Update 'handlebars' to 3.0.

contrib/lib/Cargo.toml

@@ -52,7 +52,7 @@ serde_json = { version = "1.0.26", optional = true }
 rmp-serde = { version = "0.14.0", optional = true }
 
 # Templating dependencies.
-handlebars = { version = "2.0", optional = true }
+handlebars = { version = "3.0", optional = true }
 glob = { version = "0.3", optional = true }
 tera = { version = "1.0.2", optional = true }
 notify = { version = "4.0.6", optional = true }

contrib/lib/src/templates/engine.rs

@@ -62,7 +62,7 @@ pub struct Engines {
     /// `Tera` instance, ensure you use types imported from
     /// `rocket_contrib::templates::handlebars` to avoid version mismatches.
     #[cfg(feature = "handlebars_templates")]
-    pub handlebars: Handlebars,
+    pub handlebars: Handlebars<'static>,
 }
 
 impl Engines {
@@ -88,7 +88,7 @@ impl Engines {
                 None => return None
             },
             #[cfg(feature = "handlebars_templates")]
-            handlebars: match inner::<Handlebars>(templates) {
+            handlebars: match inner::<Handlebars<'static>>(templates) {
                 Some(hb) => hb,
                 None => return None
             },

contrib/lib/src/templates/handlebars_templates.rs

@@ -4,10 +4,10 @@ use crate::templates::{Engine, TemplateInfo};
 
 pub use crate::templates::handlebars::Handlebars;
 
-impl Engine for Handlebars {
+impl Engine for Handlebars<'static> {
     const EXT: &'static str = "hbs";
 
-    fn init(templates: &[(&str, &TemplateInfo)]) -> Option<Handlebars> {
+    fn init(templates: &[(&str, &TemplateInfo)]) -> Option<Handlebars<'static>> {
         let mut hb = Handlebars::new();
         for &(name, info) in templates {
             let path = &info.path;

examples/handlebars_templates/src/main.rs

@@ -56,7 +56,7 @@ fn wow_helper(
     h: &Helper<'_, '_>,
     _: &Handlebars,
     _: &Context,
-    _: &mut RenderContext<'_>,
+    _: &mut RenderContext<'_, '_>,
     out: &mut dyn Output
 ) -> HelperResult {
     if let Some(param) = h.param(0) {