cmd/go: support module deprecation

A module is deprecated if its author adds a comment containing a
paragraph starting with "Deprecated:" to its go.mod file. The comment
must appear immediately before the "module" directive or as a suffix
on the same line. The deprecation message runs from just after
"Deprecated:" to the end of the paragraph. This is implemented in
CL 301089.

'go list -m -u' loads deprecation messages from the latest version of
each module, not considering retractions (i.e., deprecations and
retractions are loaded from the same version). By default, deprecated
modules are printed with a "(deprecated)" suffix. The full deprecation
message is available in the -f and -json output.

'go get' prints deprecation warnings for modules named on the command
line. It also prints warnings for modules needed to build packages
named on the command line if those modules are direct dependencies of
the main module.

For #40357

Change-Id: Id81fb2b24710681b025becd6cd74f746f4378e78
Reviewed-on: https://go-review.googlesource.com/c/go/+/306334
Trust: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/src/cmd/go/internal/modcmd/edit.go b/src/cmd/go/internal/modcmd/edit.go
index 1df104eb1d..e1ec088f55 100644
--- a/src/cmd/go/internal/modcmd/edit.go
+++ b/src/cmd/go/internal/modcmd/edit.go
@@ -86,7 +86,7 @@ writing it back to go.mod. The JSON output corresponds to these Go types:
 
 	type Module struct {
 		Path string
-		Version string
+		Deprecated string
 	}
 
 	type GoMod struct {
@@ -450,7 +450,7 @@ func flagDropRetract(arg string) {
 
 // fileJSON is the -json output data structure.
 type fileJSON struct {
-	Module  module.Version
+	Module  editModuleJSON
 	Go      string `json:",omitempty"`
 	Require []requireJSON
 	Exclude []module.Version
@@ -458,6 +458,11 @@ type fileJSON struct {
 	Retract []retractJSON
 }
 
+type editModuleJSON struct {
+	Path       string
+	Deprecated string `json:",omitempty"`
+}
+
 type requireJSON struct {
 	Path     string
 	Version  string `json:",omitempty"`
@@ -479,7 +484,10 @@ type retractJSON struct {
 func editPrintJSON(modFile *modfile.File) {
 	var f fileJSON
 	if modFile.Module != nil {
-		f.Module = modFile.Module.Mod
+		f.Module = editModuleJSON{
+			Path:       modFile.Module.Mod.Path,
+			Deprecated: modFile.Module.Deprecated,
+		}
 	}
 	if modFile.Go != nil {
 		f.Go = modFile.Go.Version