don't allow strange characters in unit type ids.

Using characters like " or ' in unit type ids has a high change of
breaking code, in particular the statistics code assumes that the
unit type ids can be used as wml varaible keys.

src/units/types.cpp

@@ -157,6 +157,8 @@ unit_type::unit_type(const config &cfg, const std::string & parent_id) :
 	animations_(),
 	build_status_(NOT_BUILT)
 {
+	check_id(id_);
+	check_id(base_id_);
 	gender_types_[0] = nullptr;
 	gender_types_[1] = nullptr;
 }
@@ -1287,6 +1289,28 @@ const unit_race *unit_type_data::find_race(const std::string &key) const
 	return i != races_.end() ? &i->second : nullptr;
 }
 
+void unit_type::check_id(std::string& id)
+{
+	assert(!id.empty());
+	//we don't allow leading whitepaces
+	if (id[0] == ' ') {
+		throw error("Found unit type id with a leading whitespace \"" + id + "\"");
+	}
+	bool gave_wanrning = false;
+	for (size_t pos = 0; pos < id.size(); ++pos) {
+		const char c = id[pos];
+		const bool valid = c == '_' || c == ' ' || (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9');
+		if (!valid) {
+			if (!gave_wanrning) {
+				ERR_UT << "Found unit type id with invalid chracters: \"" << id << "\"\n";
+				gave_wanrning = true;
+			}
+			id[pos] = '_';
+		}
+	}
+
+}
+
 unit_type_data unit_types;
 
 
@@ -1316,3 +1340,4 @@ void adjust_profile(std::string& profile)
 		profile = temp;
 	}
 }
+	static void check_id(std::string& id);

src/units/types.hpp

@@ -21,6 +21,7 @@
 #include "units/race.hpp"
 #include "units/attack_type.hpp"
 #include "util.hpp"
+#include "game_errors.hpp"
 
 #include <boost/noncopyable.hpp>
 #include <map>
@@ -38,6 +39,14 @@ typedef std::map<std::string, movetype> movement_type_map;
 class unit_type
 {
 public:
+	class error : public game::game_error
+	{
+	public:
+		error(const std::string& msg)
+			: game::game_error(msg)
+		{
+		}
+	};
 	/**
 	 * Creates a unit type for the given config, but delays its build
 	 * till later.
@@ -53,6 +62,7 @@ public:
 	/// These are in order of increasing levels of being built.
 	/// HELP_INDEX is already defined in a windows header under some conditions.
 	enum BUILD_STATUS {NOT_BUILT, CREATED, VARIATIONS, HELP_INDEXED, FULL};
+	static void check_id(std::string& id);
 private: // These will be called by build().
 	/// Load data into an empty unit_type (build to FULL).
 	void build_full(const movement_type_map &movement_types,

src/units/unit.cpp

@@ -195,11 +195,13 @@ void intrusive_ptr_release(const unit * u)
  */
 static const unit_type &get_unit_type(const std::string &type_id)
 {
-	if ( type_id.empty() )
-		throw game::game_error("creating unit with an empty type field");
-
-	const unit_type *i = unit_types.find(type_id);
-	if (!i) throw game::game_error("unknown unit type: " + type_id);
+	if (type_id.empty()) {
+		throw unit_type::error("creating unit with an empty type field");
+	}
+	std::string new_id = type_id;
+	unit_type::check_id(new_id);
+	const unit_type *i = unit_types.find(new_id);
+	if (!i) throw unit_type::error("unknown unit type: " + type_id);
 	return *i;
 }