feat: json filter

Cargo.lock

@@ -133,6 +133,8 @@ dependencies = [
  "itoap",
  "ryu",
  "sailfish-macros",
+ "serde",
+ "serde_json",
  "version_check",
 ]
 
@@ -159,18 +161,18 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.111"
+version = "1.0.118"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c9124df5b40cbd380080b2cc6ab894c040a3070d995f5c9dc77e18c34a8ae37d"
+checksum = "06c64263859d87aa2eb554587e2d23183398d617427327cf2b3d0ed8c69e4800"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.111"
+version = "1.0.118"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f2c3ac8e6ca1e9c80b8be1023940162bf81ae3cffbb1809474152f2ce1eb250"
+checksum = "c84d3526699cd55261af4b941e4e725444df67aa4f9e6a3564f18030d12672df"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -179,9 +181,9 @@ dependencies = [
 
 [[package]]
 name = "serde_json"
-version = "1.0.53"
+version = "1.0.60"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "993948e75b189211a9b31a7528f950c6adc21f9720b6438ff80a7fa2f864cea2"
+checksum = "1500e84d27fe482ed1dc791a56eddc2f230046a040fa908c08bda1d9fb615779"
 dependencies = [
  "itoa",
  "ryu",
@@ -190,9 +192,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.30"
+version = "1.0.41"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "93a56fabc59dce20fe48b6c832cc249c713e7ed88fa28b0ee0a3bfcaae5fe4e2"
+checksum = "6690e3e9f692504b941dc6c3b188fd28df054f7fb8469ab40680df52fdcc842b"
 dependencies = [
  "proc-macro2",
  "quote",

sailfish/Cargo.toml

@@ -15,11 +15,14 @@ edition = "2018"
 [features]
 default = ["derive", "perf-inline"]
 derive = ["sailfish-macros"]
+json = ["serde", "serde_json"]
 perf-inline = []
 
 [dependencies]
 itoap = "0.1.0"
 ryu = "1.0.4"
+serde = { version = "1.0.118", optional = true }
+serde_json = { version = "1.0.60", optional = true }
 
 [dependencies.sailfish-macros]
 path = "../sailfish-macros"

sailfish/src/runtime/filter.rs

@@ -146,6 +146,73 @@ pub fn trim<T: Render>(expr: &T) -> Trim<T> {
     Trim(expr)
 }
 
+cfg_json! {
+    pub struct Json<'a, T>(&'a T);
+
+    impl<'a, T: serde::Serialize> Render for Json<'a, T> {
+        #[inline]
+        fn render(&self, b: &mut Buffer) -> Result<(), RenderError> {
+            struct Writer<'a>(&'a mut Buffer);
+
+            impl<'a> std::io::Write for Writer<'a> {
+                #[inline]
+                fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+                    let buf = unsafe { std::str::from_utf8_unchecked(buf) };
+                    self.0.push_str(buf);
+                    Ok(buf.len())
+                }
+
+                #[inline]
+                fn write_all(&mut self, buf: &[u8]) -> std::io::Result<()> {
+                    self.write(buf).map(|_| {})
+                }
+
+                #[inline]
+                fn flush(&mut self) -> std::io::Result<()> {
+                    Ok(())
+                }
+            }
+
+            serde_json::to_writer(Writer(b), self.0)
+                .map_err(|e| RenderError::new(&e.to_string()))
+        }
+
+        #[inline]
+        fn render_escaped(&self, b: &mut Buffer) -> Result<(), RenderError> {
+            use super::escape::escape_to_buf;
+
+            struct Writer<'a>(&'a mut Buffer);
+
+            impl<'a> std::io::Write for Writer<'a> {
+                #[inline]
+                fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+                    let buf = unsafe { std::str::from_utf8_unchecked(buf) };
+                    escape_to_buf(buf, self.0);
+                    Ok(buf.len())
+                }
+
+                #[inline]
+                fn write_all(&mut self, buf: &[u8]) -> std::io::Result<()> {
+                    self.write(buf).map(|_| {})
+                }
+
+                #[inline]
+                fn flush(&mut self) -> std::io::Result<()> {
+                    Ok(())
+                }
+            }
+
+            serde_json::to_writer(Writer(b), self.0)
+                .map_err(|e| RenderError::new(&e.to_string()))
+        }
+    }
+
+    #[inline]
+    pub fn json<T: serde::Serialize>(expr: &T) -> Json<T> {
+        Json(expr)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

sailfish/src/runtime/utils.rs

@@ -1,5 +1,15 @@
 use std::ptr;
 
+macro_rules! cfg_json {
+    ($($item:item)*) => {
+        $(
+            #[cfg(feature = "json")]
+            #[cfg_attr(docsrs, doc(cfg(feature = "json")))]
+            $item
+        )*
+    }
+}
+
 #[cfg(sailfish_nightly)]
 macro_rules! likely {
     ($val:expr) => {