1 files changed, 21 insertions, 0 deletions
diff --git a/vendor/handlebars/src/output.rs b/vendor/handlebars/src/output.rs
index 67e62b849..12075b365 100644
--- a/vendor/handlebars/src/output.rs
+++ b/vendor/handlebars/src/output.rs
@@ -6,6 +6,19 @@ use std::string::FromUtf8Error;
 /// Handlebars uses this trait to define rendered output.
 pub trait Output {
     fn write(&mut self, seg: &str) -> Result<(), IOError>;
+
+    /// Designed to be used with `write!` macro.
+    /// for backward compatibility and to avoid breakage the default implementation
+    /// uses `format!` this may be not what you want.
+    fn write_fmt(&mut self, args: std::fmt::Arguments<'_>) -> Result<(), IOError> {
+        // Check if there is nothing to format to avoid allocation on case like
+        // write!(out, "hey")?;
+        if let Some(content) = args.as_str() {
+            self.write(content)
+        } else {
+            self.write(&std::fmt::format(args))
+        }
+    }
 }
 
 pub struct WriteOutput<W: Write> {
@@ -16,6 +29,10 @@ impl<W: Write> Output for WriteOutput<W> {
     fn write(&mut self, seg: &str) -> Result<(), IOError> {
         self.write.write_all(seg.as_bytes())
     }
+
+    fn write_fmt(&mut self, args: std::fmt::Arguments<'_>) -> Result<(), IOError> {
+        self.write.write_fmt(args)
+    }
 }
 
 impl<W: Write> WriteOutput<W> {
@@ -33,6 +50,10 @@ impl Output for StringOutput {
         self.buf.extend_from_slice(seg.as_bytes());
         Ok(())
     }
+
+    fn write_fmt(&mut self, args: std::fmt::Arguments<'_>) -> Result<(), IOError> {
+        self.buf.write_fmt(args)
+    }
 }
 
 impl StringOutput {