Refactor: Use .equals() instead of equality operator (==) for comparing string constant marker.

As `NOT_SET` is a string constant marker that we set to mark not set values, e.g. for an escape char, it would
be possible to compare for it via the equality operator. However, the python style check doesn't accept that
and I could not find a specific `@SuppressWarnings` annotation for this use case, therefore I decided to switch
the checks to `.equals()`.

Author: phoeinx

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/csv/CSVDialect.java

@@ -68,6 +68,7 @@ public CSVDialect(Object cls, Shape instanceShape) {
         super(cls, instanceShape);
     }
 
+
     public CSVDialect(Object cls, Shape instanceShape, String delimiter, boolean doubleQuote, String escapeChar,
                     String lineTerminator, String quoteChar, QuoteStyle quoting, boolean skipInitialSpace,
                     boolean strict) {
@@ -81,9 +82,9 @@ public CSVDialect(Object cls, Shape instanceShape, String delimiter, boolean dou
         this.skipInitialSpace = skipInitialSpace;
         this.strict = strict;
 
-        this.delimiterCodePoint = this.delimiter == NOT_SET ? NOT_SET_CODEPOINT : this.delimiter.codePointAt(0);
-        this.escapeCharCodePoint = this.escapeChar == NOT_SET ? NOT_SET_CODEPOINT : this.escapeChar.codePointAt(0);
-        this.quoteCharCodePoint = quoteChar.codePointAt(0); // quote char cannot be NOT_SET
+        this.delimiterCodePoint = this.delimiter.codePointAt(0); // delimiter cannot be NOT_SET
+        this.escapeCharCodePoint = this.escapeChar.equals(NOT_SET) ? NOT_SET_CODEPOINT : this.escapeChar.codePointAt(0);
+        this.quoteCharCodePoint = this.quoteChar.equals(NOT_SET) ? NOT_SET_CODEPOINT : this.quoteChar.codePointAt(0);
         this.lineTerminatorCodePoints = strToCodePointArray(this.lineTerminator);
     }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/csv/CSVDialectBuiltins.java

@@ -68,7 +68,7 @@ protected List<? extends NodeFactory<? extends PythonBuiltinBaseNode>> getNodeFa
     abstract static class DelimiterNode extends PythonUnaryBuiltinNode {
         @Specialization
         static Object doIt(CSVDialect self) {
-            return self.delimiter == NOT_SET ? PNone.NONE : self.delimiter;
+            return self.delimiter;
         }
     }
 
@@ -86,7 +86,7 @@ static boolean doIt(CSVDialect self) {
     abstract static class EscapeCharNode extends PythonUnaryBuiltinNode {
         @Specialization
         static Object doIt(CSVDialect self) {
-            return self.escapeChar == NOT_SET ? PNone.NONE : self.escapeChar;
+            return self.escapeChar.equals(NOT_SET) ? PNone.NONE : self.escapeChar;
         }
     }
 
@@ -104,7 +104,7 @@ static String doIt(CSVDialect self) {
     abstract static class QuoteCharNode extends PythonUnaryBuiltinNode {
         @Specialization
         static Object doIt(CSVDialect self) {
-            return self.quoteChar == NOT_SET ? PNone.NONE : self.quoteChar;
+            return self.quoteChar.equals(NOT_SET) ? PNone.NONE : self.quoteChar;
         }
     }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/csv/CSVModuleBuiltins.java

@@ -485,15 +485,15 @@ private Object createCSVDialect(VirtualFrame frame, PythonBuiltinClassType cls,
 
             /* validate options */
 
-            if (delimiter == NOT_SET) {
+            if (delimiter.equals(NOT_SET)) {
                 throw raise(TypeError, ErrorMessages.DELIMITER_MUST_BE_ONE_CHAR_STRING);
             }
 
             if (quotecharObj == PNone.NONE && quotingObj == PNone.NO_VALUE) {
                 quoting = QUOTE_NONE;
             }
 
-            if (quoting != QUOTE_NONE && quotechar == NOT_SET) {
+            if (quoting != QUOTE_NONE && quotechar.equals(NOT_SET)) {
                 throw raise(TypeError, ErrorMessages.QUOTECHAR_MUST_BE_SET_IF_QUOTING_ENABLED);
             }
 
@@ -543,7 +543,7 @@ private String getCharOrNone(String attribute, Object valueObj, String defaultVa
             if (valueObj == PNone.NO_VALUE) {
                 return defaultValue;
             }
-            if (valueObj == PNone.NONE || valueObj == NOT_SET) {
+            if (valueObj == PNone.NONE || valueObj.equals(NOT_SET)) {
                 return NOT_SET;
             }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/csv/CSVWriter.java

@@ -215,7 +215,7 @@ void joinAppend(String field, boolean quoted) {
                         }
                     }
                     if (wantEscape) {
-                        if (dialect.escapeChar == NOT_SET) {
+                        if (dialect.escapeChar.equals(NOT_SET)) {
                             throw PRaiseNode.getUncached().raise(PythonBuiltinClassType.CSVError, ErrorMessages.ESCAPE_WITHOUT_ESCAPECHAR);
                         }
                         this.rec.append(dialect.escapeChar);
@@ -235,7 +235,7 @@ void joinAppendLineterminator() {
         this.rec.append(this.dialect.lineTerminator);
     }
 
-    boolean containsCodePoint(int[] codePoints, int codePoint) {
+    private boolean containsCodePoint(int[] codePoints, int codePoint) {
         for (int cp : codePoints) {
             if (cp == codePoint) {
                 return true;