cmd/go: refactor -mod flag parsing

Keep track of whether the -mod flag was set explicitly. When
-mod=readonly is the default, we'll want to adjust our error messages
if it's set explicitly.

Also, register the -mod, -modcacherw, and -modfile flags in functions
in internal/base instead of internal/work. 'go mod' commands that
don't load packages shouldn't depend on internal/work.

For #40728

Change-Id: I272aea9e19908ba37e151baac4ea8630e90f241f
Reviewed-on: https://go-review.googlesource.com/c/go/+/253744
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 3 insertions, 11 deletions

diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index d020aa6e9f..e99982ed36 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -240,13 +240,12 @@ const (
 // AddBuildFlags adds the flags common to the build, clean, get,
 // install, list, run, and test commands.
 func AddBuildFlags(cmd *base.Command, mask BuildFlagMask) {
+	base.AddBuildFlagsNX(&cmd.Flag)
 	cmd.Flag.BoolVar(&cfg.BuildA, "a", false, "")
-	cmd.Flag.BoolVar(&cfg.BuildN, "n", false, "")
 	cmd.Flag.IntVar(&cfg.BuildP, "p", cfg.BuildP, "")
 	if mask&OmitVFlag == 0 {
 		cmd.Flag.BoolVar(&cfg.BuildV, "v", false, "")
 	}
-	cmd.Flag.BoolVar(&cfg.BuildX, "x", false, "")
 
 	cmd.Flag.Var(&load.BuildAsmflags, "asmflags", "")
 	cmd.Flag.Var(buildCompiler{}, "compiler", "")
@@ -254,10 +253,10 @@ func AddBuildFlags(cmd *base.Command, mask BuildFlagMask) {
 	cmd.Flag.Var(&load.BuildGcflags, "gcflags", "")
 	cmd.Flag.Var(&load.BuildGccgoflags, "gccgoflags", "")
 	if mask&OmitModFlag == 0 {
-		cmd.Flag.StringVar(&cfg.BuildMod, "mod", "", "")
+		base.AddModFlag(&cmd.Flag)
 	}
 	if mask&OmitModCommonFlags == 0 {
-		AddModCommonFlags(cmd)
+		base.AddModCommonFlags(&cmd.Flag)
 	}
 	cmd.Flag.StringVar(&cfg.BuildContext.InstallSuffix, "installsuffix", "", "")
 	cmd.Flag.Var(&load.BuildLdflags, "ldflags", "")
@@ -275,13 +274,6 @@ func AddBuildFlags(cmd *base.Command, mask BuildFlagMask) {
 	cmd.Flag.StringVar(&cfg.DebugTrace, "debug-trace", "", "")
 }
 
-// AddModCommonFlags adds the module-related flags common to build commands
-// and 'go mod' subcommands.
-func AddModCommonFlags(cmd *base.Command) {
-	cmd.Flag.BoolVar(&cfg.ModCacheRW, "modcacherw", false, "")
-	cmd.Flag.StringVar(&cfg.ModFile, "modfile", "", "")
-}
-
 // tagsFlag is the implementation of the -tags flag.
 type tagsFlag []string