Arduino <function> not declared in this scope (aka Arduino implicit forwarding declarations)

[Jadblack]

Hello everybody I am trying to compile this code with Arduino ide on a esp8266 but I get this error on line 45:
setup_wifi not declared in this scope
How can I fix it and however can someone help me to publish a reading of a rain sensor over Mqtt?

Thanks everyone

#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <Arduino.h>

#define WIFI_SSID "wifissid"
#define WIFI_PASSWORD "password"

#define MQTT_SERVER "10.25.73.8"
#define MQTT_PORT 1883 // use 8883 for SSL
#define MQTT_USER "pi" //user for Mosquitto
#define MQTT_PASSWORD "raspberry" //passord for Mosquitto

#define rain_topic "sensor/rain" //Topic Rain

const int sensorMin = 0; // sensor minimum
const int sensorMax = 1024; // sensor maximum

char message_buff[100];
bool debug = true;

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
Serial.begin(9600);
pinMode(A0, INPUT);
setup_wifi();
client.setServer(MQTT_SERVER, MQTT_PORT);
client.setCallback(callback);

//Connecfion WiFi
void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
Serial.println();
Serial.print("Connecting to ");
Serial.println(WIFI_SSID);
WiFi.mode(WIFI_STA);
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}

Serial.println("");
Serial.println("WiFi connected");
Serial.print("=> IP address: ");
Serial.print(WiFi.localIP());
Serial.println("");
}

//Reconnexion
void reconnect() {
while (!client.connected()) {
Serial.print("Attempting MQTT connection...");
// Attempt to connect
if (client.connect("ESP8266Client", MQTT_USER, MQTT_PASSWORD)) {
Serial.println("Connected");
} else {
Serial.print("Failed, Error: ");
Serial.print(client.state());
Serial.println(" Retrying MQTT connection in 5 seconds...");
delay(5000); // Wait 5 seconds before retrying
}
}
}

void loop() {
if (!client.connected())
{
reconnect();
}
client.loop();

int sensorReading = analogRead(A0);
int range = map(sensorReading, sensorMin, sensorMax, 0, 3);

// range value:
switch (range) {
case 0: // Sensor getting wet
Serial.println("Flood");
client.publish(rain_topic, "Flood", true);
break;
case 1: // Sensor getting wet
Serial.println("Rain Warning");
client.publish(rain_topic, "raining", true);
break;
case 2: // Sensor dry - To shut this up delete the " Serial.println("Not Raining"); " below.
Serial.println("Sun");
client.publish(rain_topic, "sun", true);
break;
}
delay(1000 * 10); // delay between reads

}

// Start after receiving the message
void callback(char* topic, byte* payload, unsigned int length) {
int i = 0;
if ( debug ) {
Serial.println("Message recu => topic: " + String(topic));
Serial.print(" | longueur: " + String(length, DEC));
}
// create character buffer with ending null terminator (string)
for (i = 0; i < length; i++) {
message_buff[i] = payload[i];
}
message_buff[i] = '\0';

String msgString = String(message_buff);
if ( debug ) {
Serial.println("Payload: " + msgString);
}
}

[d-a-v]

This is an Arduino code where it is not mandatory to declare function before their use.

This is made possible with an Arduino specific preprocessing on source code aimed at beginners and often counter-productive.

What you can do is adding this single line void setup_wifi(); before the setup(){ function.

Similar issue: https://community.platformio.org/t/code-works-in-arduino-ide-but-not-platformio/1907