[ruby/prism] Exclude encodings that are dynamic

https://github.com/ruby/prism/commit/6749146c0e

prism/encoding.c

@@ -5022,10 +5022,6 @@ pm_encoding_find(const uint8_t *start, const uint8_t *end) {
                 ENCODING2("EUC-CN", "eucCN", PM_ENCODING_GB2312);
                 ENCODING2("EUC-TW", "eucTW", PM_ENCODING_EUC_TW);
                 ENCODING1("Emacs-Mule", PM_ENCODING_EMACS_MULE);
-                ENCODING1("external", PM_ENCODING_UTF_8);
-                break;
-            case 'F': case 'f':
-                ENCODING1("filesystem", PM_ENCODING_UTF_8);
                 break;
             case 'G': case 'g':
                 ENCODING1("GBK", PM_ENCODING_GBK);
@@ -5071,9 +5067,6 @@ pm_encoding_find(const uint8_t *start, const uint8_t *end) {
                 ENCODING1("KOI8-R", PM_ENCODING_KOI8_R);
                 ENCODING1("KOI8-U", PM_ENCODING_KOI8_U);
                 break;
-            case 'L': case 'l':
-                ENCODING1("locale", PM_ENCODING_UTF_8);
-                break;
             case 'M': case 'm':
                 ENCODING1("macCentEuro", PM_ENCODING_MAC_CENT_EURO);
                 ENCODING1("macCroatian", PM_ENCODING_MAC_CROATIAN);

test/prism/encoding_test.rb

@@ -137,9 +137,7 @@ module Prism
     # These test that we're correctly parsing codepoints for each alias of each
     # encoding that prism supports.
     encodings.each do |encoding, range|
-      encoding.names.each do |name|
-        next if name == "locale"
-
+      (encoding.names - %w[external internal filesystem locale]).each do |name|
         define_method(:"test_encoding_#{name}") do
           assert_encoding(encoding, name, range)
         end