cmd/go/internal/modcmd: loosen path validation in "go mod edit"

Replaced modules require only valid import paths, not full
module paths that can be fetched with 'go get'.

The 'go' command does not in general reject manually-edited go.mod
files with these paths, so 'go mod edit' should not reject them
either.

Fixes #30513

Change-Id: I4f1a5c65937f91d41478f8d218c8018e0c70f320
Reviewed-on: https://go-review.googlesource.com/c/go/+/210343
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/modcmd/edit.go

@@ -164,7 +164,7 @@ func runEdit(cmd *base.Command, args []string) {
 	}
 
 	if *editModule != "" {
-		if err := module.CheckPath(*editModule); err != nil {
+		if err := module.CheckImportPath(*editModule); err != nil {
 			base.Fatalf("go mod: invalid -module: %v", err)
 		}
 	}
@@ -242,7 +242,7 @@ func parsePathVersion(flag, arg string) (path, version string) {
 		base.Fatalf("go mod: -%s=%s: need path@version", flag, arg)
 	}
 	path, version = strings.TrimSpace(arg[:i]), strings.TrimSpace(arg[i+1:])
-	if err := module.CheckPath(path); err != nil {
+	if err := module.CheckImportPath(path); err != nil {
 		base.Fatalf("go mod: -%s=%s: invalid path: %v", flag, arg, err)
 	}
 
@@ -264,7 +264,7 @@ func parsePath(flag, arg string) (path string) {
 		base.Fatalf("go mod: -%s=%s: need just path, not path@version", flag, arg)
 	}
 	path = arg
-	if err := module.CheckPath(path); err != nil {
+	if err := module.CheckImportPath(path); err != nil {
 		base.Fatalf("go mod: -%s=%s: invalid path: %v", flag, arg, err)
 	}
 	return path
@@ -278,7 +278,7 @@ func parsePathVersionOptional(adj, arg string, allowDirPath bool) (path, version
 	} else {
 		path, version = strings.TrimSpace(arg[:i]), strings.TrimSpace(arg[i+1:])
 	}
-	if err := module.CheckPath(path); err != nil {
+	if err := module.CheckImportPath(path); err != nil {
 		if !allowDirPath || !modfile.IsDirectoryPath(path) {
 			return path, version, fmt.Errorf("invalid %s path: %v", adj, err)
 		}

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

@@ -52,6 +52,12 @@ go mod init a.a/b/c
 go mod edit -module x.x/y/z
 cmpenv go.mod go.mod.edit
 
+# golang.org/issue/30513: don't require go-gettable module paths.
+cd $WORK/local
+go mod init foo
+go mod edit -module local-only -require=other-local@v1.0.0 -replace other-local@v1.0.0=./other
+cmpenv go.mod go.mod.edit
+
 -- x.go --
 package x
 
@@ -159,6 +165,14 @@ exclude x.1 v1.2.0
 replace x.1 => y.1/v2 v2.3.6
 
 require x.3 v1.99.0
+-- $WORK/local/go.mod.edit --
+module local-only
+
+go $goversion
+
+require other-local v1.0.0
+
+replace other-local v1.0.0 => ./other
 -- $WORK/go.mod.badfmt --
 module     x.x/y/z