feat(core): flag yielding arguments (#367)

Implements https://github.com/Incendo/cloud/issues/218
Also confirmed to fix https://github.com/Incendo/cloud/issues/321.

Both `StringArgument` and `StringArrayArgument` now have flag-yielding modes. For annotated command method users, this can be activated using ´@FlagYielding`

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Core: Add `DurationArgument` for parsing `java.time.Duration` ([#330](https://github.com/Incendo/cloud/pull/330)) 
 - Core: Add delegating command execution handlers ([#363](https://github.com/Incendo/cloud/pull/363))
 - Core: Add `builder()` getter to `Command.Builder` ([#363](https://github.com/Incendo/cloud/pull/363))
+- Core: Add flag yielding modes to `StringArgument` and `StringArrayArgument` ([#367](https://github.com/Incendo/cloud/pull/367))
 - Annotations: Annotation string processors ([#353](https://github.com/Incendo/cloud/pull/353))
 - Annotations: `@CommandContainer` annotation processing ([#364](https://github.com/Incendo/cloud/pull/364))
 - Annotations: `@CommandMethod` annotation processing for compile-time validation ([#365](https://github.com/Incendo/cloud/pull/365))

cloud-core/src/main/java/cloud/commandframework/annotations/specifier/FlagYielding.java

@@ -0,0 +1,43 @@
+//
+// MIT License
+//
+// Copyright (c) 2021 Alexander Söderberg & Contributors
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+package cloud.commandframework.annotations.specifier;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that the argument should stop parsing when encountering what
+ * could potentially be a flag.
+ * <p>
+ * This only has an effect on greedy arguments that consume all remaining input.
+ *
+ * @since 1.7.0
+ */
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.PARAMETER)
+public @interface FlagYielding {
+
+}

cloud-core/src/main/java/cloud/commandframework/arguments/compound/FlagArgument.java

@@ -57,8 +57,8 @@ import org.checkerframework.checker.nullness.qual.NonNull;
  */
 public final class FlagArgument<C> extends CommandArgument<C, Object> {
 
-    private static final Pattern FLAG_ALIAS_PATTERN = Pattern.compile(" -(?<name>([A-Za-z]+))");
     private static final Pattern FLAG_PRIMARY_PATTERN = Pattern.compile(" --(?<name>([A-Za-z]+))");
+    private static final Pattern FLAG_ALIAS_PATTERN = Pattern.compile(" -(?<name>([A-Za-z]+))");
 
     /**
      * Dummy object that indicates that flags were parsed successfully
@@ -125,13 +125,13 @@ public final class FlagArgument<C> extends CommandArgument<C, Object> {
         /**
          * Parse command input to figure out what flag is currently being
          * typed at the end of the input queue. If no flag value is being
-         * inputed, returns {@link Optional#empty()}.<br>
+         * inputted, returns {@link Optional#empty()}.<br>
          * <br>
          * Will consume all but the last element from the input queue.
          *
          * @param commandContext Command context
          * @param inputQueue The input queue of arguments
-         * @return current flag being typed, or <i>empty()</i> if none is
+         * @return current flag being typed, or {@code empty()} if none is
          */
         public @NonNull Optional<String> parseCurrentFlag(
                 final @NonNull CommandContext<@NonNull C> commandContext,

cloud-core/src/main/java/cloud/commandframework/arguments/parser/StandardParameters.java

@@ -59,6 +59,16 @@ public final class StandardParameters {
      * Indicates that a string argument should be greedy
      */
     public static final ParserParameter<Boolean> GREEDY = create("greedy", TypeToken.get(Boolean.class));
+    /**
+     * Indicates that an argument should stop parsing when encountering a potential flag.
+     *
+     * @since 1.7.0
+     * @see cloud.commandframework.annotations.specifier.FlagYielding
+     */
+    public static final ParserParameter<Boolean> FLAG_YIELDING = create(
+            "flag_yielding",
+            TypeToken.get(Boolean.class)
+    );
     /**
      * Indicates that a string argument should be quoted.
      *

cloud-core/src/main/java/cloud/commandframework/arguments/parser/StandardParserRegistry.java

@@ -23,6 +23,7 @@
 //
 package cloud.commandframework.arguments.parser;
 
+import cloud.commandframework.annotations.specifier.FlagYielding;
 import cloud.commandframework.annotations.specifier.Greedy;
 import cloud.commandframework.annotations.specifier.Liberal;
 import cloud.commandframework.annotations.specifier.Quoted;
@@ -104,6 +105,10 @@ public final class StandardParserRegistry<C> implements ParserRegistry<C> {
                 Liberal.class,
                 (liberal, typeToken) -> ParserParameters.single(StandardParameters.LIBERAL, true)
         );
+        this.<FlagYielding, String>registerAnnotationMapper(
+                FlagYielding.class,
+                (flagYielding, typeToken) -> ParserParameters.single(StandardParameters.FLAG_YIELDING, true)
+        );
 
         /* Register standard types */
         this.registerParserSupplier(TypeToken.get(Byte.class), options ->
@@ -137,10 +142,13 @@ public final class StandardParserRegistry<C> implements ParserRegistry<C> {
                         (double) options.get(StandardParameters.RANGE_MAX, Double.POSITIVE_INFINITY)
                 ));
         this.registerParserSupplier(TypeToken.get(Character.class), options -> new CharArgument.CharacterParser<>());
-        this.registerParserSupplier(TypeToken.get(String[].class), options -> new StringArrayArgument.StringArrayParser<>());
+        this.registerParserSupplier(TypeToken.get(String[].class), options ->
+                new StringArrayArgument.StringArrayParser<>(options.get(StandardParameters.FLAG_YIELDING, false))
+        );
         /* Make this one less awful */
         this.registerParserSupplier(TypeToken.get(String.class), options -> {
             final boolean greedy = options.get(StandardParameters.GREEDY, false);
+            final boolean greedyFlagAware = options.get(StandardParameters.FLAG_YIELDING, false);
             final boolean quoted = options.get(StandardParameters.QUOTED, false);
             if (greedy && quoted) {
                 throw new IllegalArgumentException(
@@ -150,6 +158,8 @@ public final class StandardParserRegistry<C> implements ParserRegistry<C> {
             final StringArgument.StringMode stringMode;
             if (greedy) {
                 stringMode = StringArgument.StringMode.GREEDY;
+            } else if (greedyFlagAware) {
+                stringMode = StringArgument.StringMode.GREEDY_FLAG_YIELDING;
             } else if (quoted) {
                 stringMode = StringArgument.StringMode.QUOTED;
             } else {

cloud-core/src/main/java/cloud/commandframework/arguments/standard/StringArgument.java

@@ -166,6 +166,18 @@ public final class StringArgument<C> extends CommandArgument<C, String> {
         return of(name, StringMode.GREEDY);
     }
 
+    /**
+     * Create a new required command argument with the 'greedy flag yielding' parsing mode
+     *
+     * @param name Argument name
+     * @param <C>  Command sender type
+     * @return Created argument
+     * @since 1.7.0
+     */
+    public static <C> @NonNull CommandArgument<C, String> greedyFlagYielding(final @NonNull String name) {
+        return of(name, StringMode.GREEDY_FLAG_YIELDING);
+    }
+
     /**
      * Create a new required command argument with the 'quoted' parsing mode
      *
@@ -189,8 +201,14 @@ public final class StringArgument<C> extends CommandArgument<C, String> {
 
     public enum StringMode {
         SINGLE,
+        QUOTED,
         GREEDY,
-        QUOTED
+        /**
+         * Greedy string that will consume the input until a flag is present.
+         *
+         * @since 1.7.0
+         */
+        GREEDY_FLAG_YIELDING
     }
 
 
@@ -224,6 +242,17 @@ public final class StringArgument<C> extends CommandArgument<C, String> {
             return this;
         }
 
+        /**
+         * Greedy string that will consume the input until a flag is present.
+         *
+         * @return Builder instance
+         * @since 1.7.0
+         */
+        public @NonNull @This Builder<C> greedyFlagYielding() {
+            this.stringMode = StringMode.GREEDY_FLAG_YIELDING;
+            return this;
+        }
+
         /**
          * Set the string mode to single
          *
@@ -274,8 +303,11 @@ public final class StringArgument<C> extends CommandArgument<C, String> {
     }
 
 
+    @SuppressWarnings("UnnecessaryLambda")
     public static final class StringParser<C> implements ArgumentParser<C, String> {
 
+        private static final Pattern FLAG_PATTERN = Pattern.compile("(-[A-Za-z_\\-0-9])|(--[A-Za-z_\\-0-9]*)");
+
         private final StringMode stringMode;
         private final BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider;
 
@@ -390,6 +422,13 @@ public final class StringArgument<C> extends CommandArgument<C, String> {
                     break;
                 }
 
+                if (this.stringMode == StringMode.GREEDY_FLAG_YIELDING) {
+                    // The pattern requires a leading space.
+                    if (FLAG_PATTERN.matcher(string).matches()) {
+                        break;
+                    }
+                }
+
                 sj.add(string);
                 inputQueue.remove();
             }

cloud-core/src/main/java/cloud/commandframework/arguments/standard/StringArrayArgument.java

@@ -29,9 +29,11 @@ import cloud.commandframework.arguments.parser.ArgumentParseResult;
 import cloud.commandframework.arguments.parser.ArgumentParser;
 import cloud.commandframework.context.CommandContext;
 import io.leangen.geantyref.TypeToken;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Queue;
 import java.util.function.BiFunction;
+import java.util.regex.Pattern;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
 
@@ -48,12 +50,13 @@ public final class StringArrayArgument<C> extends CommandArgument<C, String[]> {
             final boolean required,
             final @NonNull String name,
             final @Nullable BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider,
-            final @NonNull ArgumentDescription defaultDescription
+            final @NonNull ArgumentDescription defaultDescription,
+            final boolean flagYielding
     ) {
         super(
                 required,
                 name,
-                new StringArrayParser<>(),
+                new StringArrayParser<>(flagYielding),
                 "",
                 TypeToken.get(String[].class),
                 suggestionsProvider,
@@ -74,10 +77,35 @@ public final class StringArrayArgument<C> extends CommandArgument<C, String[]> {
             final @NonNull BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider
     ) {
         return new StringArrayArgument<>(
-                true,
+                true /* required */,
                 name,
                 suggestionsProvider,
-                ArgumentDescription.empty()
+                ArgumentDescription.empty(),
+                false /* flagYielding */
+        );
+    }
+
+    /**
+     * Create a new required string array argument
+     *
+     * @param name                Argument name
+     * @param flagYielding        Whether the parser should stop parsing when encountering a potential flag
+     * @param suggestionsProvider Suggestions provider
+     * @param <C>                 Command sender type
+     * @return Created argument
+     * @since 1.7.0
+     */
+    public static <C> @NonNull StringArrayArgument<C> of(
+            final @NonNull String name,
+            final boolean flagYielding,
+            final @NonNull BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider
+    ) {
+        return new StringArrayArgument<>(
+                true /* required */,
+                name,
+                suggestionsProvider,
+                ArgumentDescription.empty(),
+                flagYielding
         );
     }
 
@@ -94,10 +122,35 @@ public final class StringArrayArgument<C> extends CommandArgument<C, String[]> {
             final @NonNull BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider
     ) {
         return new StringArrayArgument<>(
-                false,
+                false /* required */,
                 name,
                 suggestionsProvider,
-                ArgumentDescription.empty()
+                ArgumentDescription.empty(),
+                false /* flagYielding */
+        );
+    }
+
+    /**
+     * Create a new optional string array argument
+     *
+     * @param name                Argument name
+     * @param flagYielding        Whether the parser should stop parsing when encountering a potential flag
+     * @param suggestionsProvider Suggestions provider
+     * @param <C>                 Command sender type
+     * @return Created argument
+     * @since 1.7.0
+     */
+    public static <C> @NonNull StringArrayArgument<C> optional(
+            final @NonNull String name,
+            final boolean flagYielding,
+            final @NonNull BiFunction<CommandContext<C>, String, List<String>> suggestionsProvider
+    ) {
+        return new StringArrayArgument<>(
+                false /* required */,
+                name,
+                suggestionsProvider,
+                ArgumentDescription.empty(),
+                flagYielding
         );
     }
 
@@ -109,17 +162,55 @@ public final class StringArrayArgument<C> extends CommandArgument<C, String[]> {
      */
     public static final class StringArrayParser<C> implements ArgumentParser<C, String[]> {
 
+        private static final Pattern FLAG_PATTERN = Pattern.compile("(-[A-Za-z_\\-0-9])|(--[A-Za-z_\\-0-9]*)");
+
+        private final boolean flagYielding;
+
+        /**
+         * Construct a new string array parser.
+         */
+        public StringArrayParser() {
+            this.flagYielding = false;
+        }
+
+        /**
+         * Construct a new string array parser.
+         *
+         * @param flagYielding Whether the parser should stop parsing when encountering a potential flag
+         * @since 1.7.0
+         */
+        public StringArrayParser(final boolean flagYielding) {
+            this.flagYielding = flagYielding;
+        }
+
         @Override
         public @NonNull ArgumentParseResult<String @NonNull []> parse(
                 final @NonNull CommandContext<@NonNull C> commandContext,
                 final @NonNull Queue<@NonNull String> inputQueue
         ) {
+            if (this.flagYielding) {
+                final List<String> result = new LinkedList<>();
+                final int size = inputQueue.size();
+
+                for (int i = 0; i < size; i++) {
+                    final String string = inputQueue.peek();
+                    if (string == null || FLAG_PATTERN.matcher(string).matches()) {
+                        break;
+                    }
+                    inputQueue.remove();
+
+                    result.add(string);
+                }
+
+                return ArgumentParseResult.success(result.toArray(new String[0]));
+            } else {
                 final String[] result = new String[inputQueue.size()];
                 for (int i = 0; i < result.length; i++) {
                     result[i] = inputQueue.remove();
                 }
                 return ArgumentParseResult.success(result);
             }
+        }
 
     }
 

cloud-core/src/test/java/cloud/commandframework/CommandSuggestionsTest.java

@@ -28,6 +28,7 @@ import cloud.commandframework.arguments.standard.BooleanArgument;
 import cloud.commandframework.arguments.standard.EnumArgument;
 import cloud.commandframework.arguments.standard.IntegerArgument;
 import cloud.commandframework.arguments.standard.StringArgument;
+import cloud.commandframework.arguments.standard.StringArrayArgument;
 import cloud.commandframework.types.tuples.Pair;
 import cloud.commandframework.types.tuples.Triplet;
 import java.util.Arrays;
@@ -38,6 +39,7 @@ import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
 import static cloud.commandframework.util.TestUtils.createManager;
+import static com.google.common.truth.Truth.assertThat;
 
 public class CommandSuggestionsTest {
 
@@ -394,6 +396,107 @@ public class CommandSuggestionsTest {
         Assertions.assertEquals(Collections.singletonList("later"), suggestions6);
     }
 
+    @Test
+    void testFlagYieldingGreedyStringFollowedByFlagArgument() {
+        // Arrange
+        final CommandManager<TestCommandSender> manager = createManager();
+        manager.command(
+                manager.commandBuilder("command")
+                        .argument(
+                                StringArgument.<TestCommandSender>newBuilder("string")
+                                        .greedyFlagYielding()
+                                        .withSuggestionsProvider((context, input) -> Collections.singletonList("hello"))
+                                        .build()
+                        ).flag(manager.flagBuilder("flag").withAliases("f").build())
+                        .flag(manager.flagBuilder("flag2").build())
+        );
+
+        // Act
+        final List<String> suggestions1 = manager.suggest(
+                new TestCommandSender(),
+                "command "
+        );
+        final List<String> suggestions2 = manager.suggest(
+                new TestCommandSender(),
+                "command hel"
+        );
+        final List<String> suggestions3 = manager.suggest(
+                new TestCommandSender(),
+                "command hello --"
+        );
+        final List<String> suggestions4 = manager.suggest(
+                new TestCommandSender(),
+                "command hello --f"
+        );
+        final List<String> suggestions5 = manager.suggest(
+                new TestCommandSender(),
+                "command hello -f"
+        );
+        final List<String> suggestions6 = manager.suggest(
+                new TestCommandSender(),
+                "command hello -"
+        );
+
+        // Assert
+        assertThat(suggestions1).containsExactly("hello");
+        assertThat(suggestions2).containsExactly("hello");
+        assertThat(suggestions3).containsExactly("--flag", "--flag2");
+        assertThat(suggestions4).containsExactly("--flag", "--flag2");
+        assertThat(suggestions5).containsExactly("-f");
+        assertThat(suggestions6).containsExactly("hello");
+    }
+
+    @Test
+    void testFlagYieldingStringArrayFollowedByFlagArgument() {
+        // Arrange
+        final CommandManager<TestCommandSender> manager = createManager();
+        manager.command(
+                manager.commandBuilder("command")
+                        .argument(
+                                StringArrayArgument.of(
+                                        "array",
+                                        true,
+                                        (context, input) -> Collections.emptyList()
+                                )
+                        ).flag(manager.flagBuilder("flag").withAliases("f").build())
+                        .flag(manager.flagBuilder("flag2").build())
+        );
+
+        // Act
+        final List<String> suggestions1 = manager.suggest(
+                new TestCommandSender(),
+                "command "
+        );
+        final List<String> suggestions2 = manager.suggest(
+                new TestCommandSender(),
+                "command hello"
+        );
+        final List<String> suggestions3 = manager.suggest(
+                new TestCommandSender(),
+                "command hello --"
+        );
+        final List<String> suggestions4 = manager.suggest(
+                new TestCommandSender(),
+                "command hello --f"
+        );
+        final List<String> suggestions5 = manager.suggest(
+                new TestCommandSender(),
+                "command hello -f"
+        );
+        final List<String> suggestions6 = manager.suggest(
+                new TestCommandSender(),
+                "command hello -"
+        );
+
+        // Assert
+        assertThat(suggestions1).isEmpty();
+        assertThat(suggestions2).isEmpty();
+        assertThat(suggestions3).containsExactly("--flag", "--flag2");
+        assertThat(suggestions4).containsExactly("--flag", "--flag2");
+        assertThat(suggestions5).containsExactly("-f");
+        assertThat(suggestions6).isEmpty();
+    }
+
     public enum TestEnum {
         FOO,
         BAR

cloud-core/src/test/java/cloud/commandframework/arguments/standard/StringArrayParserTest.java

@@ -26,6 +26,7 @@ package cloud.commandframework.arguments.standard;
 import cloud.commandframework.TestCommandSender;
 import cloud.commandframework.arguments.parser.ArgumentParseResult;
 import cloud.commandframework.context.CommandContext;
+import java.util.Collections;
 import java.util.LinkedList;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.stream.Collectors;
@@ -78,4 +79,60 @@ class StringArrayParserTest {
 
         assertThat(input).isEmpty();
     }
+
+    @Test
+    void Parse_GreedyFlagAwareLongFormFlag_EndsAfterFlag() {
+        // Arrange
+        final StringArrayArgument.StringArrayParser<TestCommandSender> parser = new StringArrayArgument.StringArrayParser<>(true);
+        final LinkedList<String> input = ArgumentTestHelper.linkedListOf(
+                "this",
+                "is",
+                "a",
+                "string",
+                "--flag",
+                "more",
+                "flag",
+                "content"
+        );
+
+        // Act
+        final ArgumentParseResult<String[]> result = parser.parse(
+                this.context,
+                input
+        );
+
+        // Assert
+        assertThat(result.getFailure()).isEmpty();
+        assertThat(result.getParsedValue()).hasValue(new String[] {"this", "is", "a", "string"});
+
+        assertThat(input).containsExactly("--flag", "more", "flag", "content");
+    }
+
+    @Test
+    void Parse_GreedyFlagAwareShortFormFlag_EndsAfterFlag() {
+        // Arrange
+        final StringArrayArgument.StringArrayParser<TestCommandSender> parser = new StringArrayArgument.StringArrayParser<>(true);
+        final LinkedList<String> input = ArgumentTestHelper.linkedListOf(
+                "this",
+                "is",
+                "a",
+                "string",
+                "-f",
+                "-l",
+                "-a",
+                "-g"
+        );
+
+        // Act
+        final ArgumentParseResult<String[]> result = parser.parse(
+                this.context,
+                input
+        );
+
+        // Assert
+        assertThat(result.getFailure()).isEmpty();
+        assertThat(result.getParsedValue()).hasValue(new String[] {"this", "is", "a", "string"});
+
+        assertThat(input).containsExactly("-f", "-l", "-a", "-g");
+    }
 }

cloud-core/src/test/java/cloud/commandframework/arguments/standard/StringParserTest.java

@@ -0,0 +1,106 @@
+//
+// MIT License
+//
+// Copyright (c) 2021 Alexander Söderberg & Contributors
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+package cloud.commandframework.arguments.standard;
+
+import cloud.commandframework.TestCommandSender;
+import cloud.commandframework.arguments.parser.ArgumentParseResult;
+import cloud.commandframework.context.CommandContext;
+import java.util.Collections;
+import java.util.LinkedList;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.Truth8.assertThat;
+
+@ExtendWith(MockitoExtension.class)
+class StringParserTest {
+
+    @Mock
+    private CommandContext<TestCommandSender> context;
+
+    @Test
+    void Parse_GreedyFlagAwareLongFormFlag_EndsAfterFlag() {
+        // Arrange
+        final StringArgument.StringParser<TestCommandSender> parser = new StringArgument.StringParser<>(
+                StringArgument.StringMode.GREEDY_FLAG_YIELDING,
+                (context, input) -> Collections.emptyList()
+        );
+        final LinkedList<String> input = ArgumentTestHelper.linkedListOf(
+                "this",
+                "is",
+                "a",
+                "string",
+                "--flag",
+                "more",
+                "flag",
+                "content"
+        );
+
+        // Act
+        final ArgumentParseResult<String> result = parser.parse(
+                this.context,
+                input
+        );
+
+        // Assert
+        assertThat(result.getFailure()).isEmpty();
+        assertThat(result.getParsedValue()).hasValue("this is a string");
+
+        assertThat(input).containsExactly("--flag", "more", "flag", "content");
+    }
+
+    @Test
+    void Parse_GreedyFlagAwareShortFormFlag_EndsAfterFlag() {
+        // Arrange
+        final StringArgument.StringParser<TestCommandSender> parser = new StringArgument.StringParser<>(
+                StringArgument.StringMode.GREEDY_FLAG_YIELDING,
+                (context, input) -> Collections.emptyList()
+        );
+        final LinkedList<String> input = ArgumentTestHelper.linkedListOf(
+                "this",
+                "is",
+                "a",
+                "string",
+                "-f",
+                "-l",
+                "-a",
+                "-g"
+        );
+
+        // Act
+        final ArgumentParseResult<String> result = parser.parse(
+                this.context,
+                input
+        );
+
+        // Assert
+        assertThat(result.getFailure()).isEmpty();
+        assertThat(result.getParsedValue()).hasValue("this is a string");
+
+        assertThat(input).containsExactly("-f", "-l", "-a", "-g");
+    }
+}

cloud-core/src/test/java/cloud/commandframework/issue/Issue321.java

@@ -0,0 +1,83 @@
+//
+// MIT License
+//
+// Copyright (c) 2021 Alexander Söderberg & Contributors
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+package cloud.commandframework.issue;
+
+import cloud.commandframework.CommandManager;
+import cloud.commandframework.TestCommandSender;
+import cloud.commandframework.arguments.flags.FlagContext;
+import cloud.commandframework.arguments.standard.StringArrayArgument;
+import cloud.commandframework.context.CommandContext;
+import cloud.commandframework.execution.CommandResult;
+import java.util.Collections;
+import org.junit.jupiter.api.Test;
+
+import static cloud.commandframework.util.TestUtils.createManager;
+import static com.google.common.truth.Truth8.assertThat;
+
+/**
+ * Test for https://github.com/Incendo/cloud/issues/321.
+ */
+class Issue321 {
+
+    @Test
+    void flagSucceedingFlagWithStringArrayArgument() {
+        // Arrange
+        final CommandManager<TestCommandSender> commandManager = createManager();
+        commandManager.command(
+                commandManager.commandBuilder("command")
+                        .flag(
+                                commandManager.flagBuilder("flag1")
+                                        .withArgument(
+                                                StringArrayArgument.of(
+                                                        "array",
+                                                        true /* flagYielding */,
+                                                        (context, input) -> Collections.emptyList()
+                                                )
+                                        )
+                        ).flag(
+                                commandManager.flagBuilder("flag2")
+                                        .withArgument(
+                                                StringArrayArgument.of(
+                                                        "array",
+                                                        true /* flagYielding */,
+                                                        (context, input) -> Collections.emptyList()
+                                                )
+                                        )
+                        )
+        );
+
+        // Act
+        final CommandResult<TestCommandSender> result = commandManager.executeCommand(
+                new TestCommandSender(),
+                "command --flag1 one two three --flag2 1 2 3"
+        ).join();
+
+        // Assert
+        final CommandContext<TestCommandSender> context = result.getCommandContext();
+        final FlagContext flags = context.flags();
+
+        assertThat(flags.<String[]>getValue("flag1")).hasValue(new String[] {"one", "two", "three"});
+        assertThat(flags.<String[]>getValue("flag2")).hasValue(new String[] {"1", "2", "3"});
+    }
+}