fix: parse showcase resource patterns (#3271)

Related to #3258 

Parsing showcase protos does not work. This is blocking sidekick updates
for `google-coud-rust`. Add a temporary workaround.

Author: dbolduc

internal/sidekick/parser/httprule/http_rule_parser.go

@@ -93,6 +93,11 @@ func ParseSegments(pathTemplate string) (*api.PathTemplate, error) {
 func ParseResourcePattern(pathTemplate string) (*api.PathTemplate, error) {
 	// TODO(https://github.com/googleapis/librarian/issues/3258): ParseResourcePattern
 	// should support parsing generic resources more robustly than just checking for a literal `*`.
+	if strings.Contains(pathTemplate, "}.{") ||
+		strings.Contains(pathTemplate, "}~{") {
+		// TODO(https://github.com/googleapis/librarian/issues/3258): support non-standard separators in resource names... somehow.
+		return api.NewPathTemplate(), nil
+	}
 	if pathTemplate == api.SingleSegmentWildcard {
 		return api.NewPathTemplate(), nil
 	}

internal/sidekick/parser/httprule/http_rule_parser_test.go

@@ -190,3 +190,31 @@ func TestParseResourcePattern(t *testing.T) {
 		})
 	}
 }
+
+func TestParseResourcePatternWithNonStandardSeparators(t *testing.T) {
+	// TODO(https://github.com/googleapis/librarian/issues/3258): at this
+	// moment, we don't care what the exact representation is for this
+	// input. We just care that parsing does not error.
+	testCases := []struct {
+		name    string
+		pattern string
+	}{
+		{
+			name:    "tilde separator",
+			pattern: "users/{user}/profile/blurbs/legacy/{legacy_user}~{blurb}",
+		},
+		{
+			name:    "dot separator",
+			pattern: "rooms/{room}/blurbs/legacy/{legacy_room}.{blurb}",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := ParseResourcePattern(tc.pattern)
+			if err != nil {
+				t.Fatalf("ParseResourcePattern(%q) failed; want no error, got %v", tc.pattern, err)
+			}
+		})
+	}
+}