Added a basic string escape (not 100% foolproof, but should catch pra…

…ctical cases)

src/plcdoc/st_declaration.tx

@@ -246,6 +246,21 @@ SemiColon:
 Anything that is considered a value: a literal, a variable, or e.g. a sum
 */
 Expression:
+   ExpressionString | ExpressionAnything
+;
+
+/*
+Because a string expression could use a syntax character, we need to make an effort match string content, to
+escape the content.
+
+We use a literal string match, instead of TextX's `STRING`, because we need to keep the quotes so we can later
+still distinguish a literal string type (over e.g. a variable name).
+*/
+ExpressionString:
+   /'.*'/
+;
+
+ExpressionAnything:
     /[^;]*/
     // Match anything, including parentheses, up to (but excluding) the semicolon
 ;

tests/plc_code/FB_Variables.txt

@@ -28,6 +28,10 @@ myfloat_no_ws:REAL;
     mystring_size5      : STRING(35) := 'Unknown';
     mystring_size6      : STRING[Module.SIZE] := 'Unknown';
 
+    mystring_escape     : STRING := ':;"';
+
+    mystring_concat     : STRING := CONCAT('abc', 'xyz');
+
     myint               : INT := SomeConstant;
     myint2              : INT := E_Error.NoError;
 

tests/test_st_grammar.py

@@ -124,6 +124,8 @@ def test_grammar_variables(meta_model):
             ("mystring_size4", "STRING[SIZE]", None, None, None, None),
             ("mystring_size5", "STRING(35)", "'Unknown'", None, None, None),
             ("mystring_size6", "STRING[Module.SIZE]", "'Unknown'", None, None, None),
+            ("mystring_escape", "STRING", "':;\"'", None, None, None),
+            ("mystring_concat", "STRING", "CONCAT('abc','xyz')", None, None, None),
             ("myint", "INT", "SomeConstant", None, None, None),
             ("myint2", "INT", "E_Error.NoError", None, None, None),
             ("mylist", "BOOL", None, None, "0..4", None),
@@ -151,7 +153,7 @@ def test_grammar_variables(meta_model):
             ("inline1", "INT", None, None, None, None),
         ]
 
-        assert len(variables) == 45
+        assert len(variables) == 47
 
         for i, expected in enumerate(expected_list):
             assert_variable(variables[i], expected)