encoding/protobuf: cope with major version suffixes in module paths

Currently the protobuf logic for determining if an import is
inside the main module does not work if the module has
a major version suffix. This change makes that work OK.

It's not perfect, because we do not consider the major
version that might be present in the Go import path, but
it's certainly better than before.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I36fbc476ecdaff1fce01dd2e5095c77f455bbacf
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194791
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

encoding/protobuf/protobuf.go

@@ -22,14 +22,14 @@
 // # Package Paths
 //
 // If a .proto file contains a go_package directive, it will be used as the
-// destination package fo the generated .cue files. A common use case is to
+// destination package for the generated .cue files. A common use case is to
 // generate the CUE in the same directory as the .proto definition. If a
 // destination package is not within the current CUE module, it will be written
 // relative to the pkg directory.
 //
 // If a .proto file does not specify go_package, it will convert a proto package
 // "google.parent.sub" to the import path "googleapis.com/google/parent/sub".
-// It is safe to mix package with and without a go_package within the same
+// It is safe to mix packages with and without a go_package within the same
 // project.
 //
 // # Type Mappings
@@ -99,6 +99,7 @@ import (
 	"cuelang.org/go/cue/parser"
 	"cuelang.org/go/cue/token"
 	"cuelang.org/go/internal"
+	"cuelang.org/go/mod/module"
 
 	// Generated protobuf CUE may use builtins. Ensure that these can always be
 	// found, even if the user does not use cue/load or another package that
@@ -181,13 +182,27 @@ type result struct {
 // it will be observable by the Err method fo the Extractor. It is safe,
 // however, to only check errors after building the output.
 func NewExtractor(c *Config) *Extractor {
+	var modulePath string
+	// We don't want to consider the module's major version as
+	// part of the path when checking to see a protobuf package
+	// declares itself as part of that module.
+	// TODO(rogpeppe) the Go package path might itself include a major
+	// version, so we should probably consider that too.
+	if c.Module != "" {
+		var ok bool
+		modulePath, _, ok = module.SplitPathVersion(c.Module)
+		if !ok {
+			modulePath = c.Module
+
+		}
+	}
 	cwd, _ := os.Getwd()
 	b := &Extractor{
 		root:      c.Root,
 		cwd:       cwd,
 		paths:     c.Paths,
 		pkgName:   c.PkgName,
-		module:    c.Module,
+		module:    modulePath,
 		enumMode:  c.EnumMode,
 		fileCache: map[string]result{},
 		imports:   map[string]*build.Instance{},

encoding/protobuf/protobuf_test.go

@@ -78,7 +78,7 @@ func TestBuild(t *testing.T) {
 	root := filepath.Join(cwd, "testdata/istio.io/api")
 	c := &Config{
 		Root:   root,
-		Module: "istio.io/api",
+		Module: "istio.io/api@v0",
 		Paths: []string{
 			root,
 			filepath.Join(cwd, "testdata"),