if !r.Indirect {
+				direct[r.Mod.Path] = true
+			}
+		}
+	}
+	return direct
+}
+
 func rootsFromModFile(m module.Version, modFile *modfile.File, addToolchainRoot addToolchainRoot) (roots []module.Version, direct map[string]bool) {
 	direct = make(map[string]bool)
 	padding := 2 // Add padding for the toolchain and go version, added upon return.

src/cmd/go/internal/modload/load.go

@@ -1375,10 +1375,7 @@ func (ld *loader) updateRequirements(ctx context.Context) (changed bool, err err
 						Module:       dep.mod,
 					}
 				}
-				continue
-			}
-
-			if pkg.err == nil && cfg.BuildMod != "mod" {
+			} else if pkg.err == nil && cfg.BuildMod != "mod" {
 				if v, ok := rs.rootSelected(dep.mod.Path); !ok || v != dep.mod.Version {
 					// dep.mod is not an explicit dependency, but needs to be.
 					// Because we are not in "mod" mode, we will not be able to update it.

src/cmd/go/testdata/script/mod_list_direct_work.txt

@@ -0,0 +1,76 @@
+# Test that ModuleDirect.Public is correctly set on go list output.
+# This is a regression test for issue #66789.
+
+# In this test, the workspace contains modules example.com/a and
+# example.com/b. Module example.com/a has a direct requirement
+# on rsc.io/sampler, and an indirect requirement on golang.org/x/text
+# through rsc.io/isampler. Module example.com/b has a direct
+# requirement on example.com/c which is incorrectly marked as indirect
+# in module example.com/b's go.mod file.
+
+# Check that go list -m processes the indirect annotations in the
+# go.mod file.
+go list -f '{{.Path}} {{.Indirect}}' -m all
+stdout 'example.com/a false'
+stdout 'example.com/b false'
+stdout 'rsc.io/sampler false'
+stdout 'golang.org/x/text true'
+stdout 'example.com/c true' # Uses the information in go.mod without checking imports.
+
+# Check that 'go list all' correctly populates "indirect" module annotation.
+go list -f '{{.ImportPath}} {{with .Module}}{{.Indirect}}{{end}}' all
+stdout 'example.com/a false'
+stdout 'example.com/b false'
+stdout 'rsc.io/sampler false'
+stdout 'golang.org/x/text/language true'
+stdout 'example.com/c false'
+
+-- go.work --
+go 1.23
+
+use ./a
+use ./b
+-- a/go.mod --
+module example.com/a
+
+go 1.23
+
+require rsc.io/sampler v1.2.1
+
+require golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c // indirect
+-- a/a.go --
+package a
+
+import "rsc.io/sampler"
+
+func A() string {
+    return sampler.Hello()
+}
+-- b/go.mod --
+module example.com/b
+
+go 1.23
+
+// The indrect comment below is inaccurate. Its purpose
+// is to test that it is corrected when enough packages
+// are loaded to correct it.
+
+require example.com/c v1.0.0 // indirect
+
+replace example.com/c => ../c
+-- b/b.go --
+package b
+
+import "example.com/c"
+
+func B() {
+    c.C()
+}
+-- c/go.mod --
+module example.com/c
+
+go 1.23
+-- c/c.go --
+package c
+
+func C() {}