cmd/go: add -retracted flag to 'go list'

The -retracted flag causes 'go list' to load information about
retracted module module versions.

When -retracted is used with -f or -json, the Retracted field is set
to a string containing the reason for the retraction on retracted
module versions. The string is based on comments on the retract
directive. This field is also populated when the -u flag is used.

When -retracted is used with -versions, retracted versions are shown.
Normally, they are omitted.

For #24031

Change-Id: Ic13d516eddffb1b8404e21034f78cecc9896d1b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/228382
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 86 insertions, 14 deletions

diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index e68c39f392..6d81c1cad1 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
 	"io"
 	"os"
 	"sort"
@@ -215,6 +216,7 @@ applied to a Go struct, but now a Module struct:
         Dir       string       // directory holding files for this module, if any
         GoMod     string       // path to go.mod file used when loading this module, if any
         GoVersion string       // go version used in module
+        Retracted string       // retraction information, if any (with -retracted or -u)
         Error     *ModuleError // error loading module
     }
 
@@ -246,14 +248,16 @@ the replaced source code.)
 The -u flag adds information about available upgrades.
 When the latest version of a given module is newer than
 the current one, list -u sets the Module's Update field
-to information about the newer module.
+to information about the newer module. list -u will also set
+the module's Retracted field if the current version is retracted.
 The Module's String method indicates an available upgrade by
 formatting the newer version in brackets after the current version.
+If a version is retracted, the string "(retracted)" will follow it.
 For example, 'go list -m -u all' might print:
 
     my/main/module
     golang.org/x/text v0.3.0 [v0.4.0] => /tmp/text
-    rsc.io/pdf v0.1.1 [v0.1.2]
+    rsc.io/pdf v0.1.1 (retracted) [v0.1.2]
 
 (For tools, 'go list -m -u -json all' may be more convenient to parse.)
 
@@ -263,6 +267,14 @@ to semantic versioning, earliest to latest. The flag also changes
 the default output format to display the module path followed by the
 space-separated version list.
 
+The -retracted flag causes list to report information about retracted
+module versions. When -retracted is used with -f or -json, the Retracted
+field will be set to a string explaining why the version was retracted.
+The string is taken from comments on the retract directive in the
+module's go.mod file. When -retracted is used with -versions, retracted
+versions are listed together with unretracted versions. The -retracted
+flag may be used with or without -m.
+
 The arguments to list -m are interpreted as a list of modules, not packages.
 The main module is the module containing the current directory.
 The active modules are the main module and its dependencies.
@@ -296,17 +308,18 @@ func init() {
 }
 
 var (
-	listCompiled = CmdList.Flag.Bool("compiled", false, "")
-	listDeps     = CmdList.Flag.Bool("deps", false, "")
-	listE        = CmdList.Flag.Bool("e", false, "")
-	listExport   = CmdList.Flag.Bool("export", false, "")
-	listFmt      = CmdList.Flag.String("f", "", "")
-	listFind     = CmdList.Flag.Bool("find", false, "")
-	listJson     = CmdList.Flag.Bool("json", false, "")
-	listM        = CmdList.Flag.Bool("m", false, "")
-	listU        = CmdList.Flag.Bool("u", false, "")
-	listTest     = CmdList.Flag.Bool("test", false, "")
-	listVersions = CmdList.Flag.Bool("versions", false, "")
+	listCompiled  = CmdList.Flag.Bool("compiled", false, "")
+	listDeps      = CmdList.Flag.Bool("deps", false, "")
+	listE         = CmdList.Flag.Bool("e", false, "")
+	listExport    = CmdList.Flag.Bool("export", false, "")
+	listFmt       = CmdList.Flag.String("f", "", "")
+	listFind      = CmdList.Flag.Bool("find", false, "")
+	listJson      = CmdList.Flag.Bool("json", false, "")
+	listM         = CmdList.Flag.Bool("m", false, "")
+	listRetracted = CmdList.Flag.Bool("retracted", false, "")
+	listTest      = CmdList.Flag.Bool("test", false, "")
+	listU         = CmdList.Flag.Bool("u", false, "")
+	listVersions  = CmdList.Flag.Bool("versions", false, "")
 )
 
 var nl = []byte{'\n'}
@@ -367,6 +380,16 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 		}
 	}
 
+	modload.Init()
+	if *listRetracted {
+		if cfg.BuildMod == "vendor" {
+			base.Fatalf("go list -retracted cannot be used when vendoring is enabled")
+		}
+		if !modload.Enabled() {
+			base.Fatalf("go list -retracted can only be used in module-aware mode")
+		}
+	}
+
 	if *listM {
 		// Module mode.
 		if *listCompiled {
@@ -416,7 +439,7 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 
 		modload.LoadBuildList(ctx)
 
-		mods := modload.ListModules(ctx, args, *listU, *listVersions)
+		mods := modload.ListModules(ctx, args, *listU, *listVersions, *listRetracted)
 		if !*listE {
 			for _, m := range mods {
 				if m.Error != nil {
@@ -607,6 +630,55 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 		}
 	}
 
+	// TODO(golang.org/issue/40676): This mechanism could be extended to support
+	// -u without -m.
+	if *listRetracted {
+		// Load retractions for modules that provide packages that will be printed.
+		// TODO(golang.org/issue/40775): Packages from the same module refer to
+		// distinct ModulePublic instance. It would be nice if they could all point
+		// to the same instance. This would require additional global state in
+		// modload.loaded, so that should be refactored first. For now, we update
+		// all instances.
+		modToArg := make(map[*modinfo.ModulePublic]string)
+		argToMods := make(map[string][]*modinfo.ModulePublic)
+		var args []string
+		addModule := func(mod *modinfo.ModulePublic) {
+			if mod.Version == "" {
+				return
+			}
+			arg := fmt.Sprintf("%s@%s", mod.Path, mod.Version)
+			if argToMods[arg] == nil {
+				args = append(args, arg)
+			}
+			argToMods[arg] = append(argToMods[arg], mod)
+			modToArg[mod] = arg
+		}
+		for _, p := range pkgs {
+			if p.Module == nil {
+				continue
+			}
+			addModule(p.Module)
+			if p.Module.Replace != nil {
+				addModule(p.Module.Replace)
+			}
+		}
+
+		if len(args) > 0 {
+			listU := false
+			listVersions := false
+			rmods := modload.ListModules(ctx, args, listU, listVersions, *listRetracted)
+			for i, arg := range args {
+				rmod := rmods[i]
+				for _, mod := range argToMods[arg] {
+					mod.Retracted = rmod.Retracted
+					if rmod.Error != nil && mod.Error == nil {
+						mod.Error = rmod.Error
+					}
+				}
+			}
+		}
+	}
+
 	// Record non-identity import mappings in p.ImportMap.
 	for _, p := range pkgs {
 		for i, srcPath := range p.Internal.RawImports {