cmd/internal/objabi: add inverse of PathToPrefix

Add PrefixToPath, which can be used to convert a package path in a
symbol name back to the original package path.

For #61577.

Change-Id: Ifbe8c852a7f41ff9b81ad48b92a26a0e1b046777
Reviewed-on: https://go-review.googlesource.com/c/go/+/529557
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

1 files changed, 36 insertions, 7 deletions

diff --git a/src/cmd/internal/objabi/path_test.go b/src/cmd/internal/objabi/path_test.go
index 78b94a3266..934db3dfa0 100644
--- a/src/cmd/internal/objabi/path_test.go
+++ b/src/cmd/internal/objabi/path_test.go
@@ -11,11 +11,11 @@ import (
 	"testing"
 )
 
-func TestPathToPrefix(t *testing.T) {
-	tests := []struct {
-		Path     string
-		Expected string
-	}{{"foo/bar/v1", "foo/bar/v1"},
+var escapeTests = []struct {
+		Path    string
+		Escaped string
+	}{
+		{"foo/bar/v1", "foo/bar/v1"},
 		{"foo/bar/v.1", "foo/bar/v%2e1"},
 		{"f.o.o/b.a.r/v1", "f.o.o/b.a.r/v1"},
 		{"f.o.o/b.a.r/v.1", "f.o.o/b.a.r/v%2e1"},
@@ -30,9 +30,38 @@ func TestPathToPrefix(t *testing.T) {
 		{"%foo%bar", "%25foo%25bar"},
 		{"\x01\x00\x7F☺", "%01%00%7f%e2%98%ba"},
 	}
+
+func TestPathToPrefix(t *testing.T) {
+	for _, tc := range escapeTests {
+		if got := PathToPrefix(tc.Path); got != tc.Escaped {
+			t.Errorf("expected PathToPrefix(%s) = %s, got %s", tc.Path, tc.Escaped, got)
+		}
+	}
+}
+
+func TestPrefixToPath(t *testing.T) {
+	for _, tc := range escapeTests {
+		got, err := PrefixToPath(tc.Escaped)
+		if err != nil {
+			t.Errorf("expected PrefixToPath(%s) err = nil, got %v", tc.Escaped, err)
+		}
+		if got != tc.Path {
+			t.Errorf("expected PrefixToPath(%s) = %s, got %s", tc.Escaped, tc.Path, got)
+		}
+	}
+}
+
+func TestPrefixToPathError(t *testing.T) {
+	tests := []string{
+		"foo%",
+		"foo%1",
+		"foo%%12",
+		"foo%1g",
+	}
 	for _, tc := range tests {
-		if got := PathToPrefix(tc.Path); got != tc.Expected {
-			t.Errorf("expected PathToPrefix(%s) = %s, got %s", tc.Path, tc.Expected, got)
+		_, err := PrefixToPath(tc)
+		if err == nil {
+			t.Errorf("expected PrefixToPath(%s) err != nil, got nil", tc)
 		}
 	}
 }