Reimplement example, compile only with "json" feature enabled

Signed-off-by: Matthias Beyer <mail@beyermatthias.de>

Author: matthiasbeyer

examples/async_source/main.rs

@@ -1,72 +1,84 @@
-use std::error::Error;
+#[cfg(feature = "json")]
+mod example {
+    use std::error::Error;
 
-use config::{builder::AsyncState, AsyncSource, ConfigBuilder, ConfigError, FileFormat, Map};
+    use config::{builder::AsyncState, AsyncSource, ConfigBuilder, ConfigError, FileFormat, Map};
 
-use async_trait::async_trait;
-use futures::{select, FutureExt};
-use warp::Filter;
+    use async_trait::async_trait;
+    use futures::{select, FutureExt};
+    use warp::Filter;
 
-// Example below presents sample configuration server and client.
-//
-// Server serves simple configuration on HTTP endpoint.
-// Client consumes it using custom HTTP AsyncSource built on top of reqwest.
+    // Example below presents sample configuration server and client.
+    //
+    // Server serves simple configuration on HTTP endpoint.
+    // Client consumes it using custom HTTP AsyncSource built on top of reqwest.
 
-#[tokio::main]
-async fn main() -> Result<(), Box<dyn Error>> {
-    select! {
-        r = run_server().fuse() => r,
-        r = run_client().fuse() => r
-    }
-}
 
-async fn run_server() -> Result<(), Box<dyn Error>> {
-    let service = warp::path("configuration").map(|| r#"{ "value" : 123 }"#);
+    async fn run_server() -> Result<(), Box<dyn Error>> {
+        let service = warp::path("configuration").map(|| r#"{ "value" : 123 }"#);
 
-    println!("Running server on localhost:5001");
+        println!("Running server on localhost:5001");
 
-    warp::serve(service).bind(([127, 0, 0, 1], 5001)).await;
+        warp::serve(service).bind(([127, 0, 0, 1], 5001)).await;
 
-    Ok(())
-}
+        Ok(())
+    }
 
-async fn run_client() -> Result<(), Box<dyn Error>> {
-    // Good enough for an example to allow server to start
-    tokio::time::sleep(tokio::time::Duration::from_secs(3)).await;
+    async fn run_client() -> Result<(), Box<dyn Error>> {
+        // Good enough for an example to allow server to start
+        tokio::time::sleep(tokio::time::Duration::from_secs(3)).await;
 
-    let config = ConfigBuilder::<AsyncState>::default()
-        .add_async_source(HttpSource {
-            uri: "http://localhost:5001/configuration".into(),
-            format: FileFormat::Json,
-        })
-        .build()
-        .await?;
+        let config = ConfigBuilder::<AsyncState>::default()
+            .add_async_source(HttpSource {
+                uri: "http://localhost:5001/configuration".into(),
+                format: FileFormat::Json,
+            })
+            .build()
+            .await?;
 
-    println!("Config value is {}", config.get::<String>("value")?);
+        println!("Config value is {}", config.get::<String>("value")?);
 
-    Ok(())
-}
+        Ok(())
+    }
 
-// Actual implementation of AsyncSource can be found below
+    // Actual implementation of AsyncSource can be found below
+
+    #[derive(Debug)]
+    struct HttpSource {
+        uri: String,
+        format: FileFormat,
+    }
+
+    #[async_trait]
+    impl AsyncSource for HttpSource {
+        async fn collect(&self) -> Result<Map<String, config::Value>, ConfigError> {
+            reqwest::get(&self.uri)
+                .await
+                .map_err(|e| ConfigError::Foreign(Box::new(e)))? // error conversion is possible from custom AsyncSource impls
+                .text()
+                .await
+                .map_err(|e| ConfigError::Foreign(Box::new(e)))
+                .and_then(|text| {
+                    self.format
+                        .parse(Some(&self.uri), &text)
+                        .map_err(|e| ConfigError::Foreign(e))
+                })
+        }
+    }
 
-#[derive(Debug)]
-struct HttpSource {
-    uri: String,
-    format: FileFormat,
 }
 
-#[async_trait]
-impl AsyncSource for HttpSource {
-    async fn collect(&self) -> Result<Map<String, config::Value>, ConfigError> {
-        reqwest::get(&self.uri)
-            .await
-            .map_err(|e| ConfigError::Foreign(Box::new(e)))? // error conversion is possible from custom AsyncSource impls
-            .text()
-            .await
-            .map_err(|e| ConfigError::Foreign(Box::new(e)))
-            .and_then(|text| {
-                self.format
-                    .parse(Some(&self.uri), &text)
-                    .map_err(|e| ConfigError::Foreign(e))
-            })
+#[cfg(feature = "json")]
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    select! {
+        r = example::run_server().fuse() => r,
+        r = example::run_client().fuse() => r
     }
 }
+
+#[cfg(not(feature = "json"))]
+fn main() {
+    println!("This example needs the 'json' feature enabled");
+}
+