Remove support for repeated parameters in commands

If a single-valued parameter is repeated multiple times in a command,
only the last occurrence is taken. This allows the user to correct a
mistake in a parameter value by simply typing it again, which may be
faster than moving the cursor back to the original parameter values and
editing it. This feature serves as a good example of 'going the extra
mile to optimize the application for target users' (i.e., users who can
type fast).
However, this feature can cause certain user errors to go unnoticed
e.g., unintended repetition caused by a typo in parameter name

Alternatives considered:
(a) Retain current behavior but give a friendly warning to the user
    that a parameter was 'overridden'.
(b) Remove this feature i.e., treat repeated single-valued parameters
    as an error, and reject the command with an error message.

Alternative (a) requires significantly more complicated code (see #181),
steepening the learning curve for for new programmers. Given that this
application is primarily meant for training novice programmers, the
impact on the learning curve is not worth the benefit of retaining this
feature.

Therefore, let's do option (b).

docs/UserGuide.md

@@ -57,9 +57,6 @@ AddressBook Level 3 (AB3) is a **desktop app for managing contacts, optimized fo
 * Parameters can be in any order.<br>
   e.g. if the command specifies `n/NAME p/PHONE_NUMBER`, `p/PHONE_NUMBER n/NAME` is also acceptable.
 
-* If a parameter is expected only once in the command but you specified it multiple times, only the last occurrence of the parameter will be taken.<br>
-  e.g. if you specify `p/12341234 p/56785678`, only `p/56785678` will be taken.
-
 * Extraneous parameters for commands that do not take in parameters (such as `help`, `list`, `exit` and `clear`) will be ignored.<br>
   e.g. if the command specifies `help 123`, it will be interpreted as `help`.
 

src/main/java/seedu/address/logic/Messages.java

@@ -1,5 +1,10 @@
 package seedu.address.logic;
 
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import seedu.address.logic.parser.Prefix;
 import seedu.address.model.person.Person;
 
 /**
@@ -11,6 +16,20 @@ public class Messages {
     public static final String MESSAGE_INVALID_COMMAND_FORMAT = "Invalid command format! \n%1$s";
     public static final String MESSAGE_INVALID_PERSON_DISPLAYED_INDEX = "The person index provided is invalid";
     public static final String MESSAGE_PERSONS_LISTED_OVERVIEW = "%1$d persons listed!";
+    public static final String MESSAGE_DUPLICATE_FIELDS =
+                "Multiple values specified for the following single-valued field(s): ";
+
+    /**
+     * Returns an error message indicating the duplicate prefixes.
+     */
+    public static String getErrorMessageForDuplicatePrefixes(Prefix... duplicatePrefixes) {
+        assert duplicatePrefixes.length > 0;
+
+        Set<String> duplicateFields =
+                Stream.of(duplicatePrefixes).map(Prefix::toString).collect(Collectors.toSet());
+
+        return MESSAGE_DUPLICATE_FIELDS + String.join(" ", duplicateFields);
+    }
 
     /**
      * Formats the {@code person} for display to the user.

src/main/java/seedu/address/logic/parser/AddCommandParser.java

@@ -38,6 +38,7 @@ public AddCommand parse(String args) throws ParseException {
             throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, AddCommand.MESSAGE_USAGE));
         }
 
+        argMultimap.verifyNoDuplicatePrefixesFor(PREFIX_NAME, PREFIX_PHONE, PREFIX_EMAIL, PREFIX_ADDRESS);
         Name name = ParserUtil.parseName(argMultimap.getValue(PREFIX_NAME).get());
         Phone phone = ParserUtil.parsePhone(argMultimap.getValue(PREFIX_PHONE).get());
         Email email = ParserUtil.parseEmail(argMultimap.getValue(PREFIX_EMAIL).get());

src/main/java/seedu/address/logic/parser/ArgumentMultimap.java

@@ -5,6 +5,10 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.stream.Stream;
+
+import seedu.address.logic.Messages;
+import seedu.address.logic.parser.exceptions.ParseException;
 
 /**
  * Stores mapping of prefixes to their respective arguments.
@@ -57,4 +61,18 @@ public List<String> getAllValues(Prefix prefix) {
     public String getPreamble() {
         return getValue(new Prefix("")).orElse("");
     }
+
+    /**
+     * Throws a {@code ParseException} if any of the prefixes given in {@code prefixes} appeared more than
+     * once among the arguments.
+     */
+    public void verifyNoDuplicatePrefixesFor(Prefix... prefixes) throws ParseException {
+        Prefix[] duplicatedPrefixes = Stream.of(prefixes).distinct()
+                .filter(prefix -> argMultimap.containsKey(prefix) && argMultimap.get(prefix).size() > 1)
+                .toArray(Prefix[]::new);
+
+        if (duplicatedPrefixes.length > 0) {
+            throw new ParseException(Messages.getErrorMessageForDuplicatePrefixes(duplicatedPrefixes));
+        }
+    }
 }

src/main/java/seedu/address/logic/parser/EditCommandParser.java

@@ -42,7 +42,10 @@ public EditCommand parse(String args) throws ParseException {
             throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, EditCommand.MESSAGE_USAGE), pe);
         }
 
+        argMultimap.verifyNoDuplicatePrefixesFor(PREFIX_NAME, PREFIX_PHONE, PREFIX_EMAIL, PREFIX_ADDRESS);
+
         EditPersonDescriptor editPersonDescriptor = new EditPersonDescriptor();
+
         if (argMultimap.getValue(PREFIX_NAME).isPresent()) {
             editPersonDescriptor.setName(ParserUtil.parseName(argMultimap.getValue(PREFIX_NAME).get()));
         }

src/test/java/seedu/address/logic/parser/AddCommandParserTest.java

@@ -24,13 +24,18 @@
 import static seedu.address.logic.commands.CommandTestUtil.VALID_PHONE_BOB;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_TAG_FRIEND;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_TAG_HUSBAND;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_ADDRESS;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_EMAIL;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_NAME;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_PHONE;
 import static seedu.address.logic.parser.CommandParserTestUtil.assertParseFailure;
 import static seedu.address.logic.parser.CommandParserTestUtil.assertParseSuccess;
 import static seedu.address.testutil.TypicalPersons.AMY;
 import static seedu.address.testutil.TypicalPersons.BOB;
 
 import org.junit.jupiter.api.Test;
 
+import seedu.address.logic.Messages;
 import seedu.address.logic.commands.AddCommand;
 import seedu.address.model.person.Address;
 import seedu.address.model.person.Email;
@@ -51,27 +56,77 @@ public void parse_allFieldsPresent_success() {
         assertParseSuccess(parser, PREAMBLE_WHITESPACE + NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB
                 + ADDRESS_DESC_BOB + TAG_DESC_FRIEND, new AddCommand(expectedPerson));
 
-        // multiple names - last name accepted
-        assertParseSuccess(parser, NAME_DESC_AMY + NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB
-                + ADDRESS_DESC_BOB + TAG_DESC_FRIEND, new AddCommand(expectedPerson));
-
-        // multiple phones - last phone accepted
-        assertParseSuccess(parser, NAME_DESC_BOB + PHONE_DESC_AMY + PHONE_DESC_BOB + EMAIL_DESC_BOB
-                + ADDRESS_DESC_BOB + TAG_DESC_FRIEND, new AddCommand(expectedPerson));
-
-        // multiple emails - last email accepted
-        assertParseSuccess(parser, NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_AMY + EMAIL_DESC_BOB
-                + ADDRESS_DESC_BOB + TAG_DESC_FRIEND, new AddCommand(expectedPerson));
-
-        // multiple addresses - last address accepted
-        assertParseSuccess(parser, NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB + ADDRESS_DESC_AMY
-                + ADDRESS_DESC_BOB + TAG_DESC_FRIEND, new AddCommand(expectedPerson));
 
         // multiple tags - all accepted
         Person expectedPersonMultipleTags = new PersonBuilder(BOB).withTags(VALID_TAG_FRIEND, VALID_TAG_HUSBAND)
                 .build();
-        assertParseSuccess(parser, NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB + ADDRESS_DESC_BOB
-                + TAG_DESC_HUSBAND + TAG_DESC_FRIEND, new AddCommand(expectedPersonMultipleTags));
+        assertParseSuccess(parser,
+                NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB + ADDRESS_DESC_BOB + TAG_DESC_HUSBAND + TAG_DESC_FRIEND,
+                new AddCommand(expectedPersonMultipleTags));
+    }
+
+    @Test
+    public void parse_repeatedNonTagValue_failure() {
+        String validExpectedPersonString = NAME_DESC_BOB + PHONE_DESC_BOB + EMAIL_DESC_BOB
+                + ADDRESS_DESC_BOB + TAG_DESC_FRIEND;
+
+        // multiple names
+        assertParseFailure(parser, NAME_DESC_AMY + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_NAME));
+
+        // multiple phones
+        assertParseFailure(parser, PHONE_DESC_AMY + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE));
+
+        // multiple emails
+        assertParseFailure(parser, EMAIL_DESC_AMY + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_EMAIL));
+
+        // multiple addresses
+        assertParseFailure(parser, ADDRESS_DESC_AMY + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_ADDRESS));
+
+        // multiple fields repeated
+        assertParseFailure(parser,
+                validExpectedPersonString + PHONE_DESC_AMY + EMAIL_DESC_AMY + NAME_DESC_AMY + ADDRESS_DESC_AMY
+                        + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_NAME, PREFIX_ADDRESS, PREFIX_EMAIL, PREFIX_PHONE));
+
+        // invalid value followed by valid value
+
+        // invalid name
+        assertParseFailure(parser, INVALID_NAME_DESC + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_NAME));
+
+        // invalid email
+        assertParseFailure(parser, INVALID_EMAIL_DESC + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_EMAIL));
+
+        // invalid phone
+        assertParseFailure(parser, INVALID_PHONE_DESC + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE));
+
+        // invalid address
+        assertParseFailure(parser, INVALID_ADDRESS_DESC + validExpectedPersonString,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_ADDRESS));
+
+        // valid value followed by invalid value
+
+        // invalid name
+        assertParseFailure(parser, validExpectedPersonString + INVALID_NAME_DESC,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_NAME));
+
+        // invalid email
+        assertParseFailure(parser, validExpectedPersonString + INVALID_EMAIL_DESC,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_EMAIL));
+
+        // invalid phone
+        assertParseFailure(parser, validExpectedPersonString + INVALID_PHONE_DESC,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE));
+
+        // invalid address
+        assertParseFailure(parser, validExpectedPersonString + INVALID_ADDRESS_DESC,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_ADDRESS));
     }
 
     @Test

src/test/java/seedu/address/logic/parser/EditCommandParserTest.java

@@ -16,14 +16,15 @@
 import static seedu.address.logic.commands.CommandTestUtil.TAG_DESC_FRIEND;
 import static seedu.address.logic.commands.CommandTestUtil.TAG_DESC_HUSBAND;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_ADDRESS_AMY;
-import static seedu.address.logic.commands.CommandTestUtil.VALID_ADDRESS_BOB;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_EMAIL_AMY;
-import static seedu.address.logic.commands.CommandTestUtil.VALID_EMAIL_BOB;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_NAME_AMY;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_PHONE_AMY;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_PHONE_BOB;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_TAG_FRIEND;
 import static seedu.address.logic.commands.CommandTestUtil.VALID_TAG_HUSBAND;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_ADDRESS;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_EMAIL;
+import static seedu.address.logic.parser.CliSyntax.PREFIX_PHONE;
 import static seedu.address.logic.parser.CliSyntax.PREFIX_TAG;
 import static seedu.address.logic.parser.CommandParserTestUtil.assertParseFailure;
 import static seedu.address.logic.parser.CommandParserTestUtil.assertParseSuccess;
@@ -34,6 +35,7 @@
 import org.junit.jupiter.api.Test;
 
 import seedu.address.commons.core.index.Index;
+import seedu.address.logic.Messages;
 import seedu.address.logic.commands.EditCommand;
 import seedu.address.logic.commands.EditCommand.EditPersonDescriptor;
 import seedu.address.model.person.Address;
@@ -90,10 +92,6 @@ public void parse_invalidValue_failure() {
         // invalid phone followed by valid email
         assertParseFailure(parser, "1" + INVALID_PHONE_DESC + EMAIL_DESC_AMY, Phone.MESSAGE_CONSTRAINTS);
 
-        // valid phone followed by invalid phone. The test case for invalid phone followed by valid phone
-        // is tested at {@code parse_invalidValueFollowedByValidValue_success()}
-        assertParseFailure(parser, "1" + PHONE_DESC_BOB + INVALID_PHONE_DESC, Phone.MESSAGE_CONSTRAINTS);
-
         // while parsing {@code PREFIX_TAG} alone will reset the tags of the {@code Person} being edited,
         // parsing it together with a valid tag results in error
         assertParseFailure(parser, "1" + TAG_DESC_FRIEND + TAG_DESC_HUSBAND + TAG_EMPTY, Tag.MESSAGE_CONSTRAINTS);
@@ -166,36 +164,35 @@ public void parse_oneFieldSpecified_success() {
     }
 
     @Test
-    public void parse_multipleRepeatedFields_acceptsLast() {
+    public void parse_multipleRepeatedFields_failure() {
+        // More extensive testing of duplicate parameter detections is done in
+        // AddCommandParserTest#parse_repeatedNonTagValue_failure()
+
+        // valid followed by invalid
         Index targetIndex = INDEX_FIRST_PERSON;
-        String userInput = targetIndex.getOneBased() + PHONE_DESC_AMY + ADDRESS_DESC_AMY + EMAIL_DESC_AMY
+        String userInput = targetIndex.getOneBased() + INVALID_PHONE_DESC + PHONE_DESC_BOB;
+
+        assertParseFailure(parser, userInput, Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE));
+
+        // invalid followed by valid
+        userInput = targetIndex.getOneBased() + PHONE_DESC_BOB + INVALID_PHONE_DESC;
+
+        assertParseFailure(parser, userInput, Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE));
+
+        // mulltiple valid fields repeated
+        userInput = targetIndex.getOneBased() + PHONE_DESC_AMY + ADDRESS_DESC_AMY + EMAIL_DESC_AMY
                 + TAG_DESC_FRIEND + PHONE_DESC_AMY + ADDRESS_DESC_AMY + EMAIL_DESC_AMY + TAG_DESC_FRIEND
                 + PHONE_DESC_BOB + ADDRESS_DESC_BOB + EMAIL_DESC_BOB + TAG_DESC_HUSBAND;
 
-        EditPersonDescriptor descriptor = new EditPersonDescriptorBuilder().withPhone(VALID_PHONE_BOB)
-                .withEmail(VALID_EMAIL_BOB).withAddress(VALID_ADDRESS_BOB).withTags(VALID_TAG_FRIEND, VALID_TAG_HUSBAND)
-                .build();
-        EditCommand expectedCommand = new EditCommand(targetIndex, descriptor);
+        assertParseFailure(parser, userInput,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE, PREFIX_EMAIL, PREFIX_ADDRESS));
 
-        assertParseSuccess(parser, userInput, expectedCommand);
-    }
+        // multiple invalid values
+        userInput = targetIndex.getOneBased() + INVALID_PHONE_DESC + INVALID_ADDRESS_DESC + INVALID_EMAIL_DESC
+                + INVALID_PHONE_DESC + INVALID_ADDRESS_DESC + INVALID_EMAIL_DESC;
 
-    @Test
-    public void parse_invalidValueFollowedByValidValue_success() {
-        // no other valid values specified
-        Index targetIndex = INDEX_FIRST_PERSON;
-        String userInput = targetIndex.getOneBased() + INVALID_PHONE_DESC + PHONE_DESC_BOB;
-        EditPersonDescriptor descriptor = new EditPersonDescriptorBuilder().withPhone(VALID_PHONE_BOB).build();
-        EditCommand expectedCommand = new EditCommand(targetIndex, descriptor);
-        assertParseSuccess(parser, userInput, expectedCommand);
-
-        // other valid values specified
-        userInput = targetIndex.getOneBased() + EMAIL_DESC_BOB + INVALID_PHONE_DESC + ADDRESS_DESC_BOB
-                + PHONE_DESC_BOB;
-        descriptor = new EditPersonDescriptorBuilder().withPhone(VALID_PHONE_BOB).withEmail(VALID_EMAIL_BOB)
-                .withAddress(VALID_ADDRESS_BOB).build();
-        expectedCommand = new EditCommand(targetIndex, descriptor);
-        assertParseSuccess(parser, userInput, expectedCommand);
+        assertParseFailure(parser, userInput,
+                Messages.getErrorMessageForDuplicatePrefixes(PREFIX_PHONE, PREFIX_EMAIL, PREFIX_ADDRESS));
     }
 
     @Test