Reject an empty option name in getMatchingOptions

src/main/java/org/apache/commons/cli/Options.java

@@ -212,13 +212,17 @@ public Options addRequiredOption(final String opt, final String longOpt, final b
     /**
      * Gets the options with a long name starting with the name specified.
      *
-     * @param opt The partial name of the option.
-     * @return The options matching the partial name specified, or an empty list if none matches.
+     * @param opt The partial name of the option, or {@code null}.
+     * @return The options matching the partial name specified, or an empty list if none matches or the name is null or empty.
      * @since 1.3
      */
     public List<String> getMatchingOptions(final String opt) {
         final String clean = Util.stripLeadingHyphens(opt);
         final List<String> matchingOpts = new ArrayList<>();
+        // a null or empty name is not a partial name; empty would match every long option
+        if (Util.isEmpty(clean)) {
+            return matchingOpts;
+        }
         // for a perfect match return the single option only
         if (longOpts.containsKey(clean)) {
             return Collections.singletonList(clean);

src/test/java/org/apache/commons/cli/OptionsTest.java

@@ -182,6 +182,20 @@ void testGetMatchingOpts() {
         assertToStrings(options.getOption("verbose"));
     }
 
+    @Test
+    void testGetMatchingOptsEmptyName() throws Exception {
+        final Options options = new Options();
+        options.addOption(Option.builder("c").longOpt("config-file").hasArg().get());
+        assertTrue(options.getMatchingOptions(null).isEmpty());
+        assertTrue(options.getMatchingOptions("").isEmpty());
+        assertTrue(options.getMatchingOptions("-").isEmpty());
+        assertTrue(options.getMatchingOptions("--").isEmpty());
+        // "--=value" names no option, so it must not bind a value to config-file
+        for (final CommandLineParser parser : new CommandLineParser[] { new DefaultParser(), new PosixParser() }) {
+            assertThrows(UnrecognizedOptionException.class, () -> parser.parse(options, new String[] { "--=/etc/shadow" }));
+        }
+    }
+
     @Test
     void testGetOptionsGroups() {
         final Options options = new Options();