Use chained exceptions consistently throughout the code base

In some places of our code, we respond to an exception by throwing
another exception.

In such a situation, it is good practice to _chain_ the exceptions by
passing the initial exception as a `cause` to the next exception. This
is because it provides more information to higher-level exception
handlers, allowing them to e.g. provide more meaningful stack traces
that show how the exception is handled and transformed as it is
propagated through the call stack.

However, certain places in our code base do not use exception chaining
when they could. These were discovered by grepping the code base for
`\bthrow\b` and seeing if any of the thrown exceptions fit the criteria
described above.

Let's fix them to use chained exceptions.

See https://docs.oracle.com/javase/tutorial/essential/exceptions/chained.html
for more information on chained exceptions.

src/main/java/seedu/address/logic/commands/AddCommand.java

@@ -54,7 +54,7 @@ public CommandResult execute() throws CommandException {
             model.commitAddressBook();
             return new CommandResult(String.format(MESSAGE_SUCCESS, toAdd));
         } catch (DuplicatePersonException e) {
-            throw new CommandException(MESSAGE_DUPLICATE_PERSON);
+            throw new CommandException(MESSAGE_DUPLICATE_PERSON, e);
         }
 
     }

src/main/java/seedu/address/logic/commands/DeleteCommand.java

@@ -42,7 +42,7 @@ public CommandResult execute() throws CommandException {
             model.deletePerson(personToDelete);
             model.commitAddressBook();
         } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("The target person cannot be missing");
+            throw new AssertionError("The target person cannot be missing", pnfe);
         }
 
         return new CommandResult(String.format(MESSAGE_DELETE_PERSON_SUCCESS, personToDelete));

src/main/java/seedu/address/logic/commands/EditCommand.java

@@ -80,9 +80,9 @@ public CommandResult execute() throws CommandException {
         try {
             model.updatePerson(personToEdit, editedPerson);
         } catch (DuplicatePersonException dpe) {
-            throw new CommandException(MESSAGE_DUPLICATE_PERSON);
+            throw new CommandException(MESSAGE_DUPLICATE_PERSON, dpe);
         } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("The target person cannot be missing");
+            throw new AssertionError("The target person cannot be missing", pnfe);
         }
         model.updateFilteredPersonList(PREDICATE_SHOW_ALL_PERSONS);
         model.commitAddressBook();

src/main/java/seedu/address/logic/commands/exceptions/CommandException.java

@@ -7,4 +7,11 @@ public class CommandException extends Exception {
     public CommandException(String message) {
         super(message);
     }
+
+    /**
+     * Constructs a new {@code CommandException} with the specified detail {@code message} and {@code cause}.
+     */
+    public CommandException(String message, Throwable cause) {
+        super(message, cause);
+    }
 }

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

@@ -22,7 +22,7 @@ public DeleteCommand parse(String args) throws ParseException {
             return new DeleteCommand(index);
         } catch (ParseException pe) {
             throw new ParseException(
-                    String.format(MESSAGE_INVALID_COMMAND_FORMAT, DeleteCommand.MESSAGE_USAGE));
+                    String.format(MESSAGE_INVALID_COMMAND_FORMAT, DeleteCommand.MESSAGE_USAGE), pe);
         }
     }
 

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

@@ -39,7 +39,7 @@ public EditCommand parse(String args) throws ParseException {
         try {
             index = ParserUtil.parseIndex(argMultimap.getPreamble());
         } catch (ParseException pe) {
-            throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, EditCommand.MESSAGE_USAGE));
+            throw new ParseException(String.format(MESSAGE_INVALID_COMMAND_FORMAT, EditCommand.MESSAGE_USAGE), pe);
         }
 
         EditPersonDescriptor editPersonDescriptor = new EditPersonDescriptor();

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

@@ -22,7 +22,7 @@ public SelectCommand parse(String args) throws ParseException {
             return new SelectCommand(index);
         } catch (ParseException pe) {
             throw new ParseException(
-                    String.format(MESSAGE_INVALID_COMMAND_FORMAT, SelectCommand.MESSAGE_USAGE));
+                    String.format(MESSAGE_INVALID_COMMAND_FORMAT, SelectCommand.MESSAGE_USAGE), pe);
         }
     }
 }

src/main/java/seedu/address/model/AddressBook.java

@@ -54,7 +54,7 @@ public void resetData(ReadOnlyAddressBook newData) {
         try {
             setPersons(newData.getPersonList());
         } catch (DuplicatePersonException e) {
-            throw new AssertionError("AddressBooks should not have duplicate persons");
+            throw new AssertionError("AddressBooks should not have duplicate persons", e);
         }
     }
 

src/main/java/seedu/address/storage/XmlFileStorage.java

@@ -20,7 +20,7 @@ public static void saveDataToFile(Path file, XmlSerializableAddressBook addressB
         try {
             XmlUtil.saveDataToFile(file, addressBook);
         } catch (JAXBException e) {
-            throw new AssertionError("Unexpected exception " + e.getMessage());
+            throw new AssertionError("Unexpected exception " + e.getMessage(), e);
         }
     }
 

src/test/java/seedu/address/TestApp.java

@@ -77,9 +77,9 @@ public AddressBook readStorageAddressBook() {
         try {
             return new AddressBook(storage.readAddressBook().get());
         } catch (DataConversionException dce) {
-            throw new AssertionError("Data is not in the AddressBook format.");
+            throw new AssertionError("Data is not in the AddressBook format.", dce);
         } catch (IOException ioe) {
-            throw new AssertionError("Storage file cannot be found.");
+            throw new AssertionError("Storage file cannot be found.", ioe);
         }
     }
 

src/test/java/seedu/address/testutil/AddressBookBuilder.java

@@ -28,7 +28,7 @@ public AddressBookBuilder withPerson(Person person) {
         try {
             addressBook.addPerson(person);
         } catch (DuplicatePersonException dpe) {
-            throw new IllegalArgumentException("person is expected to be unique.");
+            throw new IllegalArgumentException("person is expected to be unique.", dpe);
         }
         return this;
     }

src/test/java/seedu/address/testutil/Assert.java

@@ -35,7 +35,7 @@ public static void assertThrows(Class<? extends Throwable> expectedException, St
                 return;
             }
 
-            throw new AssertionError(errorMessage);
+            throw new AssertionError(errorMessage, actualException);
         }
 
         throw new AssertionError(String.format(

src/test/java/seedu/address/testutil/TypicalPersons.java

@@ -69,7 +69,7 @@ public static AddressBook getTypicalAddressBook() {
             try {
                 ab.addPerson(person);
             } catch (DuplicatePersonException e) {
-                throw new AssertionError("not possible");
+                throw new AssertionError("not possible", e);
             }
         }
         return ab;

src/test/java/systemtests/AddCommandSystemTest.java

@@ -210,7 +210,7 @@ private void assertCommandSuccess(String command, Person toAdd) {
         try {
             expectedModel.addPerson(toAdd);
         } catch (DuplicatePersonException dpe) {
-            throw new IllegalArgumentException("toAdd already exists in the model.");
+            throw new IllegalArgumentException("toAdd already exists in the model.", dpe);
         }
         String expectedResultMessage = String.format(AddCommand.MESSAGE_SUCCESS, toAdd);
 

src/test/java/systemtests/AddressBookSystemTest.java

@@ -218,7 +218,7 @@ protected void assertSelectedCardChanged(Index expectedSelectedCardIndex) {
         try {
             expectedUrl = new URL(BrowserPanel.SEARCH_PAGE_URL + selectedCardName.replaceAll(" ", "%20"));
         } catch (MalformedURLException mue) {
-            throw new AssertionError("URL expected to be valid.");
+            throw new AssertionError("URL expected to be valid.", mue);
         }
         assertEquals(expectedUrl, getBrowserPanel().getLoadedUrl());
 

src/test/java/systemtests/DeleteCommandSystemTest.java

@@ -121,7 +121,7 @@ private Person removePerson(Model model, Index index) {
         try {
             model.deletePerson(targetPerson);
         } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("targetPerson is retrieved from model.");
+            throw new AssertionError("targetPerson is retrieved from model.", pnfe);
         }
         return targetPerson;
     }

src/test/java/systemtests/EditCommandSystemTest.java

@@ -242,7 +242,7 @@ private void assertCommandSuccess(String command, Index toEdit, Person editedPer
             expectedModel.updateFilteredPersonList(PREDICATE_SHOW_ALL_PERSONS);
         } catch (DuplicatePersonException | PersonNotFoundException e) {
             throw new IllegalArgumentException(
-                    "editedPerson is a duplicate in expectedModel, or it isn't found in the model.");
+                    "editedPerson is a duplicate in expectedModel, or it isn't found in the model.", e);
         }
 
         assertCommandSuccess(command, expectedModel,

src/test/java/systemtests/SystemTestSetupHelper.java

@@ -26,7 +26,7 @@ public TestApp setupApplication(Supplier<ReadOnlyAddressBook> addressBook, Path
             FxToolkit.registerStage(Stage::new);
             FxToolkit.setupApplication(() -> testApp = new TestApp(addressBook, saveFileLocation));
         } catch (TimeoutException te) {
-            throw new AssertionError("Application takes too long to set up.");
+            throw new AssertionError("Application takes too long to set up.", te);
         }
 
         return testApp;
@@ -55,7 +55,7 @@ public MainWindowHandle setupMainWindowHandle() {
             });
             FxToolkit.showStage();
         } catch (TimeoutException te) {
-            throw new AssertionError("Stage takes too long to set up.");
+            throw new AssertionError("Stage takes too long to set up.", te);
         }
 
         return mainWindowHandle;
@@ -68,7 +68,7 @@ public void tearDownStage() {
         try {
             FxToolkit.cleanupStages();
         } catch (TimeoutException te) {
-            throw new AssertionError("Stage takes too long to tear down.");
+            throw new AssertionError("Stage takes too long to tear down.", te);
         }
     }
 }