ESP8266WebServer: pathArgs() to complement pathArg(N)

similar to ::args(), returns number of parsed path arguments
shortened esp8266#9100

Author: mcspr

libraries/ESP8266WebServer/examples/PathArgServer/PathArgServer.ino

@@ -16,6 +16,15 @@ const char *password = STAPSK;
 
 ESP8266WebServer server(80);
 
+bool checkPathArgs(int number) {
+  if (server.pathArgs() == number) {
+    return true;
+  }
+
+  server.send(500, "text/plain", "request handler received unexpected number of path arguments");
+  return false;
+}
+
 void setup(void) {
   Serial.begin(115200);
   WiFi.mode(WIFI_STA);
@@ -40,11 +49,19 @@ void setup(void) {
   });
 
   server.on(UriBraces("/users/{}"), []() {
+    if (!checkPathArgs(1)) {
+      return;
+    }
+
     String user = server.pathArg(0);
     server.send(200, "text/plain", "User: '" + user + "'");
   });
 
   server.on(UriRegex("^\\/users\\/([0-9]+)\\/devices\\/([0-9]+)$"), []() {
+    if (!checkPathArgs(2)) {
+      return;
+    }
+
     String user = server.pathArg(0);
     String device = server.pathArg(1);
     server.send(200, "text/plain", "User: '" + user + "' and Device: '" + device + "'");

libraries/ESP8266WebServer/src/ESP8266WebServer-impl.h

@@ -656,6 +656,13 @@ void ESP8266WebServerTemplate<ServerType>::_streamFileCore(const size_t fileSize
   send(200, contentType, emptyString);
 }
 
+template <typename ServerType>
+size_t ESP8266WebServerTemplate<ServerType>::pathArgs() const {
+  if (_currentHandler != nullptr)
+    return _currentHandler->pathArgs();
+  return 0;
+}
+
 template <typename ServerType>
 const String& ESP8266WebServerTemplate<ServerType>::pathArg(unsigned int i) const {
   if (_currentHandler != nullptr)

libraries/ESP8266WebServer/src/ESP8266WebServer.h

@@ -142,6 +142,8 @@ class ESP8266WebServerTemplate
   ServerType &getServer() { return _server; }
 
   const String& pathArg(unsigned int i) const; // get request path argument by number
+  int pathArgs() const; // get path arguments count
+
   const String& arg(const String& name) const;    // get request argument value by name
   const String& arg(int i) const;          // get request argument value by number
   const String& argName(int i) const;      // get request argument name by number

libraries/ESP8266WebServer/src/detail/RequestHandler.h

@@ -16,7 +16,7 @@ class RequestHandler {
     /*
         note: old handler API for backward compatibility
     */
-    
+
     virtual bool canHandle(HTTPMethod method, const String& uri) {
         (void) method;
         (void) uri;
@@ -43,7 +43,7 @@ class RequestHandler {
         return false;
     }
     virtual bool handle(WebServerType& server, HTTPMethod requestMethod, const String& requestUri) {
-        (void) server; 
+        (void) server;
         (void) requestMethod;
         (void) requestUri;
         return false;
@@ -74,7 +74,11 @@ class RequestHandler {
     std::vector<String> pathArgs;
 
 public:
-    const String& pathArg(unsigned int i) { 
+    size_t pathArgs() const {
+        return pathArgs.size();
+    }
+
+    const String& pathArg(unsigned int i) const {
         assert(i < pathArgs.size());
         return pathArgs[i];
     }