Move templates to their own crate

crates/templates/src/macros.rs

@@ -0,0 +1,102 @@
+// Copyright 2021 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// Count the number of tokens. Used to have a fixed-sized array for the
+/// templates list.
+macro_rules! count {
+    () => (0_usize);
+    ( $x:tt $($xs:tt)* ) => (1_usize + count!($($xs)*));
+}
+
+/// Macro that helps generating helper function that renders a specific template
+/// with a strongly-typed context. It also register the template in a static
+/// array to help detecting missing templates at startup time.
+///
+/// The syntax looks almost like a function to confuse syntax highlighter as
+/// little as possible.
+#[macro_export]
+macro_rules! register_templates {
+    {
+        $(
+            extra = { $( $extra_template:expr ),* };
+        )?
+
+        $(
+            // Match any attribute on the function, such as #[doc], #[allow(dead_code)], etc.
+            $( #[ $attr:meta ] )*
+            // The function name
+            pub fn $name:ident
+                // Optional list of generics. Taken from
+                // https://newbedev.com/rust-macro-accepting-type-with-generic-parameters
+                $(< $( $lt:tt $( : $clt:tt $(+ $dlt:tt )* )? ),+ >)?
+                // Type of context taken by the template
+                ( $param:ty )
+            {
+                // The name of the template file
+                $template:expr
+            }
+        )*
+    } => {
+        /// List of registered templates
+        static TEMPLATES: [(&'static str, &'static str); count!( $( $template )* )] = [
+            $( ($template, include_str!(concat!("res/", $template))) ),*
+        ];
+
+        /// List of extra templates used by other templates
+        static EXTRA_TEMPLATES: [(&'static str, &'static str); count!( $( $( $extra_template )* )? )] = [
+            $( $( ($extra_template, include_str!(concat!("res/", $extra_template))) ),* )?
+        ];
+
+        impl Templates {
+            $(
+                $(#[$attr])?
+                pub fn $name
+                    $(< $( $lt $( : $clt $(+ $dlt )* )? ),+ >)?
+                    (&self, context: &$param)
+                -> Result<String, TemplateError> {
+                    let ctx = Context::from_serialize(context)
+                        .map_err(|source| TemplateError::Context { template: $template, source })?;
+
+                    self.0.render($template, &ctx)
+                        .map_err(|source| TemplateError::Render { template: $template, source })
+                }
+            )*
+        }
+
+        /// Helps rendering each template with sample data
+        pub mod check {
+            use super::*;
+
+            $(
+                #[doc = concat!("Render the `", $template, "` template with sample contexts")]
+                pub fn $name
+                    $(< $( $lt $( : $clt $(+ $dlt )* + TemplateContext )? ),+ >)?
+                    (templates: &Templates)
+                -> anyhow::Result<()> {
+                    let samples: Vec< $param > = TemplateContext::sample();
+
+                    let name = $template;
+                    for sample in samples {
+                        let context = serde_json::to_value(&sample)?;
+                        ::tracing::info!(name, %context, "Rendering template");
+                        templates. $name (&sample)
+                            .with_context(|| format!("Failed to render template {:?} with context {}", name, context))?;
+                    }
+
+                    Ok(())
+                }
+            )*
+        }
+    };
+}