suppress handling of special characters in replacement text

[chesles]

Given replacement text with special characters like $, (, ), \, and probably others, the call to regex_replace was handling these - lines 107-117 seem to be a workaround for \, but using the boost::regex_constants::format_literal to suppress handling of all special characters in the replacement text seems like a better solution.

See also #17 and boost replace options documentation.

[mrtazz]

Oh good catch, thanks for this! Do you know if there is a corresponding flag for C++11? I'm planning to merge #19 and remove the boost dependency so it would be nice to not regress on this. But I'll anyway make sure to merge this before I remove boost, as there will be a last release depending on boost anyways. That way we have this fixed at least.

[chesles]

I'm not sure about a C++11 flag, I'll look into it and see if I can find one.

Doing a release with this fix before #19 gets merged sounds like a good approach to me.

[chesles]

It looks like there's not a corresponding flag for this in C++11 - the format string is controlled by the format_* flags described here, and none of them appear to be what we want for this.

However, by default regex_replace uses ECMAScript rules to evaluate the format string, and the only special character is $ (syntax reference here), so replacing $ with $$ on input strings should be all that's needed to get the correct behavior.

Here's a diff against #19 that implements this (and also removes code that seems to replace \\ with \\ - probably not needed unless I'm missing something there). I confirmed the tests added in this PR pass with this patch (only the dollar sign test fails without it, which is expected). @kylealanhale can you add this to your PR (or, what's the best way for me to add it?)

diff --git a/src/template.cpp b/src/template.cpp
index 7c43d03..23c49cb 100644
--- a/src/template.cpp
+++ b/src/template.cpp
@@ -154,24 +154,13 @@ std::string template_t::render_tags(const std::string& tmplate,
         trim(modifier);
         std::string text(start, matches[0].second);
         std::string repl;
+        std::string escaped_special_chars("$$$&");
+        std::regex special_chars("\\$");
+
         // don't html escape this
         if (modifier == "&" || modifier == "{")
         {
-            try
-            {
-                // get value
-                std::string s = ctx.get(key)[0][key];
-                // escape backslash in std::string
-                const std::string f = "\\";
-                size_t found = s.find(f);
-                while(found != std::string::npos)
-                {
-                    s.replace(found,f.length(),"\\");
-                    found = s.find(f, found+2);
-                }
-                repl.assign(s);
-            }
-            catch(int i) { repl.assign(""); }
+          repl.assign(ctx.get(key)[0][key]);
         }
         // this is a comment
         else if (modifier == "!")
@@ -193,6 +182,7 @@ std::string template_t::render_tags(const std::string& tmplate,
             }
             catch(int i) { repl.assign(""); }
         }
+        repl.assign(regex_replace(repl, special_chars, escaped_special_chars));

         // replace
         ret += regex_replace(text, tag, repl,