Added feature testing functionality (bug 4021, r=pred).

plugins/include/console.inc

@@ -858,6 +858,8 @@ native RemoveServerTag(const String:tag[]);
  */
 functag public Action:CommandListener(client, const String:command[], argc);
 
+#define FEATURECAP_COMMANDLISTENER  "command listener"
+
 /**
  * Adds a callback that will fire when a command is sent to the server.
  *
@@ -866,6 +868,9 @@ functag public Action:CommandListener(client, const String:command[], argc);
  * Using Reg*Cmd to intercept is in poor practice, as it physically creates a
  * new command and can slow down dispatch in general.
  *
+ * To see if this feature is available, use FeatureType_Capability and 
+ * FEATURECAP_COMMANDLISTENER.
+ *
  * @param callback      Callback.
  * @param command		Command, or if not specified, a global listener.
  *                      The command is case insensitive.

plugins/include/core.inc

@@ -151,8 +151,22 @@ public Extension:__ext_core =
 
 native VerifyCoreVersion();
 
+/**
+ * Sets a native as optional, such that if it is unloaded, removed,
+ * or otherwise non-existent, the plugin will still work.  Calling
+ * removed natives results in a run-time error.
+ *
+ * @param name			Native name.
+ * @noreturn
+ */
+native MarkNativeAsOptional(const String:name[]);
+
 public __ext_core_SetNTVOptional()
 {
+	MarkNativeAsOptional("GetFeatureStatus");
+	MarkNativeAsOptional("RequireFeature");
+	MarkNativeAsOptional("AddCommandListener");
+	MarkNativeAsOptional("RemoveCommandListener");
 	VerifyCoreVersion();
 }
 

plugins/include/sourcemod.inc

@@ -410,16 +410,6 @@ native GetSysTickCount();
  */
 native AutoExecConfig(bool:autoCreate=true, const String:name[]="", const String:folder[]="sourcemod");
 
-/**
- * Sets a native as optional, such that if it is unloaded, removed,
- * or otherwise non-existent, the plugin will still work.  Calling
- * removed natives results in a run-time error.
- *
- * @param name			Native name.
- * @noreturn
- */
-native MarkNativeAsOptional(const String:name[]);
-
 /**
  * Registers a library name for identifying as a dependency to 
  * other plugins.
@@ -565,6 +555,81 @@ forward bool:OnClientFloodCheck(client);
  */
 forward OnClientFloodResult(client, bool:blocked);
 
+/**
+ * Feature types.
+ */
+enum FeatureType
+{
+	/**
+	 * A native function call.
+	 */
+	FeatureType_Native,
+	
+	/**
+	 * A named capability. This is distinctly different from checking for a
+	 * native, because the underlying functionality could be enabled on-demand
+	 * to improve loading time. Thus a native may appear to exist, but it might
+	 * be part of a set of features that are not compatible with the current game
+	 * or version of SourceMod.
+	 */
+	FeatureType_Capability
+};
+
+/**
+ * Feature statuses.
+ */
+enum FeatureStatus
+{
+	/**
+	 * Feature is available for use.
+	 */
+	FeatureStatus_Available,
+	
+	/**
+	 * Feature is not available.
+	 */
+	FeatureStatus_Unavailable,
+	
+	/**
+	 * Feature is not known at all.
+	 */
+	FeatureStatus_Unknown
+};
+
+/**
+ * Returns whether "GetFeatureStatus" will work. Using this native
+ * or this function will not cause SourceMod to fail loading on older versions,
+ * however, GetFeatureStatus will only work if this function returns true.
+ *
+ * @return              True if GetFeatureStatus will work, false otherwise.
+ */
+stock bool:CanTestFeatures()
+{
+	return LibraryExists("__CanTestFeatures__");
+}
+
+/**
+ * Returns whether a feature exists, and if so, whether it is usable.
+ *
+ * @param type          Feature type.
+ * @param name          Feature name.
+ * @return              Feature status.
+ */
+native FeatureStatus:GetFeatureStatus(FeatureType:type, const String:name[]);
+
+/**
+ * Requires that a given feature is available. If it is not, SetFailState()
+ * is called with the given message.
+ *
+ * @param type          Feature type.
+ * @param name          Feature name.
+ * @param fmt           Message format string, or empty to use default.
+ * @param ...           Message format parameters, if any.
+ * @noreturn
+ */
+native RequireFeature(FeatureType:type, const String:name[],
+                      const String:fmt[]="", any:...);
+
 #include <helpers>
 #include <entity>
 #include <entity_prop_stocks>

plugins/testsuite/capstest.sp

@@ -0,0 +1,33 @@
+
+
+public OnPluginStart()
+{
+	RegServerCmd("sm_test_caps1", Test_Caps1);
+	RegServerCmd("sm_test_caps2", Test_Caps2);
+	RegServerCmd("sm_test_caps3", Test_Caps3);
+}
+
+public Action:Test_Caps1(args)
+{
+	PrintToServer("CanTestFeatures: %d", CanTestFeatures());
+	PrintToServer("Status PTS: %d", GetFeatureStatus(FeatureType_Native, "PrintToServer"));
+	PrintToServer("Status ???: %d", GetFeatureStatus(FeatureType_Native, "???"));
+	PrintToServer("Status CL: %d", GetFeatureStatus(FeatureType_Capability, FEATURECAP_COMMANDLISTENER));
+
+	return Plugin_Handled
+}
+
+public Action:Test_Caps2(args)
+{
+	RequireFeature(FeatureType_Native, "VerifyCoreVersion");
+	RequireFeature(FeatureType_Native, "Sally ate a worm");
+}
+
+public Action:Test_Caps3(args)
+{
+	RequireFeature(FeatureType_Native, "Sally ate a worm", "oh %s %d no", "yam", 23);
+}
+
+
+
+