Try evaling js code client-side both with and without parentheses (#332)

* Try evaling jsHook verbatim. If that fails, try evaling in parentheses. Fixes #329

* throw existing error object rather than creating new ones

* tweak documentation of jsCode parameter

* if second try at eval is SyntaxError, then throw original error

* wrap eval strategy in a reusable function and leverage in evaluateStringMember

* update news; better comment; roxygenize

DESCRIPTION

@@ -25,4 +25,4 @@ Suggests:
 Enhances: shiny (>= 1.1)
 URL: https://github.com/ramnathv/htmlwidgets
 BugReports: https://github.com/ramnathv/htmlwidgets/issues
-RoxygenNote: 6.0.1
+RoxygenNote: 6.1.1

R/htmlwidgets.R

@@ -94,8 +94,8 @@ appendContent <- function(x, ...) {
 #'   multiple objects to pass to the function, use a named list.
 #' @return The modified widget object
 #'
-#' @details The \code{jsCode} parameter must be a valid JavaScript expression
-#'   that returns a function.
+#' @details The \code{jsCode} parameter must contain valid JavaScript code which
+#'   when evaluated returns a function.
 #'
 #'   The function will be invoked with three arguments: the first is the widget's
 #'   main HTML element, and the second is the data to be rendered (the \code{x}

inst/NEWS

@@ -1,3 +1,9 @@
+htmlwidgets 1.4
+-----------------------------------------------------------------------
+
+* JavaScript statements can now be passed along to `onRender()` and `JS()` (#329).
+
+
 htmlwidgets 1.3
 -----------------------------------------------------------------------
 

inst/www/htmlwidgets.js

@@ -233,7 +233,7 @@
           theseArgs = theseArgs.concat([task.data]);
           task = task.code;
         }
-        var taskFunc = eval("(" + task + ")");
+        var taskFunc = tryEval(task);
         if (typeof(taskFunc) !== "function") {
           throw new Error("Task must be a function! Source:\n" + task);
         }
@@ -242,6 +242,31 @@
     }
   }
 
+  // Attempt eval() both with and without enclosing in parentheses.
+  // Note that enclosing coerces a function declaration into
+  // an expression that eval() can parse
+  // (otherwise, a SyntaxError is thrown)
+  function tryEval(code) {
+    var result = null;
+    try {
+      result = eval(code);
+    } catch(error) {
+      if (!error instanceof SyntaxError) {
+        throw error;
+      }
+      try {
+        result = eval("(" + code + ")");
+      } catch(e) {
+        if (e instanceof SyntaxError) {
+          throw error;
+        } else {
+          throw e;
+        }
+      }
+    }
+    return result;
+  }
+
   function initSizing(el) {
     var sizing = sizingPolicy(el);
     if (!sizing)
@@ -732,7 +757,7 @@
       if (o !== null && typeof o === "object" && part in o) {
         if (i == (l - 1)) { // if we are at the end of the line then evalulate
           if (typeof o[part] === "string")
-            o[part] = eval("(" + o[part] + ")");
+            o[part] = tryEval(o[part]);
         } else { // otherwise continue to next embedded object
           o = o[part];
         }