Vary headers, closes #14

README.md

@@ -76,6 +76,25 @@ any of your responses.
 | `HX-Trigger-After-Settle` | `HxResponseTrigger` | `axum_htmx::serde::HxEvent`         |
 | `HX-Trigger-After-Swap`   | `HxResponseTrigger` | `axum_htmx::serde::HxEvent`         |
 
+Also, there are corresponding cache-related headers, which you may want to add to
+`GET` responses, depending on the htmx headers.
+
+_For example, if your server renders the full HTML when the `HX-Request` header is
+missing or `false`, and it renders a fragment of that HTML when `HX-Request: true`,
+you need to add `Vary: HX-Request`. That causes the cache to be keyed based on a
+composite of the response URL and the `HX-Request` request header - rather than
+being based just on the response URL._
+
+Refer to [caching htmx docs section](https://htmx.org/docs/#caching) for details.
+
+| Header                  | Responder           |
+|-------------------------|---------------------|
+| `Vary: HX-Request`      | `VaryHxRequest`     |
+| `Vary: HX-Target`       | `VaryHxTarget`      |
+| `Vary: HX-Trigger`      | `VaryHxTrigger`     |
+| `Vary: HX-Trigger-Name` | `VaryHxTriggerName` |
+
+
 ## Request Guards
 
 __Requires features `guards`.__

src/responders.rs

@@ -11,6 +11,8 @@ mod location;
 pub use location::*;
 mod trigger;
 pub use trigger::*;
+mod vary;
+pub use vary::*;
 
 const HX_SWAP_INNER_HTML: &str = "innerHTML";
 const HX_SWAP_OUTER_HTML: &str = "outerHTML";

src/responders/vary.rs

@@ -0,0 +1,123 @@
+use axum_core::response::{IntoResponseParts, ResponseParts};
+use http::header::VARY;
+
+use crate::{extractors, headers, HxError};
+
+/// The `Vary: HX-Request` header.
+///
+/// You may want to add this header to the response if your handler responds differently based on
+/// the `HX-Request` request header.
+///
+/// For example, if your server renders the full HTML when the `HX-Request` header is missing or
+/// `false`, and it renders a fragment of that HTML when `HX-Request: true`.
+///
+/// You probably need this only for `GET` requests, as other HTTP methods are not cached by default.
+///
+/// See <https://htmx.org/docs/#caching> for more information.
+#[derive(Debug, Clone)]
+pub struct VaryHxRequest;
+
+impl IntoResponseParts for VaryHxRequest {
+    type Error = HxError;
+
+    fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
+        res.headers_mut()
+            .insert(VARY, headers::HX_REQUEST.try_into()?);
+
+        Ok(res)
+    }
+}
+
+impl extractors::HxRequest {
+    /// Convenience method to create the corresponding `Vary` response header
+    pub fn vary_response() -> VaryHxRequest {
+        VaryHxRequest
+    }
+}
+
+/// The `Vary: HX-Target` header.
+///
+/// You may want to add this header to the response if your handler responds differently based on
+/// the `HX-Target` request header.
+///
+/// You probably need this only for `GET` requests, as other HTTP methods are not cached by default.
+///
+/// See <https://htmx.org/docs/#caching> for more information.
+#[derive(Debug, Clone)]
+pub struct VaryHxTarget;
+
+impl IntoResponseParts for VaryHxTarget {
+    type Error = HxError;
+
+    fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
+        res.headers_mut()
+            .insert(VARY, headers::HX_TARGET.try_into()?);
+
+        Ok(res)
+    }
+}
+
+impl extractors::HxTarget {
+    /// Convenience method to create the corresponding `Vary` response header
+    pub fn vary_response() -> VaryHxTarget {
+        VaryHxTarget
+    }
+}
+
+/// The `Vary: HX-Trigger` header.
+///
+/// You may want to add this header to the response if your handler responds differently based on
+/// the `HX-Trigger` request header.
+///
+/// You probably need this only for `GET` requests, as other HTTP methods are not cached by default.
+///
+/// See <https://htmx.org/docs/#caching> for more information.
+#[derive(Debug, Clone)]
+pub struct VaryHxTrigger;
+
+impl IntoResponseParts for VaryHxTrigger {
+    type Error = HxError;
+
+    fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
+        res.headers_mut()
+            .insert(VARY, headers::HX_TRIGGER.try_into()?);
+
+        Ok(res)
+    }
+}
+
+impl extractors::HxTrigger {
+    /// Convenience method to create the corresponding `Vary` response header
+    pub fn vary_response() -> VaryHxTrigger {
+        VaryHxTrigger
+    }
+}
+
+/// The `Vary: HX-Trigger-Name` header.
+///
+/// You may want to add this header to the response if your handler responds differently based on
+/// the `HX-Trigger-Name` request header.
+///
+/// You probably need this only for `GET` requests, as other HTTP methods are not cached by default.
+///
+/// See <https://htmx.org/docs/#caching> for more information.
+#[derive(Debug, Clone)]
+pub struct VaryHxTriggerName;
+
+impl IntoResponseParts for VaryHxTriggerName {
+    type Error = HxError;
+
+    fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
+        res.headers_mut()
+            .insert(VARY, headers::HX_TRIGGER_NAME.try_into()?);
+
+        Ok(res)
+    }
+}
+
+impl extractors::HxTriggerName {
+    /// Convenience method to create the corresponding `Vary` response header
+    pub fn vary_response() -> VaryHxTriggerName {
+        VaryHxTriggerName
+    }
+}