minor #6241 [ExpressionLanguage] Add caution about backslash handling (zerustech, WouterJ)

xabbuh · xabbuh · commit 3165c70234b1 · 2016-02-07T11:42:30.000+01:00
This PR was merged into the 2.7 branch. Discussion ---------- [ExpressionLanguage] Add caution about backslash handling Finishes #5576 Original description: > Additional backslashes are required to escape a backslash(``\``) > in a string or regex because a string will be stripped by the lexer. > This should be documented here, otherwise, user may feel confused about > the unexpected behavior. > > | Q | A > | ------------- | --- > | Doc fix? | yes > | New docs? | no > | Applies to | ~2.4 > | Fixed tickets | n/a Commits ------- 31d74e5 Add a caution about backslash escaping 07f8e40 [components][expression_language] Add doc for backslashes
diff --git a/components/expression_language/syntax.rst b/components/expression_language/syntax.rst
@@ -20,6 +20,18 @@ The component supports:
 * **booleans** - ``true`` and ``false``
 * **null** - ``null``
 
+.. caution::
+
+    A backslash (``\``) must be escaped by 4 backslashes (``\\\\``) in a string
+    and 8 backslashes (``\\\\\\\\``) in a regex::
+
+        echo $language->evaluate('"\\\\"'); // prints \
+        $language->evaluate('"a\\\\b" matches "/^a\\\\\\\\b$/"'); // returns true
+
+    Control characters (e.g. ``\n``) in expressions are replaced with
+    whitespace. To avoid this, escape the sequence with a single backslash
+    (e.g.  ``\\n``).
+
 .. _component-expression-objects:
 
 Working with Objects
