cmd/go: in 'go get', only load retractions for resolved versions

Previously, 'go get' loaded retractions for every module in the build
list, which took a long time and usually wasn't helpful.

This rolls forward CL 269019, which was reverted in CL 270521. The new
revision adds a call to modload.ListModules at the end of 'go get' to
ensure .info files are cached for everything in the build list.

Fixes #42185

Change-Id: I684f66c5e674384d5a0176fbc8317e5530b8a915
Reviewed-on: https://go-review.googlesource.com/c/go/+/270858
Trust: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/modget/get.go

@@ -419,20 +419,7 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 			pkgPatterns = append(pkgPatterns, q.pattern)
 		}
 	}
-	if len(pkgPatterns) > 0 {
+	r.checkPackagesAndRetractions(ctx, pkgPatterns)
-		// We skipped over missing-package errors earlier: we want to resolve
-		// pathSets ourselves, but at that point we don't have enough context
-		// to log the package-import chains leading to the error. Reload the package
-		// import graph one last time to report any remaining unresolved
-		// dependencies.
-		pkgOpts := modload.PackageOpts{
-			LoadTests:             *getT,
-			ResolveMissingImports: false,
-			AllowErrors:           false,
-		}
-		modload.LoadPackages(ctx, pkgOpts, pkgPatterns...)
-		base.ExitIfErrors()
-	}
 
 	// We've already downloaded modules (and identified direct and indirect
 	// dependencies) by loading packages in findAndUpgradeImports.
@@ -480,14 +467,20 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 	modload.WriteGoMod()
 	modload.DisallowWriteGoMod()
 
-	// Report warnings if any retracted versions are in the build list.
+	// Ensure .info files are cached for each module in the build list.
-	// This must be done after writing go.mod to avoid spurious '// indirect'
+	// This ensures 'go list -m all' can succeed later if offline.
-	// comments. These functions read and write global state.
+	// 'go get' only loads .info files for queried versions. 'go list -m' needs
+	// them to add timestamps to the output.
 	//
-	// TODO(golang.org/issue/40775): ListModules (called from reportRetractions)
+	// This is best effort since build commands don't need .info files to load
-	// resets modload.loader, which contains information about direct dependencies
+	// the build list.
-	// that WriteGoMod uses. Refactor to avoid these kinds of global side effects.
+	//
-	reportRetractions(ctx)
+	// TODO(golang.org/issue/40775): ListModules resets modload.loader, which
+	// contains information about direct dependencies that WriteGoMod uses.
+	// Refactor to avoid these kinds of global side effects.
+	if modload.HasModRoot() {
+		modload.ListModules(ctx, []string{"all"}, false, false, false)
+	}
 }
 
 // parseArgs parses command-line arguments and reports errors.
@@ -531,43 +524,6 @@ func parseArgs(ctx context.Context, rawArgs []string) []*query {
 	return queries
 }
 
-// reportRetractions prints warnings if any modules in the build list are
-// retracted.
-func reportRetractions(ctx context.Context) {
-	// Query for retractions of modules in the build list.
-	// Use modload.ListModules, since that provides information in the same format
-	// as 'go list -m'. Don't query for "all", since that's not allowed outside a
-	// module.
-	buildList := modload.LoadedModules()
-	args := make([]string, 0, len(buildList))
-	for _, m := range buildList {
-		if m.Version == "" {
-			// main module or dummy target module
-			continue
-		}
-		args = append(args, m.Path+"@"+m.Version)
-	}
-	listU := false
-	listVersions := false
-	listRetractions := true
-	mods := modload.ListModules(ctx, args, listU, listVersions, listRetractions)
-	retractPath := ""
-	for _, mod := range mods {
-		if len(mod.Retracted) > 0 {
-			if retractPath == "" {
-				retractPath = mod.Path
-			} else {
-				retractPath = "<module>"
-			}
-			rationale := modload.ShortRetractionRationale(mod.Retracted[0])
-			fmt.Fprintf(os.Stderr, "go: warning: %s@%s is retracted: %s\n", mod.Path, mod.Version, rationale)
-		}
-	}
-	if modload.HasModRoot() && retractPath != "" {
-		fmt.Fprintf(os.Stderr, "go: run 'go get %s@latest' to switch to the latest unretracted version\n", retractPath)
-	}
-}
-
 type resolver struct {
 	localQueries      []*query // queries for absolute or relative paths
 	pathQueries       []*query // package path literal queries in original order
@@ -594,9 +550,6 @@ type resolver struct {
 
 	work *par.Queue
 
-	queryModuleCache   par.Cache
-	queryPackagesCache par.Cache
-	queryPatternCache  par.Cache
 	matchInModuleCache par.Cache
 }
 
@@ -681,7 +634,7 @@ func (r *resolver) noneForPath(mPath string) (nq *query, found bool) {
 	return nil, false
 }
 
-// queryModule wraps modload.Query, substituting r.checkAllowedor to decide
+// queryModule wraps modload.Query, substituting r.checkAllowedOr to decide
 // allowed versions.
 func (r *resolver) queryModule(ctx context.Context, mPath, query string, selected func(string) string) (module.Version, error) {
 	current := r.initialSelected(mPath)
@@ -1217,7 +1170,7 @@ func (r *resolver) findAndUpgradeImports(ctx context.Context, queries []*query)
 		}
 
 		mu.Lock()
-		upgrades = append(upgrades, pathSet{pkgMods: pkgMods, err: err})
+		upgrades = append(upgrades, pathSet{path: path, pkgMods: pkgMods, err: err})
 		mu.Unlock()
 		return false
 	}
@@ -1544,6 +1497,87 @@ func (r *resolver) chooseArbitrarily(cs pathSet) (isPackage bool, m module.Versi
 	return false, cs.mod
 }
 
+// checkPackagesAndRetractions reloads packages for the given patterns and
+// reports missing and ambiguous package errors. It also reports loads and
+// reports retractions for resolved modules and modules needed to build
+// named packages.
+//
+// We skip missing-package errors earlier in the process, since we want to
+// resolve pathSets ourselves, but at that point, we don't have enough context
+// to log the package-import chains leading to each error.
+func (r *resolver) checkPackagesAndRetractions(ctx context.Context, pkgPatterns []string) {
+	defer base.ExitIfErrors()
+
+	// Build a list of modules to load retractions for. Start with versions
+	// selected based on command line queries.
+	//
+	// This is a subset of the build list. If the main module has a lot of
+	// dependencies, loading retractions for the entire build list would be slow.
+	relevantMods := make(map[module.Version]struct{})
+	for path, reason := range r.resolvedVersion {
+		relevantMods[module.Version{Path: path, Version: reason.version}] = struct{}{}
+	}
+
+	// Reload packages, reporting errors for missing and ambiguous imports.
+	if len(pkgPatterns) > 0 {
+		// LoadPackages will print errors (since it has more context) but will not
+		// exit, since we need to load retractions later.
+		pkgOpts := modload.PackageOpts{
+			LoadTests:             *getT,
+			ResolveMissingImports: false,
+			AllowErrors:           true,
+		}
+		matches, pkgs := modload.LoadPackages(ctx, pkgOpts, pkgPatterns...)
+		for _, m := range matches {
+			if len(m.Errs) > 0 {
+				base.SetExitStatus(1)
+				break
+			}
+		}
+		for _, pkg := range pkgs {
+			if _, _, err := modload.Lookup("", false, pkg); err != nil {
+				base.SetExitStatus(1)
+				if ambiguousErr := (*modload.AmbiguousImportError)(nil); errors.As(err, &ambiguousErr) {
+					for _, m := range ambiguousErr.Modules {
+						relevantMods[m] = struct{}{}
+					}
+				}
+			}
+			if m := modload.PackageModule(pkg); m.Path != "" {
+				relevantMods[m] = struct{}{}
+			}
+		}
+	}
+
+	// Load and report retractions.
+	type retraction struct {
+		m   module.Version
+		err error
+	}
+	retractions := make([]retraction, 0, len(relevantMods))
+	for m := range relevantMods {
+		retractions = append(retractions, retraction{m: m})
+	}
+	sort.Slice(retractions, func(i, j int) bool {
+		return retractions[i].m.Path < retractions[j].m.Path
+	})
+	for i := 0; i < len(retractions); i++ {
+		i := i
+		r.work.Add(func() {
+			err := modload.CheckRetractions(ctx, retractions[i].m)
+			if retractErr := (*modload.ModuleRetractedError)(nil); errors.As(err, &retractErr) {
+				retractions[i].err = err
+			}
+		})
+	}
+	<-r.work.Idle()
+	for _, r := range retractions {
+		if r.err != nil {
+			fmt.Fprintf(os.Stderr, "go: warning: %v\n", r.err)
+		}
+	}
+}
+
 // reportChanges logs resolved version changes to os.Stderr.
 func (r *resolver) reportChanges(queries []*query) {
 	for _, q := range queries {

src/cmd/go/internal/modload/build.go

@@ -123,13 +123,13 @@ func addRetraction(ctx context.Context, m *modinfo.ModulePublic) {
 		return
 	}
 
-	err := checkRetractions(ctx, module.Version{Path: m.Path, Version: m.Version})
+	err := CheckRetractions(ctx, module.Version{Path: m.Path, Version: m.Version})
-	var rerr *retractedError
+	var rerr *ModuleRetractedError
 	if errors.As(err, &rerr) {
-		if len(rerr.rationale) == 0 {
+		if len(rerr.Rationale) == 0 {
 			m.Retracted = []string{"retracted by module author"}
 		} else {
-			m.Retracted = rerr.rationale
+			m.Retracted = rerr.Rationale
 		}
 	} else if err != nil && m.Error == nil {
 		m.Error = &modinfo.ModuleError{Err: err.Error()}

src/cmd/go/internal/modload/modfile.go

@@ -59,7 +59,7 @@ func CheckAllowed(ctx context.Context, m module.Version) error {
 	if err := CheckExclusions(ctx, m); err != nil {
 		return err
 	}
-	if err := checkRetractions(ctx, m); err != nil {
+	if err := CheckRetractions(ctx, m); err != nil {
 		return err
 	}
 	return nil
@@ -85,9 +85,9 @@ type excludedError struct{}
 func (e *excludedError) Error() string     { return "excluded by go.mod" }
 func (e *excludedError) Is(err error) bool { return err == ErrDisallowed }
 
-// checkRetractions returns an error if module m has been retracted by
+// CheckRetractions returns an error if module m has been retracted by
 // its author.
-func checkRetractions(ctx context.Context, m module.Version) error {
+func CheckRetractions(ctx context.Context, m module.Version) error {
 	if m.Version == "" {
 		// Main module, standard library, or file replacement module.
 		// Cannot be retracted.
@@ -165,28 +165,28 @@ func checkRetractions(ctx context.Context, m module.Version) error {
 		}
 	}
 	if isRetracted {
-		return module.VersionError(m, &retractedError{rationale: rationale})
+		return module.VersionError(m, &ModuleRetractedError{Rationale: rationale})
 	}
 	return nil
 }
 
 var retractCache par.Cache
 
-type retractedError struct {
+type ModuleRetractedError struct {
-	rationale []string
+	Rationale []string
 }
 
-func (e *retractedError) Error() string {
+func (e *ModuleRetractedError) Error() string {
 	msg := "retracted by module author"
-	if len(e.rationale) > 0 {
+	if len(e.Rationale) > 0 {
 		// This is meant to be a short error printed on a terminal, so just
 		// print the first rationale.
-		msg += ": " + ShortRetractionRationale(e.rationale[0])
+		msg += ": " + ShortRetractionRationale(e.Rationale[0])
 	}
 	return msg
 }
 
-func (e *retractedError) Is(err error) bool {
+func (e *ModuleRetractedError) Is(err error) bool {
 	return err == ErrDisallowed
 }
 

src/cmd/go/testdata/mod/example.com_retract_ambiguous_nested_v1.9.0-bad.txt

@@ -0,0 +1,10 @@
+-- .mod --
+module example.com/retract/ambiguous/nested
+
+go 1.16
+
+retract v1.9.0-bad // nested modules are bad
+-- .info --
+{"Version":"v1.9.0-bad"}
+-- nested.go --
+package nested

src/cmd/go/testdata/mod/example.com_retract_ambiguous_other_v1.0.0.txt

@@ -0,0 +1,12 @@
+-- .mod --
+module example.com/retract/ambiguous/other
+
+go 1.16
+
+require example.com/retract/ambiguous v1.0.0
+-- .info --
+{"Version":"v1.0.0"}
+-- other.go --
+package other
+
+import _ "example.com/retract/ambiguous/nested"

src/cmd/go/testdata/mod/example.com_retract_ambiguous_v1.0.0.txt

@@ -0,0 +1,9 @@
+-- .mod --
+module example.com/retract/ambiguous
+
+go 1.16
+-- .info --
+{"Version":"v1.0.0"}
+-- nested/nested.go --
+package nested
+

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

@@ -10,7 +10,7 @@ stdout '^example.com/retract/self/prev v1.1.0$'
 cp go.mod.orig go.mod
 go mod edit -require example.com/retract/self/prev@v1.9.0
 go get -d example.com/retract/self/prev
-stderr '^go: warning: example.com/retract/self/prev@v1.9.0 is retracted: self$'
+stderr '^go: warning: example.com/retract/self/prev@v1.9.0: retracted by module author: self$'
 go list -m example.com/retract/self/prev
 stdout '^example.com/retract/self/prev v1.9.0$'
 
@@ -25,7 +25,7 @@ stdout '^example.com/retract/self/prev v1.1.0$'
 # version is retracted.
 cp go.mod.orig go.mod
 go get -d example.com/retract@v1.0.0-bad
-stderr '^go: warning: example.com/retract@v1.0.0-bad is retracted: bad$'
+stderr '^go: warning: example.com/retract@v1.0.0-bad: retracted by module author: bad$'
 go list -m example.com/retract
 stdout '^example.com/retract v1.0.0-bad$'
 
@@ -33,17 +33,26 @@ stdout '^example.com/retract v1.0.0-bad$'
 # version is available.
 cp go.mod.orig go.mod
 go mod edit -require example.com/retract/self/prev@v1.9.0
-go get -d -u .
+go get -d -u ./use
-stderr '^go: warning: example.com/retract/self/prev@v1.9.0 is retracted: self$'
+stderr '^go: warning: example.com/retract/self/prev@v1.9.0: retracted by module author: self$'
 go list -m example.com/retract/self/prev
 stdout '^example.com/retract/self/prev v1.9.0$'
 
+# 'go get' should warn if a module needed to build named packages is retracted.
+# 'go get' should not warn about unrelated modules.
+go get -d ./empty
+! stderr retracted
+go get -d ./use
+stderr '^go: warning: example.com/retract/self/prev@v1.9.0: retracted by module author: self$'
+
 -- go.mod.orig --
 module example.com/use
 
 go 1.15
 
--- use.go --
+-- use/use.go --
 package use
 
 import _ "example.com/retract/self/prev"
+-- empty/empty.go --
+package empty

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

@@ -0,0 +1,10 @@
+! go get -d example.com/retract/ambiguous/other
+stderr 'ambiguous import: found package example.com/retract/ambiguous/nested in multiple modules:'
+stderr '^go: warning: example.com/retract/ambiguous/nested@v1.9.0-bad: retracted by module author: nested modules are bad$'
+
+-- go.mod --
+module example.com/use
+
+go 1.16
+
+require example.com/retract/ambiguous/nested v1.9.0-bad

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

@@ -1,6 +1,6 @@
 # When there is no rationale, 'go get' should print a hard-coded message.
 go get -d example.com/retract/rationale@v1.0.0-empty
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-empty is retracted: retracted by module author$'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-empty: retracted by module author$'
 
 # 'go list' should print the same hard-coded message.
 go list -m -retracted -f '{{.Retracted}}' example.com/retract/rationale
@@ -9,7 +9,7 @@ stdout '^\[retracted by module author\]$'
 
 # When there is a multi-line message, 'go get' should print the first line.
 go get -d example.com/retract/rationale@v1.0.0-multiline1
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-multiline1 is retracted: short description$'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-multiline1: retracted by module author: short description$'
 ! stderr 'detail'
 
 # 'go list' should show the full message.
@@ -19,7 +19,7 @@ cmp stdout multiline
 # 'go get' output should be the same whether the retraction appears at top-level
 # or in a block.
 go get -d example.com/retract/rationale@v1.0.0-multiline2
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-multiline2 is retracted: short description$'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-multiline2: retracted by module author: short description$'
 ! stderr 'detail'
 
 # Same for 'go list'.
@@ -29,7 +29,7 @@ cmp stdout multiline
 
 # 'go get' should omit long messages.
 go get -d example.com/retract/rationale@v1.0.0-long
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-long is retracted: \(rationale omitted: too long\)'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-long: retracted by module author: \(rationale omitted: too long\)'
 
 # 'go list' should show the full message.
 go list -m -retracted -f '{{.Retracted}}' example.com/retract/rationale
@@ -38,7 +38,7 @@ stdout '^\[lo{500}ng\]$'
 
 # 'go get' should omit messages with unprintable characters.
 go get -d example.com/retract/rationale@v1.0.0-unprintable
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-unprintable is retracted: \(rationale omitted: contains non-printable characters\)'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-unprintable: retracted by module author: \(rationale omitted: contains non-printable characters\)'
 
 # 'go list' should show the full message.
 go list -m -retracted -f '{{.Retracted}}' example.com/retract/rationale
@@ -62,9 +62,9 @@ stdout '^single version,degenerate range,$'
 
 # 'go get' will only report the first retraction to avoid being too verbose.
 go get -d example.com/retract/rationale@v1.0.0-order
-stderr '^go: warning: example.com/retract/rationale@v1.0.0-order is retracted: degenerate range$'
+stderr '^go: warning: example.com/retract/rationale@v1.0.0-order: retracted by module author: degenerate range$'
 go get -d example.com/retract/rationale@v1.0.1-order
-stderr '^go: warning: example.com/retract/rationale@v1.0.1-order is retracted: single version$'
+stderr '^go: warning: example.com/retract/rationale@v1.0.1-order: retracted by module author: single version$'
 
 -- go.mod --
 module m

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

@@ -10,7 +10,7 @@ go list -m -u -f '{{with .Retracted}}retracted{{end}}' example.com/retract/renam
 
 # 'go get' should warn about the retracted version.
 go get -d
-stderr '^go: warning: example.com/retract/rename@v1.0.0-bad is retracted: bad$'
+stderr '^go: warning: example.com/retract/rename@v1.0.0-bad: retracted by module author: bad$'
 
 # We can't upgrade, since this latest version has a different module path.
 ! go get -d example.com/retract/rename