Add support to use single (' ') and double (" ") quotes to represent string

Author: Rajesh Jinaga

README.md

@@ -26,8 +26,8 @@ using Simpleflow;
 var script = 
 @" 
     # Declare and initialize variables
-    let text  = ""Hello, World! 🌄""
-    let today = $GetCurrentDateTime ( timezone: ""Eastern Standard Time"" )
+    let text  = 'Hello, World! 🌄'
+    let today = $GetCurrentDateTime ( timezone: 'Eastern Standard Time' )
 
     # Write rules
     rule when arg.UniversalId == 2 and (arg.New or arg.Verified)  then

src/Simpleflow/CodeGenerator/SimpleflowCodeVisitor.Helpers.cs

@@ -39,9 +39,12 @@ private Expression GetBoolExpression(string value)
             return Expression.Constant(Convert.ToBoolean(value), typeof(bool));
         }
 
-        private string GetUnquotedText(string @string)
+        private string GetUnquotedEscapeText(string @string)
         {
-            return @string.Substring(1, @string.Length - 2); // Trim first and last quotes
+            var text = @string.Substring(1, @string.Length - 2); // Trim first and last quotes
+            text = text.Replace("\\\"", "\"");
+            text = text.Replace("\\'", "'");
+            return text;
         }
 
         private ParameterExpression GetVariable(string name)

src/Simpleflow/CodeGenerator/SimpleflowCodeVisitor.VisitLiterals.cs

@@ -60,7 +60,7 @@ public override Expression VisitStringLiteral([NotNull] SimpleflowParser.StringL
         {
             var targetType = TargetTypeParserContextAnnotation.Get(context);
 
-            var value = GetUnquotedText(context.String().GetText());
+            var value = GetUnquotedEscapeText(context.String().GetText());
 
             if (targetType == null || targetType == typeof(string)) 
             {
@@ -100,11 +100,12 @@ public override Expression VisitTemplateStringLiteral([NotNull] SimpleflowParser
             StringBuilder sb = new StringBuilder();
             int index = 1; // First and last characters are back ticks
 
-            while(index < context.children.Count-1)
+
+            while (index < context.children.Count-1)
             {
                 var child = context.children[index];
 
-                if (child.GetChild(1) is SimpleflowParser.ObjectIdentifierContext)
+                if (child.GetChild(1) is SimpleflowParser.ExpressionContext)
                 {
                     if (sb.Length > 0)
                     {

src/Simpleflow/CodeGenerator/SimpleflowCodeVisitor.VistitSet.cs

@@ -38,7 +38,6 @@ public override Expression VisitSetStmt(SimpleflowParser.SetStmtContext context)
 
             // return expression
             return GetSetStmtExpression(context, variableName, variableExpression, valueExpression);
-
         }
 
         private Expression GetValueExpressionOfSetStmt(SimpleflowParser.SetStmtContext context, 
@@ -114,24 +113,24 @@ private Expression AssignWithHandlingError(Expression variable, Expression right
 
             // Add error variable without declare using let, error is exceptional case
             var errorVar = GetExistingOrAddVariableToGlobalScope(Expression.Variable(typeof(Exception), errorVariable));
-            var varFortryExpression = Expression.Variable(tryExpression.Type);
+            var varForTryExpression = Expression.Variable(tryExpression.Type);
 
             // Declare before use
-            DeclareVariable(varFortryExpression);
+            DeclareVariable(varForTryExpression);
 
             // Add variables
             if (variable == null)
             {
                 return Expression.Block(
-                     Expression.Assign(varFortryExpression, tryExpression), // run expression with try catch and capture value
-                     Expression.Assign(errorVar, Expression.Field(varFortryExpression, "Error"))
+                     Expression.Assign(varForTryExpression, tryExpression), // run expression with try catch and capture value
+                     Expression.Assign(errorVar, Expression.Field(varForTryExpression, "Error"))
                );
             }
 
             return Expression.Block(
-                        Expression.Assign(varFortryExpression, tryExpression), // run expression with try catch and capture value
-                        Expression.Assign(variable, Expression.Field(varFortryExpression, "Value")),
-                        Expression.Assign(errorVar, Expression.Field(varFortryExpression, "Error"))
+                        Expression.Assign(varForTryExpression, tryExpression), // run expression with try catch and capture value
+                        Expression.Assign(variable, Expression.Field(varForTryExpression, "Value")),
+                        Expression.Assign(errorVar, Expression.Field(varForTryExpression, "Error"))
                   );
         }
 

src/Simpleflow/Parser/Grammar/SimpleflowLexer.g4

@@ -68,7 +68,9 @@ True:               'true';
 False:              'false';
 Number:             ('+'|'-')?[0-9]+('.'[0-9]+)?;
 
-String:             '"' ( '\\"' | ~["\r\n] )*? '"';
+String:             '"' ( '\\"' | ~["\r\n] )*? '"'
+      |             '\'' ( '\\\'' | ~['\r\n] )*? '\'' ;
+      
 None:               'none' ;
 
 Identifier:         [_]*[a-zA-Z][_a-zA-Z0-9]* ;

src/Simpleflow/Parser/Grammar/SimpleflowParser.g4

@@ -94,7 +94,7 @@ templateStringLiteral
 
 templateStringAtom   
     : TemplateStringAtom
-    | TemplateStringStartExpression  objectIdentifier TemplateCloseBrace
+    | TemplateStringStartExpression  expression TemplateCloseBrace
     ;
 
 /** Function */
@@ -157,4 +157,3 @@ eos
     : EOF
     | {this.LineTerminatorAhead()}?
     ;
-