add test case for ImportMap support (#186)

We also update the "original types importer" to support ImportMap.

The test now gets further along, no longer getting stuck on "path not
found in listed packages". Instead, we get stuck on:

	error parsing importcfg: <...>/importcfg:2: unknown directive "importmap"

This bug has been filed at https://github.com/Binject/debug/issues/17.
Until it's fixed, we can't really proceed on #146, so the net import in
the test file (which triggers this case) is commented out for now.

Updates #146.

main.go

@@ -90,16 +90,18 @@ var (
 	b64         = base64.NewEncoding(nameCharset)
 	printConfig = printer.Config{Mode: printer.RawFormat}
 
-	// origTypesConfig configures a go/types typechecker which uses the
-	// original versions of packages, without any obfuscation. This is
-	// helpful to make decisions on how to obfuscate our input code.
-	origTypesConfig = types.Config{Importer: importer.ForCompiler(fset, "gc", func(path string) (io.ReadCloser, error) {
-		pkg, err := listPackage(path)
-		if err != nil {
-			return nil, err
-		}
-		return os.Open(pkg.Export)
-	})}
+	// origImporter configures a go/types importer which uses the original
+	// versions of packages, without any obfuscation. This is helpful to
+	// make decisions on how to obfuscate our input code.
+	origImporter = func(fromPkg string) types.Importer {
+		return importer.ForCompiler(fset, "gc", func(path string) (io.ReadCloser, error) {
+			pkg, err := listPackage(fromPkg, path)
+			if err != nil {
+				return nil, err
+			}
+			return os.Open(pkg.Export)
+		})
+	}
 
 	buildInfo = struct {
 		actionID  []byte // from -buildid
@@ -183,12 +185,13 @@ type listedPackage struct {
 	ImportPath string
 	Export     string
 	Deps       []string
+	ImportMap  map[string]string
 
 	// TODO(mvdan): reuse this field once TOOLEXEC_IMPORTPATH is used
 	private bool
 }
 
-func listPackage(path string) (*listedPackage, error) {
+func listPackage(fromPath, path string) (*listedPackage, error) {
 	if listedPackages == nil {
 		f, err := os.Open(envGarbleListPkgs)
 		if err != nil {
@@ -201,6 +204,11 @@ func listPackage(path string) (*listedPackage, error) {
 	}
 	pkg, ok := listedPackages[path]
 	if !ok {
+		if fromPkg, ok := listedPackages[fromPath]; ok {
+			if path2 := fromPkg.ImportMap[path]; path2 != "" {
+				return listPackage(fromPath, path2)
+			}
+		}
 		return nil, fmt.Errorf("path not found in listed packages: %s", path)
 	}
 	return pkg, nil
@@ -636,6 +644,9 @@ func transformCompile(args []string) ([]string, error) {
 		},
 	}
 
+	origTypesConfig := types.Config{
+		Importer: origImporter(pkgPath),
+	}
 	tf.pkg, err = origTypesConfig.Check(pkgPath, fset, files, tf.info)
 	if err != nil {
 		return nil, fmt.Errorf("typecheck error: %v", err)

testdata/scripts/goprivate.txt

@@ -8,6 +8,9 @@ stderr '^public package "test/main/importer" can''t depend on obfuscated package
 
 [short] stop
 
+# Try garbling all of std.
+# This used to fail since the "net" import causes 'go list -json' to output
+# ImportMap, since "net" imports packages vendored in std.
 env GOPRIVATE='*'
 garble build -o=out ./standalone
 
@@ -18,6 +21,9 @@ go 1.15
 -- standalone/main.go --
 package main
 
+// Blocked until https://github.com/Binject/debug/issues/17 is fixed.
+// import _ "net"
+
 func main() {}
 -- importer/importer.go --
 package importer