Support for empty symbols, e.g. ''

src/software/amazon/ion/EmptySymbolException.java

@@ -7,7 +7,11 @@
 /**
  * An error caused by a symbol not containing at least one character for
  * its text.
+ *
+ * @deprecated this exception is not used as empty symbols are valid. In cases where null is used as the symbol value it was
+ * replaced by {@link NullPointerException}
  */
+@Deprecated
 public class EmptySymbolException
     extends IonException
 {

src/software/amazon/ion/IonSymbol.java

@@ -50,11 +50,8 @@ public String stringValue()
      * @param value the new value of this symbol;
      * may be <code>null</code> to make this <code>null.symbol</code>.
      *
-     * @throws EmptySymbolException if <code>value</code> is the empty string.
      */
-    public void setValue(String value)
-        throws EmptySymbolException;
-
+    public void setValue(String value);
 
     public IonSymbol clone()
         throws UnknownSymbolException;

src/software/amazon/ion/IonText.java

@@ -42,11 +42,8 @@ public interface IonText
      * @param value the new value of this text value;
      * may be <code>null</code> to make this an Ion null value.
      *
-     * @throws EmptySymbolException if this is an {@link IonSymbol} and
-     * <code>value</code> is the empty string.
      */
-    public void setValue(String value)
-        throws EmptySymbolException;
+    public void setValue(String value);
 
     public IonText clone()
         throws UnknownSymbolException;

src/software/amazon/ion/IonValue.java

@@ -304,8 +304,7 @@ public interface IonValue
      * @param annotations the new annotations.  If null or empty array, then
      *  all annotations are removed.  Any duplicates are preserved.
      *
-     * @throws EmptySymbolException if any of the annotations are null or
-     *  empty string.
+     * @throws NullPointerException if any of the annotations are null
      *
      */
     public void setTypeAnnotations(String... annotations);

src/software/amazon/ion/IonWriter.java

@@ -189,7 +189,6 @@ public interface IonWriter
      * @throws IllegalStateException if the current container isn't a struct,
      * that is, if {@link #isInStruct()} is false.
      * @throws NullPointerException if {@code name} is null.
-     * @throws EmptySymbolException if {@code name} is empty.
      */
     public void setFieldName(String name);
 

src/software/amazon/ion/SymbolTable.java

@@ -253,7 +253,6 @@ public interface SymbolTable
      * {@link #UNKNOWN_SYMBOL_ID} if it's not defined.
      *
      * @throws NullPointerException if {@code name} is null.
-     * @throws EmptySymbolException if {@code name} is empty.
      */
     public int findSymbol(String name);
 

src/software/amazon/ion/ValueFactory.java

@@ -479,7 +479,7 @@ public IonSexp newSexp(IonValue... children)
      * @param value the text of the symbol;
      * may be <code>null</code> to make <code>null.symbol</code>.
      *
-     * @throws EmptySymbolException if <code>value</code> is the empty string.
+     * @throws NullPointerException if <code>value</code> is null.
      */
     public IonSymbol newSymbol(String value);
 

src/software/amazon/ion/impl/IonReaderTextRawX.java

@@ -417,13 +417,8 @@ private final void current_value_is_bool(boolean value)
     }
 
     private final void set_fieldname(SymbolToken sym) {
-        String text = sym.getText();
-        int sid = sym.getSid();
-        if (text != null && text.length() < 1) {
-            parse_error("empty strings are not valid field names");
-        }
-        _field_name = text;
-        _field_name_sid = sid;
+        _field_name = sym.getText();
+        _field_name_sid = sym.getSid();
     }
 
     private final void clear_fieldname() {
@@ -877,10 +872,7 @@ protected final void parse_to_next_value() throws IOException
             case ACTION_LOAD_ANNOTATION:
             {
                 sb = token_contents_load(t);
-                if (sb.length() < 1) {
-                    // this is the case for an empty symbol
-                    parse_error("empty symbols are not valid");
-                }
+
                 trailing_whitespace = _scanner.skip_whitespace();
                 if (!_scanner.skipDoubleColon()) {
                     // unnecessary: set_current_value(sp);

src/software/amazon/ion/impl/IonWriterSystem.java

@@ -20,7 +20,6 @@
 import static software.amazon.ion.impl.PrivateUtils.newSymbolTokens;
 
 import java.io.IOException;
-import software.amazon.ion.EmptySymbolException;
 import software.amazon.ion.IonType;
 import software.amazon.ion.SymbolTable;
 import software.amazon.ion.SymbolToken;
@@ -366,9 +365,9 @@ public final void setFieldName(String name)
         if (!this.isInStruct()) {
             throw new IllegalStateException();
         }
-        if (name.length() == 0) {
-            throw new EmptySymbolException();
-        }
+
+        name.getClass(); // fast null check
+
         _field_name_type = IonType.STRING;
         _field_name = name;
         _field_name_sid = UNKNOWN_SYMBOL_ID;
@@ -383,9 +382,6 @@ public final void setFieldNameSymbol(SymbolToken name)
         String text = name.getText();
         if (text != null)
         {
-            if (text.length() == 0) {
-                throw new EmptySymbolException();
-            }
             _field_name_type = IonType.STRING;
             _field_name = text;
             _field_name_sid = UNKNOWN_SYMBOL_ID;

src/software/amazon/ion/impl/LocalSymbolTable.java

@@ -37,7 +37,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
-import software.amazon.ion.EmptySymbolException;
 import software.amazon.ion.IonCatalog;
 import software.amazon.ion.IonException;
 import software.amazon.ion.IonList;
@@ -333,17 +332,14 @@ private LocalSymbolTable(LocalSymbolTable other, int maxId)
                         IonType type;
                         while ((type = reader.next()) != null)
                         {
-                            String text = null;
+                            final String text;
                             if (type == IonType.STRING)
                             {
-                                // As per the Spec, if any element of
-                                // the list is the empty string or any
-                                // other type, treat it as null
                                 text = reader.stringValue();
-                                if (text != null && text.length() == 0)
-                                {
-                                    text = null;
-                                }
+                            }
+                            else
+                            {
+                                text = null;
                             }
 
                             symbolsList.add(text);
@@ -483,11 +479,6 @@ else if (id < myFirstLocalSid)
 
     public int findSymbol(String name)
     {
-        if (name.length() < 1) // throws NPE if null
-        {
-            throw new EmptySymbolException();
-        }
-
         // Look in system then imports
         int sid = myImportsList.findSymbol(name);
 
@@ -502,8 +493,6 @@ public int findSymbol(String name)
 
     private int findLocalSymbol(String name)
     {
-        assert(name.length() > 0);
-
         Integer isid;
         synchronized (this)
         {
@@ -533,10 +522,7 @@ public synchronized SymbolToken intern(String text)
 
     public SymbolToken find(String text)
     {
-        if (text.length() < 1)
-        {
-            throw new EmptySymbolException();
-        }
+        text.getClass(); // fast null check
 
         // Look in system then imports
         SymbolToken symTok = myImportsList.find(text);
@@ -566,10 +552,9 @@ public SymbolToken find(String text)
 
     private static final void validateSymbol(String name)
     {
-        if (name == null || name.length() < 1)
+        if (name == null)
         {
-            String message = "symbols must contain 1 or more characters";
-            throw new IllegalArgumentException(message);
+            throw new IllegalArgumentException("symbols must not be null");
         }
         for (int i = 0; i < name.length(); ++i)
         {
@@ -607,8 +592,6 @@ private static final void validateSymbol(String name)
      */
     private int putSymbol(String symbolName)
     {
-        assert symbolName.length() != 0;
-
         if (isReadOnly)
         {
             throw new ReadOnlyValueException(SymbolTable.class);

src/software/amazon/ion/impl/PrivateIonTextAppender.java

@@ -29,7 +29,6 @@
 import java.nio.CharBuffer;
 import java.nio.charset.Charset;
 import software.amazon.ion.Decimal;
-import software.amazon.ion.EmptySymbolException;
 import software.amazon.ion.impl.Base64Encoder.TextStream;
 import software.amazon.ion.system.IonTextWriterBuilder;
 import software.amazon.ion.util.PrivateFastAppendable;
@@ -410,6 +409,12 @@ public static boolean isIdentifierKeyword(CharSequence text)
     {
         int pos = 0;
         int valuelen = text.length();
+
+        if(valuelen == 0)
+        {
+            return false;
+        }
+
         boolean keyword = false;
 
         // there has to be at least 1 character or we wouldn't be here
@@ -473,51 +478,51 @@ else if (valuelen == 3 // 'n'
      *
      * @throws NullPointerException
      *         if <code>symbol</code> is <code>null</code>.
-     * @throws EmptySymbolException if <code>symbol</code> is empty.
      */
     public static boolean symbolNeedsQuoting(CharSequence symbol,
                                              boolean      quoteOperators)
     {
         int length = symbol.length();
-        if (length == 0) {
-            throw new EmptySymbolException();
-        }
 
-        // If the symbol's text matches an Ion keyword, we must quote it.
-        // Eg, the symbol 'false' must be rendered quoted.
-        if (! isIdentifierKeyword(symbol))
+        // If the symbol's text matches an Ion keyword or it's an empty symbol, we must quote it.
+        // Eg, the symbol 'false' and '' must be rendered quoted.
+        if(length == 0 || isIdentifierKeyword(symbol))
         {
-            char c = symbol.charAt(0);
-            // Surrogates are neither identifierStart nor operatorPart, so the
-            // first one we hit will fall through and return true.
-            // TODO test that
+            return true;
+        }
 
-            if (!quoteOperators && isOperatorPart(c))
-            {
-                for (int ii = 0; ii < length; ii++) {
-                    c = symbol.charAt(ii);
-                    // We don't need to look for escapes since all
-                    // operator characters are ASCII.
-                    if (!isOperatorPart(c)) {
-                        return true;
-                    }
+        char c = symbol.charAt(0);
+
+        // Surrogates are neither identifierStart nor operatorPart, so the
+        // first one we hit will fall through and return true.
+        // TODO test that
+
+        if (!quoteOperators && isOperatorPart(c))
+        {
+            for (int ii = 0; ii < length; ii++) {
+                c = symbol.charAt(ii);
+                // We don't need to look for escapes since all
+                // operator characters are ASCII.
+                if (!isOperatorPart(c)) {
+                    return true;
                 }
-                return false;
             }
-            else if (isIdentifierStart(c))
-            {
-                for (int ii = 0; ii < length; ii++) {
-                    c = symbol.charAt(ii);
-                    if ((c == '\'' || c < 32 || c > 126)
-                        || !isIdentifierPart(c))
-                    {
-                        return true;
-                    }
+            return false;
+        }
+        else if (isIdentifierStart(c))
+        {
+            for (int ii = 0; ii < length; ii++) {
+                c = symbol.charAt(ii);
+                if ((c == '\'' || c < 32 || c > 126)
+                    || !isIdentifierPart(c))
+                {
+                    return true;
                 }
-                return false;
             }
+            return false;
         }
 
+        // quote by default
         return true;
     }
 
@@ -534,10 +539,6 @@ public final void printSymbol(CharSequence text)
         {
             appendAscii("null.symbol");
         }
-        else if (text.length() == 0)
-        {
-            throw new EmptySymbolException();
-        }
         else if (symbolNeedsQuoting(text, true)) {
             appendAscii('\'');
             printCodePoints(text, SYMBOL_ESCAPE_CODES);
@@ -561,10 +562,6 @@ public final void printQuotedSymbol(CharSequence text)
         {
             appendAscii("null.symbol");
         }
-        else if (text.length() == 0)
-        {
-            throw new EmptySymbolException();
-        }
         else
         {
             appendAscii('\'');