Server side parameters via with_param

Fixes #142

src/lib.rs

@@ -5,7 +5,8 @@
 #[macro_use]
 extern crate static_assertions;
 
-use self::{error::Result, http_client::HttpClient};
+use self::{error::Result, http_client::HttpClient, sql::Bind};
+use ::serde::Serialize;
 use std::{collections::HashMap, fmt::Display, sync::Arc};
 
 pub use self::{compression::Compression, row::Row};
@@ -160,6 +161,12 @@ impl Client {
         self
     }
 
+    pub fn with_param(self, name: &str, value: impl Bind + Serialize) -> Result<Self, String> {
+        let mut param = String::from("");
+        Bind::write(&value, &mut param)?;
+        Ok(self.with_option(format!("param_{name}"), param))
+    }
+
     /// Used to specify a header that will be passed to all queries.
     ///
     /// # Example

src/query.rs

@@ -1,5 +1,5 @@
 use hyper::{header::CONTENT_LENGTH, Method, Request};
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use std::fmt::Display;
 use url::Url;
 
@@ -195,6 +195,12 @@ impl Query {
         self.client.add_option(name, value);
         self
     }
+
+    pub fn with_param(self, name: &str, value: impl Bind + Serialize) -> Result<Self, String> {
+        let mut param = String::from("");
+        Bind::write(&value, &mut param)?;
+        Ok(self.with_option(format!("param_{name}"), param))
+    }
 }
 
 /// A cursor that emits rows.

tests/it/query.rs

@@ -85,6 +85,31 @@ async fn fetch_one_and_optional() {
     assert_eq!(got_string, "bar");
 }
 
+#[tokio::test]
+async fn server_side_param() {
+    let client = prepare_database!()
+        .with_param("val1", 42)
+        .expect("failed to bind 42");
+
+    let result = client
+        .query("SELECT plus({val1: Int32}, {val2: String}) AS result")
+        .with_param("val2", 144)
+        .expect("failed to bind 144")
+        .fetch_one::<u64>()
+        .await
+        .expect("failed to fetch u64");
+    assert_eq!(result, 186);
+
+    let result = client
+        .query("SELECT {val1: String} AS result")
+        .with_param("param_val1", "string")
+        .expect("failed to bind \"string\"")
+        .fetch_one::<String>()
+        .await
+        .expect("failed to fetch string");
+    assert_eq!(result, "string");
+}
+
 // See #19.
 #[tokio::test]
 async fn long_query() {